Cylindrical battery and preparation method thereof

Abstract

The invention provides a cylindrical battery and a preparation method thereof, and relates to the technical field of lithium ion batteries. The cylindrical battery sequentially comprises a dry-type positive pole group, an isolating membrane and a dry-type negative pole group from inside to outside; the dry type positive electrode group comprises a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector; the dry-type negative electrode group comprises a negative electrode current collector and a negative electrode active layer arranged on at least one surface of the negative electrode current collector; the positive current collector is provided with a central cylinder and a plurality of blades coaxially connected to the side surface of the central cylinder, the plurality of blades are respectively positioned on a plane passing through the axis of the central cylinder, the central cylinder is arranged along the axial direction of the cylindrical battery, and the plurality of blades are arranged at intervals; and the negative current collector is a metal shell of the cylindrical battery. The cylindrical battery adopts a dry electrode and a current collector with a special structure, does not need a winding process, and has the advantages of low cost, stable performance, high energy density and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a cylindrical battery and a preparation method thereof. Background Art

[0002] Cylindrical lithium batteries have been widely used in electronic equipment, power tools, electric vehicles and other fields due to their advantages such as good monomer consistency, excellent mechanical properties, high temperature resistance and high safety. Existing cylindrical lithium batteries mostly use a wet winding process. The preparation process mainly includes ingredients, coating, rolling, striping, film making, winding, shelling, welding, baking, liquid injection, packaging, formation, capacity division and screening process steps. The manufacturing process is long and complicated. In addition, traditional cylindrical lithium batteries need to be wound with a winding needle. After the winding needle is pulled out, there is a gap inside the winding core. During the cycle, the force in the gap is inconsistent with other areas, and the positive and negative electrodes are not tightly fitted. It is easy to fail and lithium precipitate. After lithium precipitate, the limited electrolyte will be consumed, resulting in insufficient electrolyte, which further causes lithium precipitate in the battery, triggering a vicious cycle and causing poor battery performance. Summary of the invention

[0003] The cylindrical battery provided by the present invention adopts dry electrodes and a current collector with a special structure, does not require a winding process, avoids gaps inside the battery and also saves current collector materials, and has the advantages of low cost, stable performance, high energy density, etc.

[0004] The present invention also provides a method for preparing a cylindrical battery, which can prepare the cylindrical battery and has the advantages of simple process, material saving and environmental protection.

[0005] In a first aspect, the present invention provides a cylindrical battery, which comprises, from the inside to the outside, a dry positive electrode group, a separator and a dry negative electrode group; the dry positive electrode group comprises a positive electrode collector and a positive electrode active layer disposed on at least one surface of the positive electrode collector; the dry negative electrode group comprises a negative electrode collector and a negative electrode active layer disposed on at least one surface of the negative electrode collector; The positive electrode current collector has a central cylinder and a plurality of blades coaxially connected to the side of the central cylinder, the plurality of blades are respectively located on planes passing through the axis of the central cylinder, the central cylinder is arranged along the axial direction of the cylindrical battery, and the plurality of blades are arranged at intervals from each other; the negative electrode current collector is the metal shell of the cylindrical battery.

[0006] In the cylindrical battery as described above, the plurality of blades are symmetrically arranged in pairs with the central cylinder as the axis of symmetry.

[0007] The cylindrical battery as described above, wherein positive electrode active layers are disposed on both surfaces of the plurality of blades.

[0008] The cylindrical battery as described above, wherein the number of the blades is 2 or more.

[0009] In the cylindrical battery as described above, the blades are in a rectangular or square shape.

[0010] The cylindrical battery as described above, wherein the blade has a hollow structure.

[0011] The cylindrical battery as described above, wherein the number of the blades is 4, 6, 8 or 10.

[0012] The cylindrical battery as described above, wherein the height of the blades is the same as the height of the central cylinder.

[0013] The cylindrical battery as described above, wherein the thickness of the blade is 3-9 μm.

[0014] In the cylindrical battery as described above, the width of the blade is 1 / 2-2 / 3 of the inner diameter of the cylindrical battery.

[0015] In the cylindrical battery as described above, the central cylinder has a hollow structure, and the cylinder wall of the central cylinder has a hollow structure.

[0016] The cylindrical battery as described above, wherein the inner diameter of the central cylinder is 0-3 mm, and the outer diameter is 0.5-3.2 mm.

[0017] The cylindrical battery as described above, wherein the height of the central cylinder is 15-30 mm lower than the height of the metal shell.

[0018] The cylindrical battery as described above, wherein a positive electrode active layer is disposed on the outer surface of the central cylinder.

[0019] The cylindrical battery as described above, wherein the positive electrode active layer has N positive electrode functional active layers, N≥2.

[0020] The N positive electrode functional active layers have a gradient porosity, and the porosity gradually increases from the positive electrode current collector to the surface of the positive electrode active layer.

[0021] The cylindrical battery as described above, wherein the negative electrode active layer has N negative electrode functional active layers, N≥1.

[0022] The N negative electrode functional active layers have a gradient porosity, and the porosity gradually increases from the negative electrode current collector to the surface of the negative electrode active layer.

[0023] In the cylindrical battery as described above, the material of the positive electrode current collector is aluminum foil or copper foil.

[0024] In a second aspect, the present invention provides a method for preparing a cylindrical battery, comprising the following steps: S1, the raw materials of the positive electrode active layer are mixed and fiberized to obtain a positive electrode mixture; the raw materials of the negative electrode active layer are mixed and fiberized to obtain a negative electrode mixture; S2, pressing the negative electrode mixture described in step S1 onto the metal shell of the cylindrical battery to obtain a negative electrode group; pressing the positive electrode mixture described in step S1 into a positive electrode collector to obtain a positive electrode group; the positive electrode collector has a central cylinder and a plurality of blades coaxially connected to the side of the central cylinder, and the plurality of blades are spaced apart from each other; S3, putting a separator on the positive electrode assembly of step S2 and assembling it with the negative electrode, so that the central cylinder of the positive electrode collector is arranged along the axial direction of the cylindrical battery, and then drying, injecting liquid, closing the cover, pressing and forming, standing, forming, dividing the capacity and screening to obtain a cylindrical battery.

[0025] In the method for preparing a cylindrical battery as described above, the raw materials of the positive electrode active layer include a positive electrode active material, a binder, a conductive agent and a pore former.

[0026] Furthermore, the positive electrode active material, the binder and the conductive agent are firstly mixed evenly, and then the pore former is added and mixed evenly to obtain the positive electrode mixture.

[0027] Furthermore, the positive electrode mixture is divided into N parts, the N parts of the positive electrode mixture have different contents of the pore former, and the N parts of the positive electrode mixture are pressed on the positive electrode current collector in order from low to high content of the pore former.

[0028] In the method for preparing a cylindrical battery as described above, the raw materials of the negative electrode active layer include a negative electrode active material, a binder, a conductive agent and a pore former.

[0029] Furthermore, the negative electrode active material, the binder and the conductive agent are firstly mixed evenly, and then the pore former is added and mixed evenly to obtain the negative electrode mixture.

[0030] Furthermore, the negative electrode mixture is divided into N parts, the N parts of the negative electrode mixture have different contents of pore formers, and the N parts of the positive and negative electrode mixtures are pressed on the negative electrode current collector in order of the content of the pore formers from low to high.

[0031] The pore former includes at least one of LiFSI, LiTFSI and LiPO2F2.

[0032] The reagents and raw materials used in the present invention are commercially available.

[0033] The cylindrical battery provided by the present invention adopts a characteristically designed positive electrode current collector in a dry positive electrode group and locates it inside the cylindrical battery. The central cylinder and multiple blades of the positive electrode current collector can play a good supporting role, preventing the problem of battery lithium precipitation caused by uneven force on the negative electrode; and the cylindrical battery provided by the present invention does not need to adopt a winding process, which reduces the amount of current collector used and reduces the cost of the battery; and the cylindrical battery provided by the present invention uses the metal shell of the cylindrical battery as the negative electrode current collector, so there is no need to weld the pole ear on the negative electrode current collector, which saves space, is conducive to improving the energy density of the battery, and also avoids the problem of easy battery failure caused by uneven force on the pole ear position. Compared with the traditional wound cylindrical battery, the cylindrical battery provided by the present invention has the advantages of low cost, stable performance, and high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the cylindrical battery in Example 1.

[0035] Figure 2 Schematic diagram of the structure of the positive electrode current collector used in Example 1.

[0036] Figure 3 This is a top view of the positive electrode current collector used in Example 1.

[0037] Figure 4 Schematic diagram of the structure of the cylindrical battery in Example 2.

[0038] Figure 5 Schematic diagram of the structure of the positive electrode current collector used in Example 2.

[0039] Figure 6 This is a top view of the positive electrode current collector used in Example 2.

[0040] Description of reference numerals: 1-positive electrode current collector, 2-positive electrode active layer, 3-separator, 4-negative electrode active layer, 5-metal shell, 6-center cylinder, 7-blade, 8-positive electrode ear. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0042] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0043] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventionally understood meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments is carried out in accordance with the protocols and parameters given by the manufacturer.

[0044] In the first aspect, the present invention provides a cylindrical battery, which comprises, from the inside to the outside, a dry positive electrode group, a separator 3 and a dry negative electrode group; the dry positive electrode group comprises a positive electrode collector 1 and a positive electrode active layer 2 arranged on at least one surface of the positive electrode collector 1; the dry negative electrode group comprises a negative electrode collector and a negative electrode active layer 4 arranged on at least one surface of the negative electrode collector; The positive electrode current collector 1 has a central cylinder 6 and a plurality of blades 7 coaxially connected to the side of the central cylinder 6, wherein the plurality of blades 7 are respectively located on planes passing through the axis of the central cylinder 6, the central cylinder 6 is arranged along the axial direction of the cylindrical battery, and the plurality of blades 7 are arranged at intervals from each other; the negative electrode current collector is the metal shell 5 of the cylindrical battery.

[0045] The cylindrical battery provided by the present invention adopts a characteristically designed positive electrode current collector in a dry positive electrode group and locates it inside the cylindrical battery. The central cylinder and multiple blades of the positive electrode current collector can play a good supporting role, preventing the problem of battery lithium precipitation caused by uneven force on the negative electrode; and the cylindrical battery provided by the present invention does not need to adopt a winding process, which reduces the amount of current collector used and reduces the cost of the battery; and the cylindrical battery provided by the present invention uses the metal shell of the cylindrical battery as the negative electrode current collector, so there is no need to weld the pole ear on the negative electrode current collector, which saves space, is conducive to improving the energy density of the battery, and also avoids the problem of easy failure of the battery caused by uneven force on the pole ear position. Compared with the traditional wound cylindrical battery with a gap in the middle, the cylindrical battery provided by the present invention has the advantages of low cost, stable performance, high energy density, etc.

[0046] In the present invention, the plurality of blades 7 can be arranged symmetrically in pairs with the central cylinder 6 as the symmetry axis, or can be arranged asymmetrically. In some embodiments of the present invention, the plurality of blades 7 are symmetrically distributed in pairs with the central cylinder 6 as the symmetry axis, which is more conducive to charge transfer in the battery.

[0047] In the present invention, positive electrode active layers 4 are disposed on both surfaces of the plurality of blades 7 , which is beneficial to increasing the area of ​​the positive electrode active layers 4 .

[0048] In the present invention, the number of blades 7 is not limited. In some embodiments of the present invention, the number of blades 7 is 2 or more, preferably 4, 6, 8 or 10, and most preferably 6. The more blades 7 there are, the more conducive it is to reducing electronic resistance, but it will also reduce the energy density of the battery. When the number of blades 7 is 6, the battery has the best rate, capacity and cycle performance.

[0049] In the present invention, the height of the blade 7 may be the same as the height of the central cylinder 6, or may be less than the height of the central cylinder 7. In some embodiments of the present invention, the height of the blade 7 is the same as the height of the central cylinder 6, which may provide further support.

[0050] In the present invention, the thickness of the blade 7 is not limited. In some embodiments of the present invention, the thickness of the blade 7 is 3-9 μm, which can have both good mechanical properties and electronic transmission properties.

[0051] In the present invention, the width of the blade 7 can be adjusted according to the size of the cylindrical battery. In some embodiments of the present invention, the width of the blade 7 is 1 / 2-2 / 3 of the inner diameter of the cylindrical battery, which can match the size of commonly used cylindrical batteries.

[0052] In the present invention, the shape of the blade 7 is not limited. In some embodiments of the present invention, the shape of the blade 7 is rectangular or square, which can make fuller use of the internal space of the cylindrical battery.

[0053] In the present invention, the blade 7 may have a hollow structure or a solid structure. In some embodiments of the present invention, the blade 7 has a hollow structure, which is more conducive to the transmission of electrons.

[0054] In the present invention, the central cylinder 6 can be a solid structure or a hollow structure. In some embodiments of the present invention, the central cylinder 6 is a hollow structure, and the cylinder wall of the central cylinder 6 has a perforated structure, which is not only conducive to saving materials and reducing the weight of the battery, but also convenient for electrolyte layer transmission. Furthermore, the outer diameter and inner diameter of the central cylinder 6 with a hollow structure can be adjusted according to the size of the cylindrical battery.

[0055] In some preferred embodiments of the present invention, the outer diameter of the central cylinder 6 is 0.5-3.2 mm and the inner diameter is 0-3 mm, which can match the size of commonly used cylindrical batteries and provide sufficient supporting performance.

[0056] In the present invention, the height of the central cylinder 6 can be adjusted according to the height of the cylindrical battery. In some embodiments of the present invention, the height of the central cylinder 6 is 15-30 mm lower than the height of the metal shell, which can match the size of commonly used cylindrical batteries.

[0057] The present invention does not specifically limit the material of the positive electrode current collector 1, and the material of the positive electrode current collector 1 can be a commonly used material in the art. In some embodiments of the present invention, the material of the positive electrode current collector 1 is aluminum foil or copper foil, which has good conductivity, light weight and low price.

[0058] In the present invention, the positive electrode active layer 2 may be a single layer structure or a multilayer structure. In some embodiments of the present invention, the positive electrode active layer 2 has N positive electrode functional active layers, N≥2, and multiple functional active layers may be provided according to the performance requirements of the battery.

[0059] In some preferred embodiments of the present invention, the N positive electrode functional active layers have a gradient porosity, and the porosity gradually increases along the surface direction from the positive electrode current collector 1 to the positive electrode active layer 2, which is beneficial to the transmission of lithium ions and improves the performance of the battery.

[0060] In the present invention, the negative electrode active layer 4 may be a single layer structure or a multilayer structure. In some embodiments of the present invention, the negative electrode active layer 4 has N negative electrode functional active layers, N≥2, and multiple functional active layers may be provided according to the performance requirements of the battery.

[0061] In some preferred embodiments of the present invention, the N negative electrode functional active layers have a gradient porosity, and the porosity gradually increases along the direction from the negative electrode current collector to the surface of the negative electrode active layer 4, which is beneficial to the transmission of lithium ions and improves the performance of the battery.

[0062] In a second aspect, the present invention provides a method for preparing a cylindrical battery, comprising the following steps: S1. The raw materials of the positive electrode active layer are mixed and fiberized to obtain a positive electrode mixture; the raw materials of the negative electrode active layer are mixed and fiberized to obtain a negative electrode mixture; S2, pressing the negative electrode mixture in step S1 onto a metal shell of a cylindrical battery to obtain a negative electrode group; pressing the positive electrode mixture in step S1 onto a positive electrode collector to obtain a positive electrode group; the positive electrode collector has a central cylinder and a plurality of blades coaxially connected to the side of the central cylinder, and the plurality of blades are spaced apart from each other; S3, putting a separator on the positive electrode assembly in step S2 and assembling it with the negative electrode, the central cylinder of the positive electrode collector is arranged along the axial direction of the cylindrical battery, and then drying, injecting liquid, closing the cover, pressing, standing, forming, dividing the capacity and screening are carried out to obtain a cylindrical battery.

[0063] The preparation method of the cylindrical battery provided by the present invention eliminates the need for winding, negative electrode tabs and welding of positive electrode tabs, which not only saves current collector materials but also simplifies the process; and the preparation process does not require the use of organic solvents such as N-methylpyrrolidone (NVP), which is more environmentally friendly.

[0064] In the present invention, the raw material of the positive electrode active layer can be a common raw material of the positive electrode active layer in the art. In some embodiments of the present invention, the raw material of the positive electrode active layer includes a positive electrode active material, a binder, a conductive agent and a pore former, the active material is used to generate an electrochemical reaction to ensure that the battery can be charged and discharged normally, the binder is used to shape the active layer and improve the mechanical properties of the active layer, thereby improving the mechanical properties of the positive electrode and extending the life of the battery; the conductive agent is used to transmit electrons and improve the electron transmission performance of the positive electrode.

[0065] In some preferred embodiments of the present invention, the positive electrode active material, the binder and the conductive agent are first mixed uniformly, and then the pore former is added and mixed uniformly to obtain a positive electrode mixture. Such a mixing method can make the pore former dispersed more uniformly in the positive electrode mixture, which is beneficial to make the pore distribution in the positive electrode active layer more uniform, further improve the cycle performance of the battery and prevent the lithium deposition of the battery, and can improve the stability of the preparation method.

[0066] In some preferred embodiments of the present invention, the positive electrode mixture is divided into N parts, the content of the pore former in the N parts of the positive electrode mixture is different, and the N parts of the positive electrode mixture are pressed on the positive electrode current collector in order from low to high content of the pore former. The positive electrode active layer is prepared using positive electrode mixtures with different pore former contents, and a positive electrode active layer with a gradient porosity can be formed, and the porosity gradually increases from the negative electrode current collector to the surface of the negative electrode active layer.

[0067] In the present invention, the raw material of the negative electrode active layer can be a common raw material of the negative electrode active layer in the art. In some embodiments of the present invention, the raw material of the negative electrode active layer includes a negative electrode active material, a binder, a conductive agent and a pore former.

[0068] In some preferred embodiments of the present invention, the negative electrode active material, the binder and the conductive agent are first mixed uniformly, and then the pore former is added and mixed uniformly to obtain a negative electrode mixture. Such a mixing method can make the pore former dispersed more uniformly in the negative electrode mixture, which is beneficial to make the pore distribution in the negative electrode active layer more uniform, further improve the cycle performance of the battery and prevent the lithium deposition of the battery, and can improve the stability of the preparation method.

[0069] In some preferred embodiments of the present invention, the negative electrode mixture is divided into N parts, the content of the pore former in the N parts of the negative electrode mixture is different, and the N parts of the negative electrode mixture are pressed on the positive electrode current collector in order from low to high content of the pore former. The negative electrode active layer is prepared using negative electrode mixtures with different pore former contents, and a negative electrode active layer with a gradient porosity can be formed, and the porosity gradually increases from the negative electrode current collector to the surface of the negative electrode active layer.

[0070] In the present invention, the pore former may be a pore former commonly used in the art. In some embodiments of the present invention, the pore former includes at least one of LiFSI, LiTFSI and LiPO2F2. When the pore former includes a lithium salt, the electrolyte dissolves the lithium salt in the functional active layer, thereby making the functional active layer have more pores, and during the charge and discharge process of the battery, the lithium salt can also replenish lithium for the electrode, thereby preventing the problem of shortening the battery life due to lithium deficiency in the electrode.

[0071] The technical scheme of the present invention is further illustrated below in conjunction with specific examples. All parts, percentages, and ratios described in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0072] Example 1

[0073] This embodiment provides a cylindrical battery. Figure 1 The schematic diagram of the structure of the cylindrical battery provided in Example 1 shows that the cylindrical battery includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0074] Figure 2Schematic diagram of the structure of the positive electrode collector used in Example 1. It can be seen from the figure that the positive electrode collector 1 is composed of a central cylinder 6 and two blades 7 coaxially connected to the side of the central cylinder 6. The two blades 7 are symmetrically distributed on a plane where the axis of the central cylinder 6 is located with the central cylinder as the axis of symmetry, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, the column wall of the central cylinder also has a perforated structure, which is convenient for the transmission of the electrolyte, and the two blades 7 have a perforated structure. The height of the two blades 7 is the same as the height of the central cylinder 6, and the thickness of the blade 7 is 6 μm and the width is 8 mm. Figure 3 It is a top view of the positive electrode current collector 1 used in Example 1. As can be seen from the figure, the positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0075] The cylindrical battery provided in this embodiment is prepared by the following steps: The positive electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the positive active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and the mixture is mixed after being weighed, and after being evenly mixed, the mixture is divided into three positive electrode primary mixtures, and 1% of the mass percentage of the pore-forming agent LiFSI is added to the first positive electrode primary mixture, 1.5% of the mass percentage of the pore-forming agent LiFSI is added to the second positive electrode primary mixture, and 2% of the mass percentage of the pore-forming agent LiFSI is added to the third positive electrode primary mixture, and then the mixture is mixed and fiberized to obtain three evenly dispersed positive electrode mixtures; The negative electrode active material, the binder and the conductive agent are weighed according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and the weighed materials are mixed, and after being evenly mixed, they are divided into three negative electrode primary mixtures, and 1% of the mass percentage of the pore-forming agent LiFSI is added to the first negative electrode primary mixture, 1.5% of the mass percentage of the pore-forming agent LiFSI is added to the second negative electrode primary mixture, and 2% of the mass percentage of the pore-forming agent LiFSI is added to the third negative electrode primary mixture, and then the three negative electrode mixtures are mixed and fiberized to obtain three evenly dispersed negative electrode mixtures; The negative electrode mixture with the lowest pore former content obtained in step (2) is pressed onto the inner wall of a cylindrical metal shell, and then the negative electrode mixture with a medium pore former content is pressed onto the negative electrode mixture with the lowest pore former content, and finally the negative electrode mixture with the highest pore former content is pressed onto the negative electrode mixture with the medium pore former content, to obtain a negative electrode group; The positive electrode mixture with the lowest pore former content prepared in step (1) is first pressed into the positive electrode current collector, and then the positive electrode mixture with a medium pore former content is pressed onto the positive electrode mixture with the lowest pore former content, and finally the positive electrode mixture with the highest pore former content is pressed onto the positive electrode mixture with the medium pore former content, to obtain a positive electrode group; An insulating gasket is placed at the bottom of the inner space of the cylindrical metal shell of the negative electrode group obtained in step (3), and the positive electrode group obtained in step (4) is covered with a separator and placed in the inner space of the cylindrical metal shell, with the central cylinder of the positive electrode collector on the central axis of the cylindrical metal shell, and the tabs on the positive electrode collector blades are welded to the cap of the cylindrical battery to obtain a cylindrical battery preform; The cylindrical battery preform obtained in step (5) is dried, injected, covered, pressed, left to stand, formed, divided and screened to obtain a cylindrical battery.

[0076] Example 2

[0077] This embodiment provides a cylindrical battery. Figure 4 The schematic diagram of the structure of the cylindrical battery provided in Example 2 shows that the cylindrical battery includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, the cross-section of the positive electrode current collector 1 is cross-shaped, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0078] Figure 5 Schematic diagram of the structure of the positive electrode collector used in Example 1. It can be seen from the figure that the positive electrode collector 1 is composed of a central cylinder 6 and four blades 7 coaxially connected to the side of the central cylinder 6. The four blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, the central cylinder also has a perforated structure to facilitate the transmission of the electrolyte, and the four blades 7 have a perforated structure. The height of the four blades 7 is the same as the height of the central cylinder 6, and the thickness of the blade 7 is 6μm and the width is 8mm. Figure 6 This is a top view of the positive electrode current collector 1 used in Example 2. As can be seen from the figure, the positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0079] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0080] Example 3

[0081] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the negative electrode current collector.

[0082] The positive electrode current collector 1 is composed of a central cylinder 6 and six blades 7 coaxially connected to the side of the central cylinder 6. The six blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, and the column wall of the central cylinder also has a perforated structure to facilitate the transmission of the electrolyte. The six blades 7 all have a perforated structure, the height of the six blades 7 is the same as the height of the central cylinder 6, the thickness of the blade 7 is 6 μm, and the width is 8 mm. The positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0083] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0084] Example 4

[0085] The present embodiment provides a cylindrical battery. As can be seen from the figure, the cylindrical battery includes, from the inside to the outside, a positive electrode collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode collector, and the material of the positive electrode collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0086] The positive electrode current collector 1 is composed of a central cylinder 6 and eight blades 7 coaxially connected to the side of the central cylinder 6. The eight blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, and the central cylinder also has a perforated structure to facilitate the transmission of the electrolyte. The eight blades 7 have a perforated structure, and the height of the eight blades 7 is the same as the height of the central cylinder 6. The thickness of the blade 7 is 6μm and the width is 8 mm. The positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0087] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0088] Example 5

[0089] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0090] The positive electrode current collector 1 is composed of a central cylinder 6 and six blades 7 coaxially connected to the side of the central cylinder 6. The six blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, the central cylinder also has a perforated structure, and the six blades 7 have no perforated structure. The height of the six blades 7 is the same as the height of the central cylinder 6, and the thickness of the blade 7 is 6 μm and the width is 8 mm. The positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0091] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0092] Example 6

[0093] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0094] The positive electrode current collector 1 is composed of a central cylinder 6 and six blades 7 coaxially connected to the side of the central cylinder 6. The six blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis, and are on the same plane as the central cylinder 6, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a hollow structure, the outer diameter of the central cylinder 6 is 2 mm, the inner diameter is 1.8 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, the central cylinder does not have a perforated structure, and the six blades 7 have a perforated structure, the height of the six blades 7 is the same as the height of the central cylinder 6, the thickness of the blade 7 is 6 μm, and the width is 8 mm. The positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0095] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0096] Example 7

[0097] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, and the material of the positive electrode current collector 1 is aluminum foil; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5.

[0098] The positive electrode current collector 1 is composed of a central cylinder 6 and six blades 7 coaxially connected to the side of the central cylinder 6. The six blades 7 are symmetrically distributed in pairs on a plane where the axis of the central cylinder 6 is located, with the central cylinder as the symmetry axis. The blades 6 symmetrically distributed with each other are on the same plane as the central cylinder 6, and the side of each blade 7 is connected to the side of the central cylinder 6; the central cylinder 6 is a solid structure, the outer diameter of the central cylinder 6 is 2 mm, the height of the central cylinder 6 is 15 mm less than the height of the cylindrical metal shell 5, the central cylinder does not have a perforated structure, and the six blades 7 have a perforated structure, the height of the six blades 7 is the same as the height of the central cylinder 6, the thickness of the blade 7 is 6 μm, and the width is 8 mm. The positive electrode tab 8 is connected to a blade 7 of the positive electrode current collector 1, and the material of the positive electrode tab 8 is aluminum.

[0099] In the preparation method of the cylindrical battery provided in this embodiment, except for the positive electrode current collector used, everything else is the same as that of Embodiment 1.

[0100] Example 8

[0101] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode collector, the positive electrode active layer 2 contains two positive electrode functional active layers, and the porosity of the two positive electrode active layers 2 gradually increases in the direction away from the positive electrode collector 1; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5; the structure of the positive electrode collector 1 is the same as that in Example 3.

[0102] The cylindrical battery provided in this embodiment is prepared by the following steps: (1) Weighing a positive electrode active material, a binder and a conductive agent according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and mixing them after weighing, and then dividing them into two positive electrode primary mixtures after mixing evenly, adding 1% of the mass percentage of pore-forming agent LiFSI to the first positive electrode primary mixture, and adding 2% of the mass percentage of the pore-forming agent LiFSI to the second positive electrode primary mixture, and then mixing and fiberizing them to obtain two evenly dispersed positive electrode mixtures; (2) Weighing the negative electrode active material, the binder and the conductive agent according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and mixing them after weighing, and then dividing them into three negative electrode primary mixtures after mixing evenly, adding 1% by mass of the pore-forming agent LiFSI to the first negative electrode primary mixture, adding 1.5% by mass of the pore-forming agent LiFSI to the second negative electrode primary mixture, and adding 2% by mass of the pore-forming agent LiFSI to the third negative electrode primary mixture, and then mixing and fiberizing them to obtain three evenly dispersed negative electrode mixtures; (3) pressing the negative electrode mixture with the lowest pore former content obtained in step (2) onto the inner wall of a cylindrical metal shell, then pressing the negative electrode mixture with a medium pore former content onto the negative electrode mixture with the lowest pore former content, and finally pressing the negative electrode mixture with the highest pore former content onto the negative electrode mixture with the medium pore former content, to obtain a negative electrode group; (4) first pressing the positive electrode mixture with the lowest pore former content obtained in step (1) into the positive electrode current collector, and then pressing the positive electrode mixture with the highest pore former content onto the positive electrode mixture with the lowest pore former content, to obtain a positive electrode group; (5) placing an insulating gasket at the bottom of the inner space of the cylindrical metal shell of the negative electrode group obtained in step (3), and placing the positive electrode group obtained in step (4) in the inner space of the cylindrical metal shell after being covered with a separator, with the central cylinder of the positive electrode collector on the central axis of the cylindrical metal shell, and then welding the tabs on the positive electrode collector blades to the cap of the cylindrical battery to obtain a cylindrical battery preform; (6) The cylindrical battery preform obtained in step (5) is dried, injected with liquid, covered, pressed into shape, left to stand, formed, divided into different caps and screened to obtain a cylindrical battery.

[0103] Example 9

[0104] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, the positive electrode active layer 2 contains a positive electrode functional active layer, and the positive electrode functional active layer has a certain porosity; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5; the structure of the positive electrode current collector 1 is the same as that in Example 3.

[0105] The cylindrical battery provided in this embodiment is prepared by the following steps: (1) Weighing a positive electrode active material, a binder and a conductive agent according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the fiberized binder is 95.95:1.55:2.5, and mixing them after weighing, and mixing them evenly to obtain a positive electrode primary mixture, adding 1.5% by mass of a pore-forming agent LiFSI to the positive electrode primary mixture, and mixing and fiberizing to obtain a uniformly dispersed positive electrode mixture; (2) Weighing the negative electrode active material, the binder and the conductive agent according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the active material, the conductive agent and the binder is 96:1.5:2.5, and mixing them after weighing, and then dividing them into three negative electrode primary mixtures after mixing evenly, adding 1% of the pore-forming agent LiFSI to the first negative electrode primary mixture, adding 1.5% of the pore-forming agent LiFSI to the second negative electrode primary mixture, and adding 2% of the pore-forming agent LiFSI to the third negative electrode primary mixture, and then mixing and fiberizing them to obtain three evenly dispersed negative electrode mixtures; (3) pressing the negative electrode mixture with the lowest pore former content obtained in step (2) onto the inner wall of a cylindrical metal shell, then pressing the negative electrode mixture with a medium pore former content onto the negative electrode mixture with the lowest pore former content, and finally pressing the negative electrode mixture with the highest pore former content onto the negative electrode mixture with the medium pore former content, to obtain a negative electrode group; (4) pressing the positive electrode mixture prepared in step (1) into a positive electrode current collector to obtain a positive electrode group; (5) placing an insulating gasket at the bottom of the inner space of the cylindrical metal shell of the negative electrode group obtained in step (3), and placing the positive electrode group obtained in step (4) in the inner space of the cylindrical metal shell after being covered with a separator, with the central cylinder of the positive electrode collector on the central axis of the cylindrical metal shell, and then welding the tabs on the positive electrode collector blades to the cap of the cylindrical battery to obtain a cylindrical battery preform; (6) The cylindrical battery preform obtained in step (5) is dried, injected with liquid, covered, pressed into shape, left to stand, formed, divided into different caps and screened to obtain a cylindrical battery.

[0106] Example 10

[0107] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode collector; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode active layers gradually increases in the direction away from the positive electrode collector 1; the negative electrode active layer 4 contains two negative electrode functional active layers, and the porosity of the two negative electrode functional active layers gradually increases in the direction away from the metal shell 5; the structure of the positive electrode collector 1 is the same as that in Example 3.

[0108] The cylindrical battery provided in this embodiment is prepared by the following steps: (1) Weighing a positive electrode active material, a binder and a conductive agent according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and mixing them after weighing, and then dividing them into three positive electrode primary mixtures after mixing evenly, adding 1% by mass of a pore-forming agent LiFSI to the first positive electrode primary mixture, adding 1.5% by mass of a pore-forming agent LiFSI to the second positive electrode primary mixture, and adding 2% by mass of a pore-forming agent LiFSI to the third positive electrode primary mixture, and then mixing and fiberizing them to obtain three evenly dispersed positive electrode mixtures; (2) Weighing the negative electrode active material, the binder and the conductive agent according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the fiberized binder is 96:1.5:2.5, and mixing them after weighing, and then dividing them into two negative electrode primary mixtures after mixing evenly, adding 1.24% of the pore-forming agent LiFSI to the first negative electrode primary mixture, and adding 1.75% of the pore-forming agent LiFSI to the second negative electrode primary mixture, and then mixing and fiberizing them to obtain two evenly dispersed negative electrode mixtures; (3) pressing the negative electrode mixture with the lowest pore-forming agent content obtained in step (2) onto the inner wall of a cylindrical metal shell, and then pressing the negative electrode mixture with the highest pore-forming agent content onto the negative electrode mixture with the lowest pore-forming agent content to obtain a negative electrode group; (4) first pressing the positive electrode mixture with the lowest pore former content prepared in step (1) into the positive electrode current collector, then pressing the positive electrode mixture with a medium pore former content onto the positive electrode mixture with the lowest pore former content, and finally pressing the positive electrode mixture with the highest pore former content onto the positive electrode mixture with a medium pore former content, to obtain a positive electrode group; (5) placing an insulating gasket at the bottom of the inner space of the cylindrical metal shell of the negative electrode group obtained in step (3), and placing the positive electrode group obtained in step (4) in the inner space of the cylindrical metal shell after being covered with a separator, with the central cylinder of the positive electrode collector on the central axis of the cylindrical metal shell, and then welding the tabs on the positive electrode collector blades to the cap of the cylindrical battery to obtain a cylindrical battery preform; (6) The cylindrical battery preform obtained in step (5) is dried, injected with liquid, covered, pressed into shape, left to stand, formed, divided into different caps and screened to obtain a cylindrical battery.

[0109] Embodiment 11

[0110] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode collector; the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode active layers gradually increases in the direction away from the positive electrode collector 1; the negative electrode active layer 4 contains a negative electrode functional active layer, and the negative electrode active layer 4 has a certain porosity; the structure of the positive electrode collector 1 is the same as that in Example 3.

[0111] The cylindrical battery provided in this embodiment is prepared by the following steps: (1) Weighing a positive electrode active material, a binder and a conductive agent according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and mixing them after weighing, and then dividing them into three positive electrode primary mixtures after mixing evenly, adding 1% by mass of a pore-forming agent LiFSI to the first positive electrode primary mixture, adding 1.5% by mass of a pore-forming agent LiFSI to the second positive electrode primary mixture, and adding 2% by mass of a pore-forming agent LiFSI to the third positive electrode primary mixture, and then mixing and fiberizing them to obtain three evenly dispersed positive electrode mixtures; (2) Weighing the negative electrode active material, the binder and the conductive agent according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and mixing them after weighing, and mixing them evenly to obtain a negative electrode primary mixture, adding 1.5% by mass of a pore-forming agent LiFSI to the negative electrode primary mixture, and mixing and fiberizing to obtain a uniformly dispersed negative electrode mixture; (3) pressing the negative electrode mixture obtained in step (2) onto the inner wall of a cylindrical metal shell to obtain a negative electrode group; (4) first pressing the positive electrode mixture with the lowest pore former content prepared in step (1) into the positive electrode current collector, then pressing the positive electrode mixture with a medium pore former content onto the positive electrode mixture with the lowest pore former content, and finally pressing the positive electrode mixture with the highest pore former content onto the positive electrode mixture with a medium pore former content, to obtain a positive electrode group; (5) placing an insulating gasket at the bottom of the inner space of the cylindrical metal shell of the negative electrode group obtained in step (3), and placing the positive electrode group obtained in step (4) in the inner space of the cylindrical metal shell after being covered with a separator, with the central cylinder of the positive electrode collector on the central axis of the cylindrical metal shell, and then welding the tabs on the positive electrode collector blades to the cap of the cylindrical battery to obtain a cylindrical battery preform; (6) The cylindrical battery preform obtained in step (5) is dried, injected with liquid, covered, pressed into shape, left to stand, formed, divided into different caps and screened to obtain a cylindrical battery.

[0112] Example 12

[0113] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector, the positive electrode active layer 2 contains three positive electrode functional active layers, and the porosity of the three positive electrode functional active layers gradually increases in the direction away from the positive electrode current collector 1; the negative electrode active layer 4 contains a negative electrode functional active layer, and the negative electrode functional active layer has a certain porosity; the structure of the positive electrode current collector 1 is the same as that in Example 3.

[0114] The method for preparing the cylindrical battery in this embodiment is different from that in Embodiment 11 in that the negative electrode mixture prepared in step (2) does not contain a pore-forming agent, and the rest is the same as that in Embodiment 11.

[0115] Embodiment 13

[0116] The present embodiment provides a cylindrical battery, which includes, from the inside to the outside, a positive electrode current collector 1, a positive electrode active layer 2, a separator 3, a negative electrode active layer 4 and a cylindrical metal shell 5, wherein the cylindrical metal shell 5 serves as a negative electrode current collector; the positive electrode active layer 2 contains a positive electrode functional active layer, and the positive electrode functional active layer has a certain porosity; the negative electrode active layer 4 contains three negative electrode functional active layers, and the porosity of the three negative electrode functional active layers gradually increases in the direction away from the metal shell 5; the structure of the positive electrode current collector 1 is the same as that in Example 3.

[0117] The method for preparing the cylindrical battery in this embodiment is different from that in Embodiment 9 in that the positive electrode mixture in step (1) does not contain a pore former, and the rest is the same as that in Embodiment 9.

[0118] Comparative Example 1 This comparative example provides a cylindrical battery, which has a conventional structure. The positive electrode sheet is a positive electrode film made by a dry process pressed onto an aluminum foil, and the negative electrode sheet is a negative electrode film made by a dry process pressed onto a copper foil. The positive and negative electrode sheet separation films are wound into a winding core using a winding process, and the positive and negative electrodes of the core are respectively welded to the positive electrode cap and the negative electrode shell of the cylinder.

[0119] The cylindrical battery provided in this comparative example is prepared by the following steps: The positive electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and the weighed materials are mixed, and after being evenly mixed, they are divided into three positive electrode primary mixtures, and 1% of the mass percentage of the pore-forming agent LiFSI is added to the first positive electrode primary mixture, 1.5% of the mass percentage of the pore-forming agent LiFSI is added to the second positive electrode primary mixture, and 2% of the mass percentage of the pore-forming agent LiFSI is added to the third positive electrode primary mixture, and then the three positive electrode mixtures are mixed and fiberized to obtain three evenly dispersed positive electrode mixtures; The negative electrode active material, the binder and the conductive agent are weighed according to the ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and the weighed materials are mixed, and after being evenly mixed, they are divided into three negative electrode primary mixtures, and 1% of the mass percentage of the pore-forming agent LiFSI is added to the first negative electrode primary mixture, 1.5% of the mass percentage of the pore-forming agent LiFSI is added to the second negative electrode primary mixture, and 2% of the mass percentage of the pore-forming agent LiFSI is added to the third negative electrode primary mixture, and then the three negative electrode mixtures are mixed and fiberized to obtain three evenly dispersed negative electrode mixtures; The negative electrode mixture with the lowest pore former content obtained in step (2) is pressed onto a copper foil, and then the negative electrode mixture with a medium pore former content is pressed onto the negative electrode mixture with the lowest pore former content, and finally the negative electrode mixture with the highest pore former content is pressed onto the negative electrode mixture with the medium pore former content, and the negative electrode materials are pressed on the other side of the copper foil in a similar manner, and finally a negative electrode group is obtained; The positive electrode mixture with the lowest pore-forming agent content obtained in step (1) is first pressed onto an aluminum foil, and then the positive electrode mixture with a medium pore-forming agent content is pressed onto the positive electrode mixture with the lowest pore-forming agent content, and finally the positive electrode mixture with the highest pore-forming agent content is pressed onto the positive electrode mixture with the medium pore-forming agent content, and the positive electrode materials are pressed on the other side of the aluminum foil in a similar manner to obtain a positive electrode group; The positive and negative electrode sheets and the separator prepared in step (4) are wound to obtain a cylindrical winding core, the negative electrode tab of the winding core is welded to the bottom shell of the cylinder, and the positive electrode tab is welded to the cap to obtain a cylindrical battery preform; The cylindrical battery preform obtained in step (5) is dried, injected, covered, pressed, left to stand, formed, divided and screened to obtain a cylindrical battery.

[0120] Comparative Example 2 This comparative example provides a cylindrical battery, which has a conventional structure. The positive electrode sheet is a positive electrode film made by a dry process pressed onto an aluminum foil, and the negative electrode sheet is a negative electrode film made by a dry process pressed onto a copper foil. The positive and negative electrode sheet separation films are wound into a winding core using a winding process, and the positive and negative electrodes of the core are respectively welded to the positive electrode cap and the negative electrode shell of the cylinder.

[0121] The cylindrical battery provided in this comparative example is prepared by the following steps: The positive electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the positive electrode active material, the conductive agent and the binder is 95.95:1.55:2.5, and the weighed materials are mixed to obtain a positive electrode primary mixture after uniform mixing, and a pore-forming agent LiFSI accounting for 1.5% by mass is added to the positive electrode primary mixture, and then the mixture is mixed and fiberized to obtain a uniformly dispersed positive electrode mixture; The negative electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and the mixture is weighed and mixed, and a negative electrode primary mixture is obtained after uniform mixing, and a pore-forming agent LiFSI accounting for 1.5% by mass is added to the negative electrode primary mixture, and then the mixture is mixed and fiberized to obtain a uniformly dispersed negative electrode mixture; Pressing the negative electrode mixture obtained in step (2) onto both sides of the copper foil to obtain a negative electrode group; Pressing the positive electrode mixture prepared in step (1) onto both sides of an aluminum foil to obtain a positive electrode group; The positive and negative electrode sheets and the separator prepared in step (4) are wound to obtain a cylindrical winding core, the negative electrode tab of the winding core is welded to the bottom shell of the cylinder, and the positive electrode tab is welded to the cap to obtain a cylindrical battery preform; The cylindrical battery preform obtained in step (5) is dried, injected, covered, pressed, left to stand, formed, divided and screened to obtain a cylindrical battery.

[0122] Comparative Example 3 This comparative example provides a cylindrical battery, which has a conventional structure. The positive electrode sheet is a positive electrode film made by a dry process pressed onto an aluminum foil, and the negative electrode sheet is a negative electrode film made by a dry process pressed onto a copper foil. The positive and negative electrode sheet separation films are wound into a winding core using a winding process, and the positive and negative electrodes of the core are respectively welded to the positive electrode cap and the negative electrode shell of the cylinder.

[0123] The cylindrical battery provided in this embodiment is prepared by the following steps: The positive electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the positive electrode active material is a ternary positive electrode material, the conductive agent includes single-walled carbon nanotubes and conductive carbon black, and the binder is a fiberized binder; the mass ratio of the active material, the conductive agent and the binder is 95.95:1.55:2.5, and the weighed materials are mixed to obtain a uniformly dispersed positive electrode mixture through mixing and fiberization; The negative electrode active material, the binder and the conductive agent are weighed according to a ratio, wherein the negative electrode active material is graphite, the conductive agent is conductive carbon black, and the binder is a fiberized binder; the mass ratio of the negative electrode active material, the conductive agent and the binder is 96:1.5:2.5, and the weighed materials are mixed to obtain a uniformly dispersed negative electrode mixture through mixing and fiberization; (3) pressing the negative electrode mixture obtained in step (2) onto both sides of a copper foil to obtain a negative electrode assembly; (4) Pressing the positive electrode mixture prepared in step (1) onto both sides of an aluminum foil to obtain a positive electrode assembly; (5) Winding the positive and negative electrode sheets and the separator obtained in step (4) to obtain a cylindrical winding core, welding the negative electrode tab of the winding core to the bottom shell of the cylinder, and welding the positive electrode tab to the cap to obtain a cylindrical battery preform; (6) The cylindrical battery preform obtained in step (5) is dried, injected with liquid, covered, pressed into shape, left to stand, formed, divided into different caps and screened to obtain a cylindrical battery.

[0124] The cylindrical batteries in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 1: Porosity test Soak the positive or negative electrode in DMC solvent at room temperature for 3 times, each time for 10 min, and use fresh DMC solvent each time; place the soaked positive or negative electrode in a vacuum drying oven for 3 h to wait for DMC to completely evaporate; place the positive or negative electrode to be tested in a mercury intrusion instrument, and test the porosity according to the operating procedures to finally obtain the porosity of the electrode.

[0125] Rate capacity ratio test Qualified batteries were selected for rate testing. The charging was uniformly a 1 C constant current and constant voltage test with a cut-off voltage of 4.25 V and a cut-off current of 0.05 C. The batteries were discharged at rates of 0.2 C, 0.5 C, 1 C, and 2 C, with a discharge cut-off voltage of 2.8 V. The discharge capacities at different rates were obtained, and the rate performance was finally derived using the 2 C discharge capacity / 0.2 C discharge capacity.

[0126] Capacity retention test Qualified batteries were selected for cycle testing and tested in a charge and discharge box at 45 ℃. The battery was kept warm for 1 h before charging and discharging. The cycle test step was 1 C constant current and constant voltage test. The cut-off voltage was 4.25 V, the cut-off current was 0.05C, and the battery was left for 5 min in the middle. After discharging at 1 C to 2.8 V, the battery was left for 5 min. The above charge and discharge was recorded as 1 cycle. After the battery had been cycled for 1000 weeks, the capacity of the battery was recorded, and the capacity retention rate was calculated as the capacity at the 1000th week / the capacity at the first week.

[0127]

[0128] From the data in Table 1, it can be seen that when the number of positive electrode current collector leaves increases from 2 to 6, the rate, capacity and cycle of the battery are significantly improved. However, when it increases to 8 pieces, the rate is slightly improved, but the capacity is reduced. The reason may be that the extra aluminum pieces lead to a decrease in active materials, which ultimately leads to a decrease in energy density. Overall, the performance of 6 aluminum current collectors is the best.

[0129] Compared with conventional cylindrical batteries, batteries with optimized current collectors have significantly higher capacity, reduced the amount of foil, and increased active materials. Using three layers of positive and negative electrodes with pore gradients can significantly improve the battery's rate, capacity, and cycle.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cylindrical battery, characterized in that: The dry positive electrode group includes a dry positive electrode group, a separator and a dry negative electrode group from the inside to the outside; the dry positive electrode group includes a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector; the dry negative electrode group includes a negative electrode current collector and a negative electrode active layer arranged on at least one surface of the negative electrode current collector; The positive electrode current collector has a central cylinder and a plurality of blades coaxially connected to the side of the central cylinder, the plurality of blades are respectively located on planes passing through the axis of the central cylinder, the central cylinder is arranged along the axial direction of the cylindrical battery, and the plurality of blades are arranged at intervals from each other; the negative electrode current collector is the metal shell of the cylindrical battery.

2. The cylindrical battery according to claim 1, characterized in that: The plurality of blades are symmetrically arranged in pairs with the central cylinder as the symmetry axis; And / or, positive electrode active layers are disposed on both surfaces of the plurality of blades.

3. The cylindrical battery according to claim 1, characterized in that: The number of the blades is more than 2; And / or, the blade is rectangular or square in shape; And / or, the blade has a hollow structure.

4. The cylindrical battery according to claim 3, characterized in that: The number of the blades is 4, 6, 8 or 10; and / or, the height of the blades is the same as the height of the central cylinder; and / or, the thickness of the blade is 3-9 μm; And / or, the width of the blade is 1 / 2-2 / 3 of the inner diameter of the cylindrical battery.

5. The cylindrical battery according to claim 1, characterized in that: The central cylinder has a hollow structure, and the cylinder wall of the central cylinder has a hollow structure.

6. The cylindrical battery according to claim 1, characterized in that: The inner diameter of the central cylinder is 0-3 mm and the outer diameter is 0.5-3.2 mm; and / or, the height of the central cylinder is 15-30 mm lower than the height of the metal shell; And / or, a positive electrode active layer is arranged on the outer surface of the central cylinder.

7. The cylindrical battery according to claim 1, characterized in that: The positive electrode active layer has N positive electrode functional active layers, N≥1; the negative electrode active layer has N negative electrode functional active layers, N≥1; And / or, the material of the positive electrode current collector is aluminum foil or copper foil.

8. The cylindrical battery according to claim 7, characterized in that: The N positive electrode functional active layers have a gradient porosity, and the porosity gradually increases along the direction from the positive electrode current collector to the surface of the positive electrode active layer; And / or, the N negative electrode functional active layers have a gradient porosity, and the porosity gradually increases along the direction from the negative electrode current collector to the surface of the negative electrode active layer.

9. A method for preparing a cylindrical battery according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. The raw materials of the positive electrode active layer are mixed and fiberized to obtain a positive electrode mixture; the raw materials of the negative electrode active layer are mixed and fiberized to obtain a negative electrode mixture; S2, pressing the negative electrode mixture described in step S1 onto the metal shell of the cylindrical battery to obtain a negative electrode group; pressing the positive electrode mixture described in step S1 into a positive electrode collector to obtain a positive electrode group; the positive electrode collector has a central cylinder and a plurality of blades coaxially connected to the side of the central cylinder, and the plurality of blades are spaced apart from each other; S3, putting a separator on the positive electrode assembly of step S2 and assembling it with the negative electrode, so that the central cylinder of the positive electrode collector is arranged along the axial direction of the cylindrical battery, and then drying, injecting liquid, closing the cover, pressing and forming, standing, forming, dividing the capacity and screening to obtain a cylindrical battery.

10. The method for preparing a cylindrical battery according to claim 9, characterized in that: Step S1: the raw materials of the positive electrode active layer include positive electrode active material, binder, conductive agent and pore-forming agent; The raw materials of the negative electrode active layer in step S1 include negative electrode active material, binder, conductive agent and pore former.

11. The method for preparing a cylindrical battery according to claim 10, characterized in that: In step S1, the positive electrode active material, the binder and the conductive agent are first mixed evenly, and then the pore former is added and mixed evenly to obtain the positive electrode mixture; In step S1, the negative electrode active material, the binder and the conductive agent are firstly mixed evenly, and then the pore former is added and mixed evenly to obtain the negative electrode mixture.

12. The method for preparing a cylindrical battery according to claim 10, characterized in that: The positive electrode mixture is divided into N parts, the N parts of the positive electrode mixture have different contents of pore formers, and the N parts of the positive electrode mixture are pressed on the positive electrode current collector in order of the content of the pore former from low to high; And / or, the negative electrode mixture is divided into N parts, the N parts of the negative electrode mixture have different contents of the pore former, and the N parts of the negative electrode mixture are pressed on the negative electrode current collector in order of the content of the pore former from low to high; And / or, the pore former includes at least one of LiFSI, LiTFSI and LiPO2F2.

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