Cylindrical secondary battery and electronic device

Abstract

The invention provides a cylindrical secondary battery and an electronic device, the cylindrical secondary battery comprises an electrode assembly, the electrode assembly comprises a negative electrode plate, the negative electrode plate comprises a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector, based on the volume of the electrode assembly, the volume ratio of the negative electrode current collector is D%, the volume ratio of the negative electrode material layer is C%, and 3 < = 3D-0.2 C < = 12. Through the arrangement, the mechanical safety performance of the cylindrical secondary battery can be improved under the condition of considering the energy density of the cylindrical secondary battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, and particularly relates to a cylindrical secondary battery and an electronic device. BACKGROUND

[0002] The cylindrical secondary battery, such as the cylindrical lithium ion battery, has the characteristics of high specific energy, high working voltage, low self-discharge rate, small volume, light weight and the like. With the wide application of the cylindrical secondary battery in the consumer electronics field, the market puts forward higher and higher requirements for the mechanical safety performance of the cylindrical secondary battery.

[0003] In the prior art, the method of thickening the battery shell is usually adopted to improve the structural rigidity of the cylindrical secondary battery and improve the mechanical safety performance of the cylindrical secondary battery. However, thickening the shell of the secondary battery will result in the reduction of the energy density of the cylindrical secondary battery. SUMMARY

[0004] The present application aims to provide a cylindrical secondary battery and an electronic device, which improve the mechanical safety performance of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery. The specific technical solutions are as follows.

[0005] The first aspect of the present application provides a cylindrical secondary battery, comprising an electrode assembly, the electrode assembly comprising a negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector, the volume proportion of the negative electrode current collector being D% and the volume proportion of the negative electrode material layer being C% based on the volume of the electrode assembly, and -3≤3D-0.2C≤12, preferably 3≤3D-0.2C≤10, and more preferably 5≤3D-0.2C≤9. In the present application, the numerical range of 3D-0.2C is controlled within the above range, and then the volume proportion ratio between the negative electrode current collector and the negative electrode material layer in the negative electrode sheet of the electrode assembly is controlled. The negative electrode current collector and the negative electrode material layer are arranged in combination, the electrode assembly can have a higher bearing capacity to offset the impact force during mechanical impact, the deformation of the electrode assembly is reduced, the cylindrical secondary battery has a better pass rate in the impact test of the finished battery, the mechanical strength of the electrode assembly can be improved while taking into account the energy density of the cylindrical secondary battery, the electrode assembly has better rigidity, and the mechanical safety performance of the cylindrical secondary battery is improved.

[0006] In one or more embodiments, 2≤D≤6, preferably 3≤D≤5, and 30≤C≤45, preferably 35≤C≤40. In the present application, the volume proportion D of the negative electrode current collector and the volume proportion C of the negative electrode material layer in the negative electrode sheet of the electrode assembly are controlled within the above range, which is beneficial to improve the mechanical strength of the electrode assembly while taking into account the energy density of the cylindrical secondary battery, so that the electrode assembly has better rigidity, and the mechanical safety performance of the cylindrical secondary battery is improved.

[0007] In one or more embodiments, the coating weight per unit area of ​​the negative electrode material layer is Amg / 1540mm 2 , 100≤A≤250. By regulating the coating weight per unit area of ​​the negative electrode material layer within the above range, the mechanical safety performance of the cylindrical secondary battery is improved while taking into account the energy density of the cylindrical secondary battery.

[0008] In one or more embodiments, the thickness of the negative electrode sheet is B μm, and 0.5 ≤ B / A ≤ 1.5, preferably 0.8 ≤ B / A ≤ 1.2. By adjusting B / A within the above range, the thickness of the negative electrode sheet and the coating weight per unit area are adjusted to improve the mechanical safety performance of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery.

[0009] In one or more embodiments, the thickness of the negative electrode current collector is E μm, 5 ≤ E ≤ 15, preferably, 8 ≤ E ≤ 12. By regulating the thickness of the negative electrode current collector within the above range, the hardness of the negative electrode current collector is greater, which is conducive to improving the support strength of the negative electrode current collector on the electrode assembly, thereby improving the mechanical strength of the electrode assembly, and improving the mechanical safety performance of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery.

[0010] In one or more embodiments, the negative electrode material layer includes a negative electrode active material, which includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-oxygen, or a silicon-carbon composite. The weight percentage of the negative electrode active material is 95.0% to 98.0% based on the weight of the negative electrode material layer. By selecting the above-mentioned negative electrode active materials, the secondary battery has a high energy density while also taking into account the structural stability of the negative electrode sheet.

[0011] In one or more embodiments, the electrode assembly includes a positive electrode sheet. Based on the volume of the electrode assembly, the ratio of the volume share of the negative electrode sheet to the volume share of the positive electrode sheet is F, 0.5≤F≤1.2, preferably, 0.8≤F≤1.2. By regulating the ratio of the volume share of the negative electrode sheet to the volume share of the positive electrode sheet within the above range, the ratio of the positive electrode sheet to the negative electrode sheet is within an appropriate range, while improving the mechanical safety performance of the electrode assembly and taking into account the energy density of the cylindrical secondary battery.

[0012] In one or more embodiments, the thickness of the positive electrode sheet is G μm, 150 ≤ G ≤ 350. By controlling the thickness of the positive electrode sheet within the above range, it is beneficial to improve the support strength of the positive electrode sheet to the electrode assembly, improve the mechanical safety performance of the cylindrical secondary battery, and take into account the energy density of the cylindrical secondary battery.

[0013] In one or more embodiments, the positive electrode sheet includes a positive electrode current collector having a thickness of H μm, where 8 ≤ H ≤ 15. By controlling the thickness of the positive electrode current collector in the positive electrode sheet within the above range, the support strength of the positive electrode current collector for the electrode assembly is improved, reducing the risk of a decrease in the energy density of the cylindrical secondary battery due to excessive thickness of the positive electrode current collector. While maintaining the energy density of the cylindrical secondary battery, the mechanical safety performance of the cylindrical secondary battery is improved.

[0014] A second aspect of the present application provides an electronic device comprising a cylindrical secondary battery according to any of the aforementioned embodiments. The cylindrical secondary battery of the present application has good mechanical safety performance after cycling while taking into account the secondary battery energy density. Therefore, the electronic device of the present application has a long service life.

[0015] Beneficial effects of the embodiments of the present application:

[0016] The embodiment of the present application adjusts the numerical range of 3D-0.2C within the above range, thereby adjusting the volume ratio between the negative electrode current collector and the negative electrode material layer of the negative electrode sheet in the electrode assembly. The negative electrode current collector and the negative electrode material layer are arranged in a coordinated manner, and the electrode assembly can have a higher bearing capacity to offset the impact force during mechanical impact, thereby reducing the deformation of the electrode assembly, so that the secondary battery has a better pass rate in the impact test of the finished battery, and can improve the mechanical strength of the electrode assembly while taking into account the energy density of the cylindrical secondary battery, so that the electrode assembly has better rigidity, thereby improving the mechanical safety performance of the cylindrical secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0018] Figure 1 This is a schematic diagram of the structure of a cylindrical secondary battery after impact testing in the prior art;

[0019] Figure 2 A schematic diagram of the winding structure of an electrode assembly in one embodiment of the present application;

[0020] Figure 3 This is a schematic diagram of the structure of a cylindrical secondary battery after impact testing in one embodiment of the present application.

[0021] Reference numerals: electrode assembly 100 ; separator 30 ; positive electrode sheet 10 ; positive electrode current collector 11 ; positive electrode material layer 12 ; negative electrode sheet 20 ; negative electrode current collector 21 ; negative electrode material layer 22 ; secondary battery 200 . DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It is apparent that the described examples are only a portion of the embodiments of this application, rather than all of them. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0023] During the use of cylindrical secondary batteries, they are likely to encounter mechanical shocks such as collisions and hammering. Figure 1 As shown, the cylindrical secondary battery 200 in the prior art will undergo a large deformation after being impacted by a heavy force N during an impact test. At this time, the electrode assembly in the cylindrical secondary battery will be subjected to high pressure extrusion and friction, which may cause the pole pieces in the electrode assembly to break and dislocate, resulting in pole piece and current collector debris. The breakage, dislocation and debris of the pole pieces may cause the cylindrical secondary battery to short-circuit, increasing the safety risk of fire and explosion of the secondary battery. In the prior art, the method of increasing the thickness of the secondary battery shell is usually adopted to improve the structural rigidity of the cylindrical secondary battery, thereby improving the mechanical safety performance of the cylindrical secondary battery. However, under the same secondary battery specifications, the increase in the thickness of the secondary battery shell will lead to a decrease in the energy density of the cylindrical secondary battery. Therefore, the present application provides a cylindrical secondary battery, which is beneficial to improving the mechanical safety performance of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery.

[0024] It should be noted that in the specific embodiments of this application, lithium-ion batteries are used as an example of secondary batteries to explain this application, but the secondary batteries of this application are not limited to lithium-ion batteries. The specific technical solutions are as follows:

[0025] A first aspect of the present application provides a cylindrical secondary battery, comprising an electrode assembly, the electrode assembly comprising a negative electrode pole piece, the negative electrode pole piece comprising a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector, wherein based on the volume of the electrode assembly, the volume proportion of the negative electrode current collector is D%, the volume proportion of the negative electrode material layer is C%, -3≤3D-0.2C≤12, preferably, 3≤3D-0.2C≤10, preferably, 5≤3D-0.2C≤9, for example, the value of 3D-0.2C can be -3, -2.6, -2.3, -2, -1.6, -1.3, -1, 0, 1, 2, 3, 3.3, 3.5, 3.7, 4, 5, 5.3, 5.5, 5.7, 6, 7, 8, 8.3, 8.5, 8.7, 9, 10, 11, 12 or a range consisting of any two of these values.

[0026] For example, Figure 2As shown, the electrode assembly 100 is formed by stacking and winding a separator 30, a positive electrode sheet 10, a separator 30, and a negative electrode sheet 20. The positive electrode sheet 10 includes a positive electrode current collector 11 and a positive electrode material layer 12 disposed on both surfaces of the positive electrode current collector 11. The negative electrode sheet 20 includes a negative electrode current collector 21 and a negative electrode material layer 22 disposed on both surfaces of the negative electrode current collector 21.

[0027] If the value of 3D-0.2C is too small, that is, less than the lower limit of this application, the volume proportion of the negative electrode current collector is too small relative to the volume proportion of the negative electrode material layer, resulting in a decrease in the strength of the electrode assembly and a decrease in the mechanical safety performance of the secondary battery; if the value of 3D-0.2C is too large, that is, greater than the upper limit of this application, the volume proportion of the negative electrode current collector is too large relative to the volume proportion of the negative electrode material layer. Due to the excessive volume proportion of the negative electrode current collector, the energy density of the secondary battery is greatly reduced.

[0028] like Figure 3 As shown, the secondary battery 200 of the present application undergoes minimal deformation after being impacted by a heavy object force N during an impact test. By regulating the numerical range of 3D-0.2C within the aforementioned range, the volume ratio between the negative electrode current collector and the negative electrode material layer of the negative electrode sheet in the electrode assembly is regulated. The arrangement between the negative electrode current collector and the negative electrode material layer allows the electrode assembly to have a higher bearing capacity, thereby offsetting the impact force during mechanical impact, reducing deformation of the electrode assembly, and enabling the secondary battery to have a better pass rate in the impact test of the finished battery. This improves the mechanical strength of the electrode assembly while taking into account the energy density of the cylindrical secondary battery, resulting in a better rigidity of the electrode assembly and thus improving the mechanical safety performance of the cylindrical secondary battery.

[0029] In one or more embodiments, 2≤D≤6, preferably, 3≤D≤5. For example, the value of D can be 2, 2.3, 2.5, 2.7, 3, 4, 5, 5.3, 5.5, 5.7, 6, or a range consisting of any two of these values. 30≤C≤45, preferably, 35≤C≤40. For example, the value of C can be 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or a range consisting of any two of these values. By regulating the volume proportion D of the negative electrode current collector of the negative electrode sheet in the electrode assembly and the volume proportion C of the negative electrode material layer within the above range, it is beneficial to take into account the energy density of the cylindrical secondary battery while improving the mechanical strength of the electrode assembly, so that the electrode assembly has good rigidity, thereby improving the mechanical safety performance of the cylindrical secondary battery.

[0030] In one or more embodiments, the coating weight per unit area of ​​the negative electrode material layer is A mg / 1540 mm 2, 100≤A≤250. For example, the value of A can be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, or a range consisting of any two of these values. By regulating the coating weight per unit area of ​​the negative electrode material layer within the above range, the risk of excessive negative electrode active material in the negative electrode material layer causing a decrease in the rigidity of the electrode assembly is reduced, while the risk of insufficient negative electrode active material in the negative electrode material layer causing a low energy density of the secondary battery is reduced. This improves the mechanical safety of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery.

[0031] In one or more embodiments, the thickness of the negative electrode sheet is B μm, 0.5 ≤ B / A ≤ 1.5, preferably, 0.8 ≤ B / A ≤ 1.2. For example, the value of B / A can be 0.5, 0.6, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, or a range consisting of any two of these values. By regulating B / A within the above range, the thickness of the negative electrode sheet is matched with the coating weight per unit area. This reduces the risk of excessive negative active material in the negative electrode sheet causing a decrease in the rigidity of the electrode assembly, while also reducing the risk of insufficient negative active material in the negative electrode sheet causing a lower energy density of the secondary battery. This improves the mechanical safety of the cylindrical secondary battery while taking into account the energy density of the cylindrical secondary battery.

[0032] In one or more embodiments, the thickness of the negative electrode current collector is Eμm, 5≤E≤15, preferably, 8≤E≤12. For example, the value of E can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or a range consisting of any two values ​​therein. By regulating the thickness of the negative electrode current collector within the above range, the hardness of the negative electrode current collector is relatively large, which is beneficial to improving the supporting strength of the negative electrode current collector to the electrode assembly, thereby improving the mechanical strength of the electrode assembly, while taking into account the energy density of the cylindrical secondary battery, and improving the mechanical safety performance of the cylindrical secondary battery. The present application does not limit the regulation method of the negative electrode current collector. For example, commercially available current collectors of different thicknesses can be selected, and the thickness of the negative electrode current collector can be determined in combination with the test method of "D, C, B, E, F, G, H test" in this application, and then the negative electrode current collector of the required thickness can be selected.

[0033] In one or more embodiments, the negative material layer comprises a negative active material, the negative active material comprises at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-oxygen or silicon-carbon composite, the mass percentage of the negative active material is 95.0% to 98.0% based on the mass of the negative material layer, for example, the mass percentage of the negative active material can be 95.0%, 95.3%, 95.6%, 97%, 97.3%, 97.6%, 98.0% or a range formed by any two of them. By selecting the above-mentioned types of negative active materials, the secondary battery has higher energy density while considering the structural stability of the negative electrode sheet.

[0034] In one or more embodiments, the electrode assembly comprises a positive electrode sheet, the ratio of the volume percentage of the negative electrode sheet to the volume percentage of the positive electrode sheet is F, 0.5≤F≤1.2, preferably 0.8≤F≤1.2, for example, the value of F can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2 or a range formed by any two of them. By adjusting the ratio of the volume percentage of the negative electrode sheet to the volume percentage of the positive electrode sheet within the above range, the volume percentage of the positive electrode sheet and the negative electrode sheet is within a suitable range, which improves the mechanical safety performance of the electrode assembly while considering the energy density of the cylindrical secondary battery.

[0035] In one or more embodiments, the thickness of the positive electrode sheet is Gμm, 150≤G≤350, for example, the value of G can be 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350 or a range formed by any two of them. By controlling the thickness of the positive electrode sheet within the above range, it is beneficial to improve the support strength of the positive electrode sheet to the electrode assembly, which improves the mechanical safety performance of the cylindrical secondary battery while considering the energy density of the cylindrical secondary battery.

[0036] In one or more embodiments, the positive electrode tab includes a positive current collector, the positive current collector has a thickness of H pm, 8≤H≤15, for example, the value of H can be 8, 8.3, 8.6, 9, 9.3, 9.6, 10, 10.3, 10.6, 11, 11.3, 11.6, 12, 12.3, 12.6, 13, 13.3, 13.6, 14, 14.3, 14.6, 15, or a range between any two of them. By controlling the thickness of the positive current collector in the positive electrode tab within the above range, the support strength of the positive current collector to the electrode assembly is improved, the risk of the energy density of the cylindrical secondary battery being reduced due to the thickness of the positive current collector being too high is reduced, the mechanical safety performance of the cylindrical secondary battery is improved while the energy density of the cylindrical secondary battery is taken into account. The application does not limit the regulation method of the positive current collector, for example, the thickness of the positive current collector can be determined by selecting a commercially available current collector with different thicknesses and combining the test method of "D, C, B, E, F, G, H test" in the application, and then selecting the positive current collector with the required thickness.

[0037] In the present application, "the negative electrode plate includes a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of itself, or can be arranged on two surfaces of the negative electrode current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a partial area of ​​the surface of the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the type of material of the negative electrode current collector, as long as the purpose of this application can be achieved. For example, the negative electrode current collector can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper or a composite current collector (such as a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.). Optionally, the negative electrode material layer may also include a negative electrode binder and a conductive agent. This application has no special restrictions on the type of negative electrode binder in the negative electrode material layer, as long as the purpose of this application can be achieved. For example, the negative electrode binder may include but is not limited to at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene. The present application does not particularly limit the type of conductive agent in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent may include but is not limited to at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metal materials or conductive polymers. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powder and / or metal fibers, specifically, the metal may include but are not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymer may include but is not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. In the present application, the negative electrode material layer also includes a thickener. The present application does not specifically limit the type of thickener, as long as it can achieve the objectives of this application. For example, the thickener may include, but is not limited to, at least one of carboxymethyl cellulose or sodium carboxymethyl cellulose. The present application does not specifically limit the mass ratio of the negative electrode active material, conductive agent, negative electrode binder, and thickener in the negative electrode material layer, as long as it can achieve the objectives of this application.

[0038] The present application does not impose any particular restrictions on the method for preparing the negative electrode sheet, as long as the purpose of the present application can be achieved. For example, the method for preparing the negative electrode sheet may include, but is not limited to, the following steps: (1) mixing the negative electrode active material, the negative electrode binder, the conductive agent, and the thickener in a certain proportion, adding a solvent and stirring evenly to prepare a negative electrode slurry; (2) coating the negative electrode slurry on one surface of the negative electrode current collector, and drying to obtain a negative electrode sheet coated with a negative electrode material layer on one side; (3) repeating the above steps on the other surface of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode material layer on both sides; (4) cold pressing and cutting to obtain the negative electrode sheet.

[0039] In the present application, the volume proportion D of the negative electrode current collector can be controlled by regulating the length and thickness of the negative electrode current collector, and the volume proportion C of the negative electrode material layer can be controlled by regulating the length of the area where the negative electrode slurry is coated on the surface of the negative electrode current collector, the coating weight per unit area of ​​the negative electrode material layer, or the compaction density. The present application has no special restrictions on the negative electrode slurry and the solid content of the negative electrode slurry in the above step (1), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the solvent in the above step (1), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the time and temperature of the drying in the above steps (2) and (3), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the process parameters of the cold pressing in the above step (3), as long as the purpose of the present application can be achieved. The thickness of the negative electrode sheet is the sum of the thickness of the negative electrode current collector and the thickness of the negative electrode material layer. The thickness of the negative electrode material layer is regulated by means known to those skilled in the art. For example, when the negative electrode slurry is coated on the surface of the negative electrode current collector, on the basis of a certain solid content of the negative electrode slurry, the thickness of the negative electrode material layer can be increased by increasing the coating weight per unit area of ​​the negative electrode material layer, and the thickness of the negative electrode material layer can be reduced by reducing the coating weight per unit area of ​​the negative electrode material layer. When other conditions remain constant, the thickness of the negative electrode material layer can be reduced by increasing the compaction density when the negative electrode sheet is cold pressed, and the thickness of the negative electrode material layer can be increased by reducing the compaction density.

[0040] In the present application, the positive electrode plate includes a positive electrode current collector and a positive electrode material layer located on at least one surface of the positive electrode current collector, that is, the positive electrode material layer can be arranged on one surface of the positive electrode current collector along the thickness direction of itself, or on two surfaces of the positive electrode current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector, or it can be a partial area of ​​the surface of the positive electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the type of positive electrode current collector, as long as the purpose of this application can be achieved. For example, the positive electrode current collector may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector), etc. As long as the purpose of this application can be achieved. This application has no special restrictions on the type of positive electrode active material, as long as the purpose of this application can be achieved. For example, the positive electrode active material may include lithium nickel cobalt manganese oxide (LiNi 0.90 Co 0.05 Mn 0.05 O2 (NCM955), NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate or lithium titanate, etc. In the present application, the positive electrode active material may also contain non-metallic elements, for example, non-metallic elements include at least one of fluorine, phosphorus, boron, chlorine, silicon or sulfur. In the present application, the positive electrode material layer may also include a positive electrode binder and a conductive agent. The present application has no special restrictions on the type of positive electrode binder in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the positive electrode binder may be the same type as the negative electrode binder in the above-mentioned negative electrode material layer. The present application has no special restrictions on the type of conductive agent in the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the conductive agent may be the same type as the conductive agent in the above-mentioned negative electrode material layer.

[0041] The present application does not particularly limit the preparation method of the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the preparation method of the positive electrode sheet may include but is not limited to the following steps: (1) mixing the positive electrode active material, the positive electrode binder, and the conductive agent, adding a solvent and stirring evenly to prepare a positive electrode slurry; (2) coating the positive electrode slurry on one surface of the positive electrode current collector, and drying to obtain a positive electrode sheet coated with a positive electrode material layer; (3) repeating the above steps on the other surface of the positive electrode current collector to obtain a positive electrode sheet coated with a positive electrode material layer on both sides; (4) cold pressing and cutting to obtain a positive electrode sheet.

[0042] In the present application, the volume ratio of the positive electrode sheet can be controlled by regulating the length and thickness of the positive electrode current collector, the length of the area on which the positive electrode slurry is coated on the surface of the positive electrode current collector, the coating weight per unit area or the compaction density of the positive electrode material layer. The present application has no special restrictions on the positive electrode slurry and the solid content of the positive electrode slurry in the above step (1), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the solvent in the above step (1), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the time and temperature of the drying in the above steps (2) and (3), as long as the purpose of the present application can be achieved. The present application has no special restrictions on the process parameters of the cold pressing in the above step (3), as long as the purpose of the present application can be achieved. The thickness of the positive electrode sheet is the sum of the thickness of the positive electrode current collector and the thickness of the positive electrode material layer. The thickness of the positive electrode material layer is regulated by means known to those skilled in the art. For example, when the positive electrode slurry is coated on the surface of the positive electrode current collector, on the basis of a certain solid content of the positive electrode slurry, the thickness of the positive electrode material layer can be increased by increasing the coating weight per unit area of ​​the positive electrode material layer, and the thickness of the positive electrode material layer can be reduced by reducing the coating weight per unit area of ​​the positive electrode material layer. When other conditions remain constant, the thickness of the positive electrode material layer can be reduced by increasing the compaction density when the positive electrode sheet is cold pressed, and the thickness of the positive electrode material layer can be increased by reducing the compaction density.

[0043] The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, the material of the diaphragm may include but is not limited to polyethylene (PE), polypropylene (PP)-based polyolefins (PO), polyesters (such as polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of diaphragm may include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane. The diaphragm of the present application may have a porous structure. The present application has no particular restrictions on the size of the pore size of the porous structure of the diaphragm, as long as the purpose of the present application can be achieved. For example, the size of the pore size can be 0.01 μm to 1 μm. The present application has no particular restrictions on the thickness of the diaphragm, as long as the purpose of the present application can be achieved. For example, the thickness of the diaphragm can be 5 μm to 50 μm.

[0044] The electrolyte in the secondary battery of the present application includes a lithium salt and a non-aqueous solvent. The lithium salt may include at least one of LiPF6, LiNO3, LiBF4, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalatoborate) (LiBOB), lithium bis(trifluoromethanesulfonylimide) (LiTFSI) or lithium difluoroborate. The present application does not limit the content of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The present application has no special restrictions on the non-aqueous solvent, as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent may include but is not limited to at least one of a carbonate compound, a carboxylate compound, an ether compound or other organic solvents. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound, a cyclic carbonate compound or a fluorinated carbonate compound. Above-mentioned linear carbonate compound can include but not limited to at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate or methyl ethyl carbonate.Above-mentioned cyclic carbonate can include but not limited to at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate or vinyl ethylene carbonate.Fluorinated carbonate compound can include but not limited to at least one of fluoroethylene carbonate, 1,2-difluoro ethylene carbonate, 1,1-difluoro ethylene carbonate, 1,1,2-trifluoro ethylene carbonate, 1,1,2,2-tetrafluoro ethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate or trifluoromethyl ethylene carbonate. The carboxylate compound may include but is not limited to at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanoic acid, valerolactone or caprolactone. The ether compound may include but is not limited to at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran or tetrahydrofuran. The other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate.

[0045] The secondary battery of the present application also includes a housing for accommodating the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte, as well as other components of the secondary battery known in the art. This application does not limit these other components. This application does not specifically limit the housing and can be any housing known in the art, as long as it can achieve the purpose of this application.

[0046] The secondary battery of the present application is not particularly limited and may include any device that generates an electrochemical reaction. In one embodiment of the present application, the secondary battery may include, but is not limited to, a sodium ion battery, a lithium ion secondary battery (lithium ion battery), a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0047] The present application does not particularly limit the preparation method of cylindrical secondary batteries, and a preparation method known in the art can be selected as long as the purpose of the present application can be achieved. For example, the preparation method of a cylindrical secondary battery includes but is not limited to the following steps: stacking a diaphragm, a positive electrode sheet, a diaphragm and another diaphragm of a negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly, placing the electrode assembly in a shell, injecting an electrolyte into the shell and sealing it to obtain a secondary battery. Alternatively, stacking a diaphragm, a positive electrode sheet, another diaphragm and a negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly, placing the electrode assembly in a shell, injecting an electrolyte into the shell and sealing it to obtain a secondary battery. In the present application, the value of F can be regulated by regulating the volume ratio of the negative electrode sheet and the volume ratio of the positive electrode sheet.

[0048] A second aspect of the present application provides an electronic device comprising the secondary battery of any of the aforementioned embodiments. The secondary battery of the present application can provide good mechanical safety while balancing energy density. Therefore, the electronic device of the present application has a long service life.

[0049] The electronic device of the present application is not particularly limited and can be any electronic device known in the art. For example, the electronic device can include, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, a power tool, a flashlight, a camera, a large household battery, and a lithium-ion capacitor.

[0050] Example

[0051] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0052] Test methods and equipment:

[0053] A's test:

[0054] At an ambient temperature of 25°C, the lithium-ion batteries in each embodiment and comparative example were discharged at a constant current of 0.2C to 2.5V and then disassembled to obtain the negative electrode sheet. The negative electrode sheet was immersed in a dimethyl carbonate (DMC) solution for 4 hours and then dried. A small disc with a radius of 22.14 mm (area of ​​1540.25 mm) was cut out. 2 ), place it on a balance and weigh it, which is recorded as q1, then wash the negative electrode material layer on the negative electrode sheet, place the negative electrode current collector on a balance and weigh it, which is recorded as q2;

[0055] If the small disc is coated with the negative electrode material layer only on one surface of the current collector, A = (q1-q2) / 1540.25.

[0056] If the small disc is a current collector with negative electrode material layers coated on both surfaces, A = (q1-q2) / (2×1540.25).

[0057] Tests for D, C, B, E, F, G, H:

[0058] At an ambient temperature of 25°C, the lithium-ion batteries of each embodiment and comparative example were discharged at 0.5C to 2.5V and then disassembled to obtain an electrode assembly. The diameter of the circle formed by the outermost circle of the winding structure in the electrode assembly and the height of the electrode assembly were measured. The area of ​​the outer contour formed by the outermost circle of the electrode assembly was then calculated based on the diameter. The volume V mm of the electrode assembly was then obtained by multiplying the outer contour area by the height of the electrode assembly. 3 .

[0059] The positive electrode sheet and the negative electrode sheet were taken out from the electrode assembly respectively, soaked in dimethyl carbonate (DMC) for 20 minutes, and then placed in an oven and dried at 80°C for 12 hours to obtain test samples of the positive electrode sheet and the negative electrode sheet. The coating on the surface of the test sample was cleaned off, and then the thickness of 5 positions in the positive electrode collector or the negative electrode collector was measured with a micrometer caliper, and the average value was calculated to obtain the thickness E of the negative electrode collector and the thickness H of the positive electrode collector. If there is an empty foil area without coating, the empty foil area was directly measured with a micrometer caliper to obtain E and H.

[0060] Measure the length and width of the negative electrode collector in the negative electrode sheet and calculate the total area of ​​the negative electrode collector S1 mm 2 Calculate the volume percentage of the negative electrode current collector according to the following expression: D = S1 × E / V. Measure the length and width of the coating area on both surfaces of the negative electrode sheet and calculate the area of ​​the negative electrode material layer on each surface of the negative electrode current collector S2mm. 2 and S3 mm 2The length of the part of the negative electrode tab in which the negative electrode current collector is coated with a negative electrode material layer on both surfaces of the negative electrode current collector is measured, the length is divided into ten equal parts, any point in each equal part is measured with a vernier caliper, and an average value is obtained to obtain the thickness B of the part. The volume ratio of the negative electrode material layer is calculated according to the following expression: C = (S2 x B / 2 + S3 x B / 2) / V.

[0061] The length and width of the positive electrode current collector in the positive electrode tab are measured, and the total area S3 mm of the positive electrode current collector is calculated. 2 The volume ratio of the positive electrode current collector is calculated according to the following expression: J = S3 x H / V. The length and width of the coating area on the two surfaces of the positive electrode tab are measured, and the areas S4 mm and S5 mm of the positive electrode material layer on the two surfaces of the positive electrode current collector are calculated, respectively. 2 2 The length of the part of the positive electrode tab in which the positive electrode current collector is coated with a positive electrode material layer on both surfaces of the positive electrode current collector is measured, the length is divided into ten equal parts, any point in each equal part is measured with a vernier caliper, and an average value is obtained to obtain the thickness G of the part. The volume ratio of the positive electrode material layer is calculated according to the following expression: K = (S4 x G / 2 + S5 x G / 2) / V. Then, F can be calculated according to the following expression: F = (D + C) / (J + K).

[0062] Impact test:

[0063] After the lithium ion battery is charged at 1C constant current to 4.2V, it is charged at constant voltage to 0.05C to reach the full charge state. In a room temperature environment of 25°C, the lithium ion battery in the full charge state is placed on the test table, and a round rod with a diameter of 15.8mm and a length of at least 6cm is placed at the center position of the wide surface of the lithium ion battery. The longitudinal axis of the lithium ion battery is parallel to the surface of the test table and perpendicular to the longitudinal axis of the round rod. A weight of 9.1kg is used to drop vertically from a height of 610mm in a free state, and the round rod and the lithium ion battery intersect. In addition, the average temperature of the electrode assembly (the temperature sensing wire is attached to the electrode assembly, and a multichannel temperature measuring instrument is used to measure and record the average temperature of a single electrode assembly within 10min from the start of the impact test, and when the electrode assembly catches fire, the temperature cannot be measured and is recorded as thermal runaway), voltage and deformation are recorded. The deformation is the maximum distance between the concave deformation of the lithium ion battery shell and the original wide surface of the lithium ion battery on which the round rod is placed in the vertical direction.

[0064] Test pass judgment criteria: no fire, no explosion and no current interruption device overturning. Among them, the current interruption device overturning can be judged by the change of voltage.

[0065] ​Sixteen lithium-ion batteries were tested for each Example or Comparative Example. The impact pass rate of the lithium-ion battery = the number of batteries that passed / 16; the average temperature of the electrode assembly of the lithium-ion battery = the sum of the average temperatures of the electrode assemblies of each lithium-ion battery over a 10-minute period / 16; and the average deformation of the electrode assembly of the lithium-ion battery = the sum of the deformations of the electrode assemblies of each lithium-ion battery / 16. A higher impact pass rate (i.e., a greater number of batteries that passed) indicates better mechanical safety performance of the lithium-ion battery.

[0066] Volume energy density test:

[0067] At an ambient temperature of 25°C, the lithium-ion battery is charged to 4.2V at a current of 0.5C, and then charged to 0.05C at a constant voltage of 4.2V; let it stand for 5 minutes, and then discharge it to 2.5V at a constant current of 0.02C, let it stand for 5 minutes, and record the capacity at this time as O, in mAh. Then the lithium-ion battery is charged to 3.6V at 0.5C, and the volume energy density is calculated: VED = (O × P × 1000) / V', in Wh / L, where P is the system platform voltage and V' is the volume of the lithium-ion battery (i.e., the length × width × thickness of the shell).

[0068] Example 1-1

[0069] <Preparation of negative electrode sheet>

[0070] The negative electrode active materials artificial graphite, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:1.7:2.3, and then deionized water is added as a solvent, stirred and mixed evenly to obtain a negative electrode slurry with a solid content of 50wt%. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness E of 10μm, and dried at 105°C to obtain a negative electrode sheet coated with a negative electrode material layer on one side. Thereafter, the above steps are repeated on the other surface of the negative electrode current collector copper foil to obtain a negative electrode sheet coated with a negative electrode material layer on both sides. Then, after cold pressing, cutting and slitting, a negative electrode sheet with a size of 1500mm×62mm is obtained. Among them, the unit area coating weight A of the negative electrode material layer is 175mg / 1540mm 2 After cold pressing, the thickness of the single-sided negative electrode material layer is 82.5μm, the thickness B of the negative electrode sheet is 175μm, and the compaction density of the negative electrode material layer is 1.4g / cm 3 The specifications of the negative electrode material layer are 1500mm×60mm.

[0071] <Preparation of positive electrode sheet>

[0072] The positive electrode active material lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1O2), binder polyvinylidene fluoride (PVDF) and conductive carbon black are dispersed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 94.8:2.8:2.4, and the mixture is stirred thoroughly to obtain a positive electrode slurry with a solid content of 72wt%. The positive electrode slurry is evenly coated on one surface of the positive electrode collector aluminum foil with a thickness H of 11μm, and dried at 105°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. The above steps are then repeated on the other surface of the positive electrode collector aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. Then, after cold pressing, cutting, and slitting, it is dried under vacuum conditions at 105°C for 4h to obtain a positive electrode sheet with a size of 1450mm×60mm, wherein the unit area coating weight of the positive electrode material layer is 450mg / 1540mm 2 After cold pressing, the thickness of the single-sided positive electrode material layer is 119.5μm, the thickness G of the positive electrode sheet is 250μm, and the compaction density of the positive electrode material layer is 2.5g / cm 3 The specifications of the positive electrode material layer are 1450mm×60mm.

[0073] <Diaphragm>

[0074] A polyethylene (PE) film with a thickness of 12 μm was used as the separator.

[0075] <Preparation of Electrolyte>

[0076] In a dry argon atmosphere glove box, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 30:50:20 to create a base solvent. Lithium hexafluorophosphate (LiPF6) was then added to the base solvent and thoroughly mixed to create an electrolyte. The mass percentage of LiPF6 in the electrolyte was 12.5%, with the remainder being the base solvent.

[0077] <Preparation of lithium-ion batteries>

[0078] The prepared diaphragm, positive electrode sheet, diaphragm, and negative electrode sheet are stacked in order, with the diaphragm positioned between the positive and negative electrodes to act as a barrier. After winding, flattening, current collector plate welding, shell insertion, bottom penetration welding, inkjet printing, vacuum drying, electrolyte injection, cap welding, sealing, and high-temperature stabilization, a lithium-ion battery with a volume of 0.025L is obtained. The upper limit of the formation voltage is 3.6V, the formation temperature is 45°C, and the formation is allowed to stand at room temperature of 25°C for 24 hours.

[0079] Example 1-2 to Example 1-23

[0080] The preparation parameters were the same as those in Example 1-1, except that they were adjusted according to Table 1. When the thickness G of the positive electrode sheet changed, the coating weight per unit area of ​​the positive electrode material layer was adjusted so that the value of G was as shown in Table 1. In Examples 1-22 and 1-23, the coating weight per unit area of ​​the negative electrode material layer was adjusted according to Table 1, and the compaction density of the negative electrode material layer was adjusted so that the thickness B of the negative electrode sheet was as shown in Table 1.

[0081] Comparative Examples 1 to 3

[0082] Except for adjusting the relevant preparation parameters according to Table 1, the rest is the same as Example 1-1.

[0083]

[0084]

[0085] From Examples 1-1 to 1-23 and Comparative Examples 1 to 3, it can be seen that by adjusting the value of 3D-0.2C within the scope of this application, the deformation of the electrode assembly is small and the average temperature is low, and the impact pass rate of the lithium-ion battery is improved, indicating that the negative electrode current collector has a good support effect on the electrode assembly. At this time, the electrode assembly has good rigidity, and the mechanical safety performance of the lithium-ion battery is high while taking into account the energy density of the lithium-ion battery. The values ​​of 3D-0.2C in Comparative Examples 1 to 3 are not within the scope of this application. In Comparative Examples 1 to 2, the rigidity of the electrode assembly is poor. During the impact test, the deformation of the electrode assembly is large, and the impact test cannot be passed due to thermal runaway. At this time, the mechanical safety performance of the lithium-ion battery is poor. The energy density of Comparative Example 3 is low and does not meet actual production requirements. In contrast, the energy density of the lithium-ion battery in Examples 1 to 23 is high and the impact test pass rate is high, indicating that the lithium-ion battery of this application has good mechanical safety performance while taking into account the energy density of the lithium-ion battery.

[0086] The value of D and the value of C usually affect the energy density and mechanical safety performance of lithium-ion batteries. It can be seen from Examples 1-1 to 1-13, and Examples 1-16 to 1-23 that when the value of D and the value of C are within the application range, while taking into account the high energy density, it is beneficial to improve the mechanical safety performance of the lithium-ion battery. Among them, in Examples 1-2, 1-3 and 1-17, due to the low value of D and the low rigidity of the electrode assembly, some electrode assemblies failed in the impact test, and the deformation of the failed electrode assembly was high. In addition, the short circuit of the failed electrode assembly caused the average temperature of the electrode assembly within 10 minutes to be high, which in turn caused the average temperature of the 16 electrode assemblies and the deformation of the electrode assembly to be high. In Examples 1-7, 1-12 and 1-13, due to the high value of D and the high support strength, the deformation of the electrode assembly was low and the mechanical safety performance was high, but the energy density was low.

[0087] The value of A usually affects the energy density and mechanical safety performance of lithium-ion batteries. From Examples 1-1, 1-2, 1-4, 1-8 to 1-13, and 1-20 to 1-23, it can be seen that when the value of A is within the application range, it is beneficial to improve the mechanical safety performance of lithium-ion batteries while maintaining a high energy density. Among them, in Examples 1-8 and 1-20, due to the low value of A, the coating weight per unit area of ​​the negative electrode material layer is low, and the thickness of the negative electrode sheet is low, resulting in a low energy density.

[0088] The B / A value generally affects the energy density and mechanical safety performance of lithium-ion batteries. As can be seen from Examples 1-1, 1-2, 1-5, 1-22, and 1-23, when the B / A value is within the applicable range, it is beneficial to improve the mechanical safety performance of lithium-ion batteries while maintaining a high energy density.

[0089] The value of E generally affects the energy density and mechanical safety performance of lithium-ion batteries. It can be seen from Examples 1-1 to 1-7, 1-12, 1-13, 1-20, and 1-21 that when the value of E is within the applicable range, it is beneficial to improve the mechanical safety performance of lithium-ion batteries while maintaining a high energy density.

[0090] The mass percentage of the negative electrode active material generally affects the energy density of a lithium-ion battery. As can be seen from Examples 1-1, 1-14, and 1-15, when the mass percentage of the negative electrode active material is within the specified range, the lithium-ion battery can achieve both a high energy density and mechanical safety.

[0091] The value of F generally affects the energy density and mechanical safety performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-2, Example 1-4, Example 1-5, Example 1-7 to Example 1-13, Example 1-16, Example 1-17, Example 1-20 to Example 1-23, when the value of F is within the scope of the application, the mechanical safety performance of the lithium ion battery is improved while the energy density is maintained at a high level.

[0092] The value of G generally affects the energy density and mechanical safety performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-7, Example 1-9 to Example 1-12, Example 1-16, Example 1-17, Example 1-20 to Example 1-22, when the value of G is within the scope of the application, the mechanical safety performance of the lithium ion battery is improved while the energy density is maintained at a high level.

[0093] The value of H generally affects the energy density and mechanical safety performance of the lithium ion battery. As can be seen from Example 1-1, Example 1-18 and Example 1-19, when the value of H is within the scope of the application, the mechanical safety performance of the lithium ion battery is improved while the energy density is maintained at a high level.

[0094] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0095] Each of the embodiments in the specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0096] The above is only the preferred embodiment of the present application, and does not limit the present application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A cylindrical secondary battery, comprising an electrode assembly, the electrode assembly comprising a negative electrode pole piece, the negative electrode pole piece comprising a negative electrode current collector and a negative electrode material layer located on at least one surface of the negative electrode current collector, wherein, based on the volume of the electrode assembly, the volume of the negative electrode current collector accounts for D%, and the volume of the negative electrode material layer accounts for C%, where -3≤3D-0.2C≤12.

2. The cylindrical secondary battery according to claim 1, wherein 2≤D≤6,30≤C≤45.

3. The cylindrical secondary battery according to claim 1, wherein 3≤3D-0.2C≤10.

4. The cylindrical secondary battery according to any one of claims 1 to 3, wherein The cylindrical secondary battery satisfies at least one of the following characteristics: (1)5≤3D-0.2C≤9; (2)3≤D≤5； (3)35≤C≤40。 5. The cylindrical secondary battery according to any one of claims 1 to 4, wherein The coating weight per unit area of ​​the negative electrode material layer is A mg / 1540 mm 2 , 100≤A≤250.

6. The cylindrical secondary battery according to any one of claims 1 to 5, wherein The thickness of the negative electrode plate is B μm, 0.5≤B / A≤1.

5.

7. The cylindrical secondary battery according to claim 6, wherein 0.8≤B / A≤1.

2.

8. The cylindrical secondary battery according to any one of claims 1 to 7, wherein The thickness of the negative electrode current collector is E μm, 5≤E≤15.

9. The cylindrical secondary battery according to claim 8, wherein 8≤E≤12。 10. The cylindrical secondary battery according to any one of claims 1 to 9, wherein The negative electrode material layer includes a negative electrode active material, which includes at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon oxygen or silicon carbon composite. Based on the mass of the negative electrode material layer, the mass percentage of the negative electrode active material is 95.0% to 98.0%.

11. The cylindrical secondary battery according to any one of claims 1 to 10, wherein the electrode assembly comprises a positive electrode sheet, and based on the volume of the electrode assembly, a ratio of a volume share of the negative electrode sheet to a volume share of the positive electrode sheet is F, and 0.5≤F≤1.

2.

12. The cylindrical secondary battery according to claim 11, wherein 0.8≤F≤1.2。 13. The cylindrical secondary battery according to claim 11 or 12, wherein The thickness of the positive electrode plate is G μm, 150≤G≤350.

14. The cylindrical secondary battery according to any one of claims 11 to 13, wherein The positive electrode plate includes a positive electrode current collector, and the positive electrode current collector has a thickness of H μm, 8≤H≤15. 15 . An electronic device comprising the cylindrical secondary battery according to claim 1 .

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