Cylindrical secondary battery and electric device

Abstract

The invention provides a cylindrical secondary battery and a power utilization device, and the cylindrical secondary battery comprises a housing which comprises a side wall and a bottom wall; the electrode assembly is arranged in the shell; the filling layer comprises a first filling layer and a second filling layer which are connected with each other, the first filling layer is located between the electrode assembly and the side wall in the circumferential direction of the side wall, and the second filling layer is located between the electrode assembly and the bottom wall; the filling layer comprises an elastic porous insulating material. The cylindrical secondary battery provided by the invention has good safety performance, cycle performance and energy density.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to a cylindrical secondary battery and an electrical device. Background Art

[0002] Cylindrical secondary batteries, such as cylindrical lithium-ion batteries, have the characteristics of large specific energy, high operating voltage, low self-discharge rate, small size, light weight, etc., and are widely used in the field of consumer electronics.

[0003] However, in the later stages of the cycle of cylindrical lithium-ion batteries, the cycle performance and safety performance are affected due to battery expansion and electrolyte consumption. Summary of the invention

[0004] The purpose of this application is to provide a cylindrical secondary battery and an electrical device to improve the energy density, cycle performance and safety performance of the cylindrical secondary battery. The specific technical solution is as follows:

[0005] In a first aspect, the present application provides a cylindrical secondary battery, which includes: a shell, including side walls and a bottom wall; an electrode assembly, arranged in the shell; a filling layer, including a first filling layer and a second filling layer connected to each other, the first filling layer is located between the electrode assembly and the side wall along the circumference of the side wall, and the second filling layer is located between the electrode assembly and the bottom wall; the filling layer includes an elastic porous insulating material.

[0006] The present application sets a first filling layer between the electrode assembly and the side wall, and a second filling layer between the electrode assembly and the bottom wall, and the first filling layer and the second filling layer are interconnected, and the filling layer includes an elastic porous insulating material, so that the first filling layer and the second filling layer form an uninterrupted and dynamically deformable buffer layer around and at the bottom of the electrode assembly. When the cylindrical secondary battery undergoes Joule relaxation expansion during the charging and discharging process, the dynamic deformation of the first filling layer can effectively absorb the expansion force of the cylindrical secondary battery, reduce the risk of shell expansion, and reduce the accumulation of internal pressure of the cylindrical secondary battery; the dynamic deformation of the second filling layer can effectively reduce the risk of damage to the cylindrical secondary battery due to shock or falling, and improve the deformation resistance and drop resistance of the cylindrical secondary battery; at the same time, the filling layer including the elastic porous insulating material has good thermal insulation and flame retardant properties, and can play an effective thermal insulation and flame retardant role when the cylindrical secondary battery is in thermal runaway or there is a threat of external fire source, thereby helping to improve the safety performance of the cylindrical secondary battery. The porous structure of the elastic porous insulating material can improve the liquid absorption capacity of the filling layer. The dynamic deformation of the elastic porous insulating material allows it to dynamically release electrolyte according to the expansion degree of the cylindrical secondary battery, so that the cylindrical secondary battery has sufficient electrolyte to participate in the electrochemical reaction during the cycle, especially in the late cycle, thereby improving the cycle performance of the cylindrical secondary battery. At the same time, based on the filling layer, the expansion of the cylindrical secondary battery can be better alleviated, the volume of the electrode assembly can be increased, and the group margin in the shell can be reduced, thereby improving the cycle performance of the cylindrical secondary battery while also improving the energy density of the cylindrical secondary battery.

[0007] In some embodiments, the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet includes a positive electrode active material layer, and the negative electrode sheet includes a negative electrode active material layer; along the direction of the bottom wall pointing to the electrode assembly, the edge of the first filling layer away from the bottom wall is the first edge, the edge of the positive electrode active material layer away from the bottom wall is the second edge, and the edge of the negative electrode active material layer away from the bottom wall is the third edge, the third edge is higher than the second edge, and the first edge is located between the second edge and the third edge.

[0008] The present application controls the first edge to be located between the second edge and the third edge. During the charge and discharge process, the electrode assembly expands, and the first filling layer can promote higher interface affinity and more complete interface reaction, which can alleviate the lithium precipitation phenomenon of the cylindrical secondary battery and improve the energy density of the cylindrical secondary battery. After the electrode assembly is cycled, the negative electrode sheet in the negative electrode super-positive electrode region has the risk of collapse, and there is a risk of contacting the positive electrode sheet after the negative electrode sheet collapses; the first edge is controlled to be located between the second edge and the third edge. After the electrode assembly cyclically expands, the positive electrode sheet can be squeezed on the first filling layer, so that if the negative electrode sheet collapses, it also contacts the first filling layer. Based on the insulation of the first filling layer, the risk of the negative electrode sheet contacting the positive electrode sheet can be reduced, and the risk of short circuit can be reduced; at the same time, the first filling layer has good coating, which can make the overall temperature distribution of the electrode assembly uniform, reduce the side reaction of the electrode assembly corner, and reduce the risk of lithium precipitation at the electrode assembly corner, thereby improving the safety performance of the cylindrical secondary battery.

[0009] In some embodiments, the cylindrical secondary battery is a square shell battery, and the side walls include a first side wall, a second side wall, a third side wall and a fourth side wall, the first side wall connects the second side wall and the fourth side wall, the third side wall connects the second side wall and the fourth side wall, the first side wall and the third side wall are arranged along a first direction, the second side wall and the fourth side wall are arranged along a second direction, and the size of the first side wall along the second direction is greater than the size of the second side wall along the first direction; the first filling layer includes a first part, a second part, a third part and a fourth part; along the first direction, the first part is arranged between the first side wall and the electrode assembly, and the third part is arranged between the electrode assembly and the third side wall; along the second direction, the second part is arranged between the second side wall and the electrode assembly, and the fourth part is arranged between the electrode assembly and the fourth side wall.

[0010] In some embodiments, along the first direction, the thickness of the first part is H11mm, the thickness of the electrode assembly is H0mm, and 0.015≤H11 / H0≤0.03. The present application adjusts the value of the ratio H11 / H0 of the thickness of the first part and the thickness of the electrode assembly within the above range, so that the first part has a good ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly during the charge and discharge process, and can also improve the infiltration effect of the electrolyte in the electrode assembly, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0011] In some embodiments, along the first direction, the thickness of the third portion is H13 mm, the thickness of the electrode assembly is H0 mm, and 0.015≤H13 / H0≤0.03. The present application adjusts the value of the ratio H13 / H0 of the thickness of the third portion and the thickness of the electrode assembly within the above range, so that the third portion has a good ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly during the charge and discharge process, and can also improve the infiltration effect of the electrolyte in the electrode assembly, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0012] In some embodiments, along the first direction, the thickness of the first part is H11mm, the thickness of the third part is H13mm, the thickness of the electrode assembly is H0mm, 0.015≤H11 / H0≤0.03, 0.015≤H13 / H0≤0.03. The present application adjusts the ratio of the thickness of the first part to the thickness of the electrode assembly H11 / H0 and the ratio of the thickness of the third part to the thickness of the electrode assembly H13 / H0 within the above range, so that the first part and the third part have better ability to absorb and store electrolyte, better absorb the expansion force of the electrode assembly during the charge and discharge process, and can further enhance the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0013] In some embodiments, 0.45≤H11≤2.1. By adjusting the values ​​of H11 / H0 and H11 within the scope of the present application, the first part can have better liquid absorption capacity and better absorb the expansion force of the electrode assembly during the charge and discharge process, and can further improve the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0014] In some embodiments, 0.45≤H13≤2.1. By adjusting the values ​​of H13 / H0 and H13 within the scope of the present application, the third part can have better liquid absorption capacity and better absorb the expansion force of the electrode assembly during the charge and discharge process, and can further improve the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0015] In some embodiments, 0.45≤H11≤2.1, 0.45≤H13≤2.1. By adjusting the values ​​of H11 / H0 and H11, H13 / H0 and thickness H13 within the scope of the present application, the first part and the third part can have better liquid absorption capacity, better absorb the expansion force of the electrode assembly during the charge and discharge process, and further enhance the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0016] In some embodiments, along the second direction, the thickness of the second part is H12mm, 0.33≤H12 / H11≤1. By regulating H12 / H11 within the above range, the present application can better alleviate the expansion of the cylindrical secondary battery along the first direction, better exert the ability of the filling layer to absorb the expansion force of the electrode assembly during the charging and discharging process, and further reduce the risk of lithium deposition at the corners of the electrode assembly, thereby further improving the safety performance of the cylindrical secondary battery. At the same time, the first part and the second part can better absorb and store the electrolyte, and make the electrolyte have a better infiltration effect in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0017] In some embodiments, along the second direction, the thickness of the fourth part is H14mm, 0.33≤H14 / H11≤1. By regulating H14 / H11 within the above range, the present application can better alleviate the expansion of the cylindrical secondary battery along the first direction, better exert the ability of the filling layer to absorb the expansion force of the electrode assembly during the charging and discharging process, and further reduce the risk of lithium deposition at the corners of the electrode assembly, thereby further improving the safety performance of the cylindrical secondary battery. At the same time, the first part and the fourth part can better absorb and store the electrolyte, and make the electrolyte have a better infiltration effect in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0018] In some embodiments, 0.15≤H12≤1.5. The present application regulates the values ​​of H12 / H11 and H12 within the scope of the present application, which is conducive to further reducing the risk of lithium deposition in the corners of the electrode assembly and improving the safety performance of the cylindrical secondary battery; at the same time, the first part and the second part can better absorb the expansion force of the electrode assembly during the charging and discharging process, and have better liquid absorption capacity, and can further enhance the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the safety performance and cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0019] In some embodiments, 0.15≤H14≤1.5. The present application regulates the values ​​of H14 / H11 and H14 within the scope of the present application, which is conducive to further reducing the risk of lithium deposition in the corners of the electrode assembly and improving the safety performance of the cylindrical secondary battery; at the same time, the first part and the second part can better absorb the expansion force of the electrode assembly during the charging and discharging process, and have better liquid absorption capacity, and can further enhance the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the safety performance and cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0020] In some embodiments, the thickness of the second filling layer is H21mm, 0.5≤H21 / H11≤1. By adjusting the value of H21 / H11 within the above range, the present application can make the second filling layer more effectively reduce the risk of damage to the cylindrical secondary battery during shock or fall, so that the cylindrical secondary battery has better resistance to deformation and fall, and at the same time, the first part has better absorption of the expansion force of the electrode assembly during the charging and discharging process, thereby further improving the safety performance of the cylindrical secondary battery. It is also possible to make the second filling layer and the first filling layer have better liquid absorption capacity at the same time, which is conducive to improving the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0021] In some embodiments, 0.23≤H21≤1.5. In the present application, by adjusting the value of H21 within the above range, the second filling layer can further reduce the risk of damage to the cylindrical secondary battery during shock or fall, further improve the ability of the cylindrical secondary battery to resist deformation and fall, and thus further improve the safety performance of the cylindrical secondary battery. At the same time, the second filling layer can exert a better liquid absorption ability, which is conducive to improving the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0022] In some embodiments, the cylindrical secondary battery is a cylindrical battery, and along the radial direction of the cylindrical battery, the thickness of the first filling layer is H10mm, the diameter of the electrode assembly is Dmm, and 0.02≤H10 / D≤0.04. The present application adjusts the value of H10 / D within the above range, so that the first filling layer can play a better ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly during the charge and discharge process, and can also improve the infiltration effect of the electrolyte in the electrode assembly, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0023] In some embodiments, 15≤D≤65. By adjusting the value of D within the above range, the present application can make the first filling layer have better liquid absorption capacity and better absorb the expansion force of the electrode assembly during the charge and discharge process, and can further improve the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0024] In some embodiments, the thickness of the second filling layer is H20mm, and 0.33≤H20 / H10≤1. By adjusting the value of H20 / H10 within the above range, the present application can make the second filling layer more effectively reduce the risk of damage to the cylindrical secondary battery during shock or fall, and make the cylindrical secondary battery have better resistance to deformation and fall, while making the first filling layer better able to absorb the expansion force of the electrode assembly during the charging and discharging process, thereby further improving the safety performance of the cylindrical secondary battery. It is also possible to make the second filling layer and the first filling layer simultaneously exert better liquid absorption capacity, which is beneficial to improving the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0025] In some embodiments, 0.1≤H20≤1.5. In the present application, by adjusting the value of H20 within the above range, the second filling layer can further reduce the risk of damage to the cylindrical secondary battery during shock or fall, further improve the ability of the cylindrical secondary battery to resist deformation and fall, and thus further improve the safety performance of the cylindrical secondary battery. At the same time, the second filling layer can exert a better liquid absorption ability, which is conducive to improving the infiltration effect of the electrolyte in the electrode assembly, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0026] In some embodiments, the average pore size of the filling layer is dμm, 25≤d≤35. The present application can make the filling layer have good mechanical strength and buffering performance by regulating the value of the average pore size d of the filling layer within the above range, and at the same time facilitate the absorption and release of the electrolyte, so that the filling layer has good ability to dynamically release the electrolyte, and the electrolyte can be evenly distributed, which is conducive to improving the infiltration effect of the electrolyte in the electrode assembly, so that the filling layer can take into account the liquid absorption capacity, mechanical properties and safety performance at the same time, thereby making the cylindrical secondary battery have good energy density, cycle performance and safety performance.

[0027] In some embodiments, the porosity of the filling layer is P%, 55≤P≤65. The present application can make the filling layer have good mechanical strength and buffering performance by regulating the value of the porosity P of the filling layer within the above range, and at the same time facilitate the absorption and release of the electrolyte, so that the filling layer has good ability to dynamically release the electrolyte, and the electrolyte can be evenly distributed, which is conducive to improving the infiltration effect of the electrolyte in the electrode assembly, so that the filling layer can take into account the liquid absorption capacity, mechanical properties and safety performance at the same time, thereby making the cylindrical secondary battery have good energy density, cycle performance and safety performance.

[0028] In some embodiments, the compression rate of the filling layer is Y%, 35≤Y≤45. By regulating the compression rate of the filling layer within the above range, the present application can make the filling layer have good mechanical strength, improve the filling layer's ability to absorb the expansion force of the electrode assembly during the charging and discharging process, play a good buffering effect, reduce the risk of shell deformation, and enable the filling layer to maintain its pore structure in a compressed state, which can improve the ability of the electrolyte to dynamically release, which is beneficial to improving the wettability of the electrolyte in the electrode assembly, thereby improving the safety performance and cycle performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0029] In some embodiments, the elastic porous insulating material includes at least one of ethylene-vinyl acetate copolymer, polystyrene, polyvinyl chloride, polyacrylic acid, polyvinyl alcohol, polyurethane or polyethylene terephthalate. The above elastic porous insulating material has good elastic deformation properties, heat insulation properties, flame retardant properties, and electrolyte corrosion resistance. The present application adopts the above-mentioned types of elastic porous insulating materials, which can improve the filling layer's ability to absorb the expansion force of the electrode assembly during the charging and discharging process, and can also improve the thermal insulation and flame retardant properties of the cylindrical secondary battery. At the same time, it can improve the liquid absorption capacity of the filling layer, and make the filling layer have a good ability to dynamically release the electrolyte, so that the cylindrical secondary battery can have good energy density, cycle performance and safety performance at the same time.

[0030] A second aspect of the present application provides an electrical device, which includes the cylindrical secondary battery provided in the first aspect of the present application.

[0031] The present application provides a cylindrical secondary battery and an electrical device, the cylindrical secondary battery comprising: a shell, comprising side walls and a bottom wall; an electrode assembly, arranged in the shell; a filling layer, comprising a first filling layer and a second filling layer connected to each other, the first filling layer being located between the electrode assembly and the side wall along the circumference of the side wall, and the second filling layer being located between the electrode assembly and the bottom wall; the filling layer comprising an elastic porous insulating material. The present application sets a first filling layer between the electrode assembly and the side wall, and a second filling layer between the electrode assembly and the bottom wall, and the first filling layer and the second filling layer are connected to each other, and the filling layer includes an elastic porous insulating material, so that the first filling layer and the second filling layer form a dynamically deformable buffer layer around and at the bottom of the electrode assembly. The dynamic deformation of the first filling layer can effectively absorb the expansion force of the cylindrical secondary battery, reduce the risk of shell expansion, and reduce the accumulation of internal pressure of the cylindrical secondary battery; the dynamic deformation of the second filling layer can effectively reduce the risk of damage to the cylindrical secondary battery due to shock or falling, and improve the deformation resistance and drop resistance of the cylindrical secondary battery; at the same time, the filling layer including the elastic porous insulating material has good thermal insulation and flame retardant properties, and can play an effective thermal insulation and flame retardant role when the cylindrical secondary battery is in thermal runaway or there is a threat of external fire source, thereby improving the safety performance of the cylindrical secondary battery. The porous structure of the elastic porous insulating material can improve the liquid absorption capacity of the filling layer. The dynamic deformation of the elastic porous insulating material allows it to dynamically release electrolyte according to the expansion degree of the cylindrical secondary battery, so that the cylindrical secondary battery has sufficient electrolyte to participate in the electrochemical reaction during the cycle, thereby improving the cycle performance of the cylindrical secondary battery. At the same time, based on the filling layer, the expansion of the cylindrical secondary battery can be better alleviated, the volume of the electrode assembly can be increased, and the group margin in the shell can be reduced, thereby improving the cycle performance of the cylindrical secondary battery while also improving the energy density of the cylindrical secondary battery, thereby making the cylindrical secondary battery of the present application have good safety performance, cycle performance and energy density.

[0032] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0034] Figure 1 A schematic diagram of the three-dimensional structure of a cylindrical secondary battery including a housing, an electrode assembly and a filling layer in one embodiment of the present application;

[0035] Figure 2 for Figure 1A cross-sectional view of a cylindrical secondary battery along the X direction;

[0036] Figure 3 for Figure 1 A cross-sectional view of a cylindrical secondary battery along the Y direction;

[0037] Figure 4 for Figure 1 A top view of a cylindrical secondary battery in FIG.

[0038] Figure 5 A cross-sectional view of a cylindrical secondary battery along the X direction in another embodiment of the present application;

[0039] Figure 6 A cross-sectional view of a cylindrical secondary battery along a diameter direction in another embodiment of the present application;

[0040] Figure 7 for Figure 6 A top view of a cylindrical secondary battery in FIG.

[0041] Figure markings: shell 100, side wall 110, bottom wall 120, first side wall 111, second side wall 112, third side wall 113, fourth side wall 114, electrode assembly 200, positive electrode sheet 210, negative electrode sheet 220, separator 230, positive electrode active material layer 2110, positive electrode collector 2120, second edge 2101, negative electrode active material layer 2210, negative electrode collector 2220, third edge 2201, first electrode assembly 201, second electrode assembly 202, filling layer 300, first filling layer 310, second filling layer 320, first part 311, second part 312, third part 313, fourth part 314, first edge 3101, X direction: thickness direction / diameter direction of the electrode assembly, Y direction: length direction of the electrode assembly, Z direction: height direction of the electrode assembly. DETAILED DESCRIPTION

[0042] The following will be combined with the embodiments of the present application and the accompanying drawings to clearly and completely describe the technical solutions in the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0043] For ease of understanding, in this application, a three-dimensional rectangular coordinate system is established with the thickness direction (or diameter direction) of the electrode assembly as the X direction, the length direction of the electrode assembly as the Y direction, and the height direction of the electrode assembly as the Z direction. The above direction limitation is only used to understand the technical solution of this application and does not limit the protection scope of this application.

[0044] In a first aspect, the present application provides a cylindrical secondary battery, which includes: a shell, an electrode assembly and a filling layer, the shell includes a side wall and a bottom wall, the electrode assembly is arranged in the shell, the filling layer includes a first filling layer and a second filling layer connected to each other, the first filling layer is located between the electrode assembly and the side wall along the circumference of the side wall, and the second filling layer is located between the electrode assembly and the bottom wall; the filling layer includes an elastic porous insulating material. Specifically, as Figures 1 to 7 As shown, the cylindrical secondary battery includes a shell 100, an electrode assembly 200 and a filling layer 300, the shell 100 includes a side wall 110 and a bottom wall 120, the electrode assembly 200 is arranged in the shell 100, and the filling layer 300 includes a first filling layer 310 and a second filling layer 320 connected to each other, the first filling layer 310 is located between the electrode assembly 200 and the side wall 110 along the circumference of the side wall 110, and the second filling layer 320 is located between the electrode assembly 200 and the bottom wall 120; the filling layer 300 includes an elastic porous insulating material. The present application does not specifically limit the type of cylindrical secondary battery, as long as the purpose of the present application can be achieved, for example, the cylindrical secondary battery is a square shell battery or a cylindrical battery. The present invention provides a first filling layer 310 between the electrode assembly 200 and the side wall 110, and a second filling layer 320 between the electrode assembly 200 and the bottom wall 120, and the first filling layer 310 and the second filling layer 320 are connected to each other, and the filling layer includes an elastic porous insulating material, so that the first filling layer 310 and the second filling layer 320 form an uninterrupted and dynamically deformable buffer layer around and at the bottom of the electrode assembly 200. When the cylindrical secondary battery undergoes Joule relaxation during the charge and discharge process, the first filling layer 310 and the second filling layer 320 are connected to each other. When the cylindrical secondary battery is expanded, the dynamic deformation of the first filling layer 310 can effectively absorb the expansion force of the cylindrical secondary battery, reduce the risk of expansion of the shell 100, and reduce the accumulation of internal pressure of the cylindrical secondary battery; the dynamic deformation of the second filling layer 320 can effectively reduce the risk of damage to the cylindrical secondary battery during shock or fall, and improve the anti-deformation and anti-fall capabilities of the cylindrical secondary battery; at the same time, the filling layer 300 including the elastic porous insulating material has good heat insulation and flame retardant properties, which can play an effective role in heat insulation and flame retardancy when the cylindrical secondary battery is thermally runaway or there is a threat of external fire source, thereby helping to improve the safety performance of the cylindrical secondary battery. The porous structure of the elastic porous insulating material can improve the liquid absorption capacity of the filling layer 300, and the dynamic deformation of the elastic porous insulating material allows it to dynamically release the electrolyte according to the expansion degree of the cylindrical secondary battery, so that the cylindrical secondary battery has sufficient electrolyte to participate in the electrochemical reaction during the cycle, especially in the late cycle, thereby improving the cycle performance of the cylindrical secondary battery. At the same time, the filling layer 300 can better alleviate the expansion of the cylindrical secondary battery, increase the volume of the electrode assembly 200, and reduce the group margin in the shell 100, thereby improving the cycle performance of the cylindrical secondary battery and improving the energy density of the cylindrical secondary battery.

[0045] In some embodiments, such as Figures 1 to 7 As shown, the electrode assembly 200 includes a positive electrode sheet 210, a negative electrode sheet 220 and a separator 230. The separator 230 is disposed between the positive electrode sheet 210 and the negative electrode sheet 220. The positive electrode sheet 210 includes a positive electrode active material layer 2110, and the negative electrode sheet 220 includes a negative electrode active material layer 2210. The direction along the bottom wall 120 pointing to the electrode assembly 200 is the same as the height direction of the electrode assembly 200, that is, Figure 1 In the Z direction, the edge of the first filling layer 310 away from the bottom wall 120 is the first edge 3101, the edge of the positive electrode active material layer 2110 away from the bottom wall 120 is the second edge 2101, and the edge of the negative electrode active material layer 2210 away from the bottom wall 120 is the third edge 2201, the third edge 2201 is higher than the second edge 2101, and the first edge 3101 is located between the second edge 2101 and the third edge 2201. In the present application, by controlling the first edge 3101 to be located between the second edge 2101 and the third edge 2201, during the charge and discharge process, the electrode assembly 200 expands, the first filling layer 310 can promote higher interface affinity, more complete interface reaction, and alleviate the lithium precipitation phenomenon of the cylindrical secondary battery, which is conducive to improving the cycle performance of the cylindrical secondary battery. After the electrode assembly 200 is cycled, the negative electrode sheet 220 in the negative overhang region has the risk of collapse, and after the negative electrode sheet 220 collapses, there is a risk of contacting the positive electrode sheet 210; the first edge 3101 is controlled to be located between the second edge 2101 and the third edge 2201, and after the electrode assembly 200 is cyclically expanded, the positive electrode sheet 210 can be squeezed on the first filling layer 310, so that if the negative electrode sheet 220 collapses, it will also contact the first filling layer 310, based on the insulation of the first filling layer 310, thereby reducing the risk of the negative electrode sheet 220 contacting the positive electrode sheet 210 and reducing the risk of short circuit; at the same time, the first filling layer 310 has good coating, which can make the overall temperature distribution of the electrode assembly 200 uniform, reduce the side reactions at the corners of the electrode assembly 200, and reduce the risk of lithium deposition at the corners of the electrode assembly 200, thereby improving the safety performance of the cylindrical secondary battery. In this application, the corner refers to the curved part of the electrode assembly 200.

[0046] In some embodiments, along the Z direction, the size of the positive electrode active material layer 2110 is smaller than the size of the first filling layer 310 and smaller than the size of the negative electrode active material layer 2210 .

[0047] In some embodiments, such as Figures 1 to 4As shown, the cylindrical secondary battery is a square shell battery, and the side wall 110 includes a first side wall 111, a second side wall 112, a third side wall 113 and a fourth side wall 114. The first side wall 111 connects the second side wall 112 and the fourth side wall 114, and the third side wall 113 connects the second side wall 112 and the fourth side wall 114. The first side wall 111 and the third side wall 113 are arranged along a first direction, the first direction is the X direction in the figure, that is, the thickness direction of the electrode assembly 200, and the second side wall 112 and the fourth side wall 114 are arranged along a second direction, the second direction is the Y direction in the figure, that is, the length direction of the electrode assembly 200. The size of the first side wall 111 along the second direction is greater than the size of the second side wall 112 along the first direction. The first filling layer 310 includes a first part 311, a second part 312, a third part 313 and a fourth part 314; along the first direction, the first part 311 is arranged between the first side wall 111 and the electrode assembly 200, and the third part 313 is arranged between the electrode assembly 200 and the third side wall 113; along the second direction, the second part 312 is arranged between the second side wall 112 and the electrode assembly 200, and the fourth part 314 is arranged between the electrode assembly 200 and the fourth side wall 114.

[0048] In some embodiments, the cylindrical secondary battery includes N electrode assemblies, N ≥ 2, and along the first direction, the electrode assemblies include a first electrode assembly, a second electrode assembly, ... an N-1th electrode assembly, and an Nth electrode assembly in sequence, the first portion is disposed between the first side wall and the first electrode assembly, and the third portion is disposed between the Nth electrode assembly and the third side wall. In some embodiments, as Figure 5 As shown, the electrode assembly 200 includes a first electrode assembly 201 and a second electrode assembly 202 . Along the first direction X, the first portion 311 is disposed between the first sidewall 111 and the first electrode assembly 201 , and the third portion 313 is disposed between the second electrode assembly 202 and the third sidewall 113 .

[0049] In some embodiments, along the first direction, the thickness of the first part 311 is H11mm, the thickness of the electrode assembly 200 is H0mm, and 0.015≤H11 / H0≤0.03. For example, the value of H11 / H0 can be 0.015, 0.016, 0.017, 0.018, 0.02, 0.022, 0.023, 0.025, 0.026, 0.028, 0.03 or a range consisting of any two of the values. The present application regulates the value of H11 / H0 within the above range so that the first part 311 has a good ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and can also enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0050] In the present application, the thickness of the first portion 311 and the thickness of the third portion 313 may be the same or different; preferably, the thickness of the first portion 311 and the thickness of the third portion 313 are the same.

[0051] In some embodiments, along the first direction, the thickness of the third portion 313 is H13mm, the thickness of the electrode assembly 200 is H0mm, and 0.015≤H13 / H0≤0.03. For example, the value of H13 / H0 can be 0.015, 0.016, 0.017, 0.018, 0.02, 0.022, 0.023, 0.025, 0.026, 0.028, 0.03, or a range consisting of any two of these values. The present application regulates the value of H13 / H0 within the above range so that the third portion 313 has a good ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly 200 during the charge and discharge process, and can also enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0052] In some embodiments, along the first direction, the thickness of the first portion 311 is H11mm, the thickness of the third portion 313 is H13mm, the thickness of the electrode assembly 200 is H0mm, 0.015≤H11 / H0≤0.03, 0.015≤H13 / H0≤0.03. The present application adjusts the values ​​of H11 / H0 and H13 / H0 within the above range, so that the first portion 311 and the third portion 313 have better ability to absorb and store electrolyte, better absorb the expansion force of the electrode assembly 200 during the charge and discharge process, and further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0053] In some embodiments, 0.45≤H11≤2.1. For example, the value of H11 can be 0.45, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.1 or a range consisting of any two of these values. The present application can make the first part 311 have better liquid absorption capacity and better absorb the expansion force of the electrode assembly 200 during the charging and discharging process by regulating the values ​​of H11 / H0 and H11 within the scope of the present application, and can further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0054] In some embodiments, 0.45≤H13≤2.1. For example, the value of H13 can be 0.45, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.1 or a range consisting of any two of these values. The present application can make the third part 313 have better liquid absorption capacity and better absorb the expansion force of the electrode assembly 200 during the charging and discharging process by regulating the values ​​of H13 / H0 and H13 within the scope of the present application, and can further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0055] In some embodiments, 0.45≤H11≤2.1, 0.45≤H13≤2.1. By adjusting the values ​​of H11 / H0 and H11, H13 / H0 and thickness H13 within the scope of the present application, the first portion 311 and the third portion 313 can have better liquid absorption capabilities, better absorb the expansion force of the electrode assembly 200 during the charge and discharge process, and further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, while taking into account the energy density of the cylindrical secondary battery.

[0056] In some embodiments, the thickness of the electrode assembly 200 is H0 mm, 22 ≤ H0 ≤ 105. By regulating H0 and H11 / H0 within the scope of the present application, the first filling layer 310 can better absorb the expansion force of the electrode assembly 200 during the charge and discharge process and exert better liquid absorption capacity, and at the same time, the infiltration effect of the electrolyte in the electrode assembly 200 can be further improved, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0057] In some embodiments, along the second direction, the thickness of the second portion 312 is H12 mm, and 0.33≤H12 / H11≤1. For example, the value of H12 / H11 can be 0.33, 0.34, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range consisting of any two of the values. The expansion force of the cylindrical secondary battery along the first direction X is usually higher than the expansion force along the second direction Y. The present application can better alleviate the expansion of the cylindrical secondary battery along the first direction X by adjusting the thickness of the second part 312 and the thickness ratio H12 / H11 of the first part 311 within the above range, and can better exert the ability of the filling layer 300 to absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and can further reduce the risk of lithium deposition at the corner of the electrode assembly 200, thereby further improving the safety performance of the cylindrical secondary battery. At the same time, the first part 311 and the second part 312 can better absorb and store the electrolyte, and make the electrolyte have a better infiltration effect in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0058] In the present application, the thickness of the second portion 312 and the thickness of the fourth portion 314 may be the same or different; preferably, the thickness of the second portion 312 and the thickness of the fourth portion 314 are the same.

[0059] In some embodiments, along the second direction, the thickness of the fourth portion 314 is H14 mm, and 0.33≤H14 / H11≤1. For example, the value of H14 / H11 can be 0.33, 0.34, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, or a range consisting of any two of the values. The expansion force of the cylindrical secondary battery along the first direction X is usually higher than the expansion force along the second direction Y. The present application can better alleviate the expansion of the cylindrical secondary battery along the first direction X by adjusting the thickness of the fourth part 314 and the thickness ratio H14 / H11 of the first part 311 within the above range, and can better exert the ability of the filling layer 300 to absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and can further reduce the risk of lithium deposition at the corner of the electrode assembly 200, thereby further improving the safety performance of the cylindrical secondary battery. At the same time, the first part 311 and the fourth part 314 can better absorb and store the electrolyte, and make the electrolyte have a better infiltration effect in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0060] In some embodiments, 0.15≤H12≤1.5. For example, the value of H12 can be 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of these values. The present application regulates the values ​​of H12 / H11 and H12 within the scope of the present application, which is conducive to further reducing the risk of lithium deposition at the corners of the electrode assembly 200 and improving the safety performance of the cylindrical secondary battery; at the same time, the first part 311 and the second part 312 can better absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and have better liquid absorption capacity, and can further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the safety performance and cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0061] In some embodiments, 0.15≤H14≤1.5. For example, the value of H14 can be 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of these values. The present application regulates the values ​​of H14 / H11 and H14 within the scope of the present application, which is conducive to further reducing the risk of lithium deposition at the corners of the electrode assembly 200 and improving the safety performance of the cylindrical secondary battery; at the same time, the first part 311 and the second part 312 can better absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and have better liquid absorption capacity, and can further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the safety performance and cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0062] In some embodiments, the thickness of the second filling layer 320 is H21 mm, 0.5≤H21 / H11≤1. For example, the value of H21 / H11 can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or a range consisting of any two of these values. By adjusting the value of H21 / H11 within the above range, the second filling layer 320 can more effectively reduce the risk of damage to the cylindrical secondary battery due to shock or falling, and make the cylindrical secondary battery have better anti-deformation and anti-fall capabilities. At the same time, the first part 311 can better absorb the expansion force of the electrode assembly 200 during the charging and discharging process, thereby further improving the safety performance of the cylindrical secondary battery. The second filling layer 320 and the first filling layer 310 can also have better liquid absorption capacity, which is beneficial to improve the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0063] In some embodiments, 0.23≤H21≤1.5. For example, the value of H21 can be 0.23, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of these values. By adjusting the value of H21 within the above range, the second filling layer 320 can further reduce the risk of damage to the cylindrical secondary battery during shock or fall, further improve the deformation resistance and fall resistance of the cylindrical secondary battery, and thus further improve the safety performance of the cylindrical secondary battery. At the same time, the second filling layer 320 can exert a better liquid absorption ability, which is conducive to improving the wetting effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0064] In some embodiments, the cylindrical secondary battery is a cylindrical battery, such as Figure 6 to Figure 7 As shown, along the radial direction (diameter direction) of the cylindrical battery, such as the X direction in the figure, the thickness of the first filling layer 310 is H10mm, the diameter of the electrode assembly 200 is Dmm, and 0.02≤H10 / D≤0.04. For example, the value of H10 / D can be 0.02, 0.023, 0.025, 0.028, 0.03, 0.032, 0.035, 0.038, 0.04 or a range consisting of any two of these values. By regulating the value of H10 / D within the above range, the present application can enable the first filling layer 310 to have a better ability to absorb and store electrolyte, and can effectively absorb the expansion force of the electrode assembly 200 during the charging and discharging process, and can also improve the infiltration effect of the electrolyte in the electrode assembly 200, thereby improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0065] In some embodiments, 15≤D≤65. For example, the value of D can be 15, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 43, 45, 48, 50, 52, 55, 58, 60, 63, 65, or a range consisting of any two of these values. The present application can make the first filling layer 310 have better liquid absorption capacity and better absorb the expansion force of the electrode assembly 200 during the charging and discharging process by adjusting the value of D within the above range, and can further enhance the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0066] In some embodiments, 0.15≤H10≤2.1. By adjusting H10 / D and H10 within the scope of the present application, the first filling layer 310 can better absorb the expansion force of the electrode assembly 200 during the charge and discharge process and exert better liquid absorption capacity, and at the same time, the infiltration effect of the electrolyte in the electrode assembly 200 can be further improved, thereby further improving the cycle performance and safety performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0067] In some embodiments, the thickness of the second filling layer 320 is H20 mm, and 0.33≤H20 / H10≤1. For example, the value of H20 can be 0.33, 0.34, 0.35, 0.38, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.55, 0.58, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or a range consisting of any two of the values. The present application can make the second filling layer 320 more effectively reduce the risk of damage to the cylindrical secondary battery during shock or fall by regulating the value of H20 / H10 within the above range, so that the cylindrical secondary battery has better anti-deformation and anti-fall capabilities, and at the same time, the first filling layer 310 has better absorption of the expansion force of the electrode assembly 200 during the charging and discharging process, thereby further improving the safety performance of the cylindrical secondary battery. The second filling layer 320 and the first filling layer 310 can also simultaneously exert better liquid absorption capabilities, which is beneficial to improving the infiltration effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0068] In some embodiments, 0.1≤H20≤1.5. For example, the value of H20 can be 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 or a range consisting of any two of these values. By adjusting the value of H20 within the above range, the second filling layer 320 can further reduce the risk of damage to the cylindrical secondary battery during shock or fall, further improve the ability of the cylindrical secondary battery to resist deformation and fall, and thus further improve the safety performance of the cylindrical secondary battery. At the same time, the second filling layer 320 can exert a better liquid absorption ability, which is conducive to improving the wetting effect of the electrolyte in the electrode assembly 200, thereby further improving the cycle performance of the cylindrical secondary battery and taking into account the energy density of the cylindrical secondary battery.

[0069] In some embodiments, the average pore size of the filling layer is dμm, 25≤d≤35. For example, the value of d can be 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or a range consisting of any two of the values. The present application does not particularly limit the source of the materials of the filling layers with different average pore sizes, as long as the purpose of the present application can be achieved. For example, filling layers with different average pore sizes can be purchased. The present application can make the filling layer have better mechanical strength and buffering performance by regulating the value of the average pore size d of the filling layer within the above range, and at the same time, it is beneficial to the absorption and release of the electrolyte, so that the filling layer has a better ability to dynamically release the electrolyte, and the electrolyte can be evenly distributed, which is conducive to improving the wetting effect of the electrolyte in the electrode assembly, so that the filling layer can take into account the liquid absorption capacity, mechanical properties and safety performance at the same time, so that the cylindrical secondary battery has better energy density, cycle performance and safety performance.

[0070] In some embodiments, the porosity of the filling layer is P%, 55≤P≤65. For example, the value of P can be 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65 or a range consisting of any two of the values. The present application does not particularly limit the source of the materials for the filling layers of different porosities, as long as the purpose of the present application can be achieved. For example, filling layers of different porosities can be obtained by purchase. The present application can make the filling layer have good mechanical strength and buffering performance by regulating the value of the porosity P of the filling layer within the above range, and at the same time, it is beneficial to the absorption and release of the electrolyte, so that the filling layer has a good ability to dynamically release the electrolyte, and the electrolyte can be evenly distributed, which is conducive to improving the wetting effect of the electrolyte in the electrode assembly, so that the filling layer can take into account the liquid absorption capacity, mechanical properties and safety performance at the same time, so that the cylindrical secondary battery has good energy density, cycle performance and safety performance.

[0071] In some embodiments, the compression rate of the filling layer is Y%, 35≤Y≤45. For example, the value of Y can be 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45 or a range consisting of any two of these values. The present application does not particularly limit the source of the materials for the filling layers with different compression rates, as long as the purpose of the present application can be achieved. For example, filling layers with different compression rates can be obtained by purchase. The present application can make the filling layer have better mechanical strength by regulating the compression rate of the filling layer within the above range, and can improve the filling layer's ability to absorb the expansion force of the electrode assembly during the charging and discharging process, play a good buffering effect, reduce the risk of shell deformation, and enable the filling layer to maintain its pore structure in a compressed state, which can improve the ability of the electrolyte to be dynamically released, which is beneficial to improving the wettability of the electrolyte in the electrode assembly, thereby improving the safety performance and cycle performance of the cylindrical secondary battery, and taking into account the energy density of the cylindrical secondary battery.

[0072] In some embodiments, the elastic porous insulating material includes at least one of ethylene-vinyl acetate copolymer, polystyrene, polyvinyl chloride, polyacrylic acid, polyvinyl alcohol, polyurethane or polyethylene terephthalate. The above elastic porous insulating material has good elastic deformation properties, heat insulation properties, flame retardant properties, and electrolyte corrosion resistance. The present application adopts the above-mentioned types of elastic porous insulating materials, which can improve the filling layer's ability to absorb the expansion force of the electrode assembly during the charging and discharging process, and can also improve the thermal insulation and flame retardant properties of the cylindrical secondary battery. At the same time, it can improve the liquid absorption capacity of the filling layer, and make the filling layer have a good ability to dynamically release the electrolyte, so that the cylindrical secondary battery can have good energy density, cycle performance and safety performance at the same time.

[0073] In the present application, the negative electrode sheet 220 also includes a negative electrode current collector 2220, and the negative electrode active material layer 2210 is disposed on at least one surface of the negative electrode current collector 2220. The above-mentioned "the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode active material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or on two surfaces of the negative electrode current collector along its own thickness direction. 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.

[0074] The present application has no particular limitation on the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or a composite current collector. For example, the composite current collector may be 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.

[0075] The negative electrode active material layer includes a negative electrode active material. The present application has no particular limitation on the negative electrode active material as long as the purpose of the present application can be achieved. For example, the negative electrode active material may include but is not limited to natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel-structured lithiated TiO 2 -Li 4 Ti 5 O 12 Or at least one of Li-Al alloy.

[0076] In some embodiments, the negative electrode active material layer may also include a conductive agent and a binder. The present application does not particularly limit the types of conductive agents and binders, 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, graphene, metal materials or conductive polymers, and the conductive carbon black may include but is not limited to at least one of acetylene black or Ketjen black. 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 powders and / or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. For example, the binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material layer, and those skilled in the art may select according to actual needs, as long as the purpose of the present application can be achieved.

[0077] In some embodiments, the negative electrode active material layer may further include a conductive agent, a binder and a thickener. The present application does not particularly limit the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, the conductive agent and the binder may be at least one of the above conductive agent and the above binder. The thickener may include but is not limited to at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose. The present application does not particularly limit the mass ratio of the negative electrode active material, the conductive agent, the binder and the thickener in the negative electrode active material layer. Those skilled in the art can choose according to actual needs, as long as the purpose of the present application can be achieved.

[0078] The present application has no particular limitation on the thickness of the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode active material layer is 30 μm to 120 μm.

[0079] The present application has no particular limitation on the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 15 μm.

[0080] Optionally, the negative electrode plate may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode active material layer. The present application has no particular restrictions on the composition of the conductive layer, which may be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive agent and a binder. The present application has no particular restrictions on the conductive agent and the binder in the conductive layer, which may be, for example, at least one of the above conductive agent and the above binder.

[0081] In the present application, the positive electrode sheet 210 includes a positive current collector 2120, and the positive active material layer 2110 is disposed on at least one surface of the positive current collector 2120. The above-mentioned "positive active material layer is disposed on at least one surface of the positive current collector" means that the positive active material layer can be disposed on one surface of the positive current collector along its own thickness direction, or on two surfaces of the positive current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive current collector, or it can be a partial area of ​​the surface of the positive current collector. This application has no special restrictions, as long as the purpose of this application can be achieved.

[0082] The present application has no particular limitation on the positive electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include aluminum foil, aluminum alloy foil or a composite current collector (such as an aluminum-carbon composite current collector).

[0083] The positive electrode active material layer includes a positive electrode active material. The present application has no particular limitation on the positive electrode active material as long as the purpose of the present application can be achieved. For example, the positive electrode active material may include but is not limited to lithium nickel cobalt manganese oxide (such as NCM811, NCM622, NCM523, NCM111), lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO 2 ), at least one of lithium manganese oxide, lithium iron manganese phosphate or lithium titanate.

[0084] The positive electrode active material layer may also include a conductive agent and a binder. The present application has no particular restrictions on the types of the conductive agent and the binder, as long as the purpose of the present application can be achieved. For example, it may be at least one of the above conductive agent and the above binder. The present application has no particular restrictions on the mass ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode active material layer. Those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0085] The thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, and the thickness of the positive electrode active material layer is 30 μm to 120 μm.

[0086] Optionally, the positive electrode sheet may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited, and it can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The present application does not particularly limit the conductive agent and the binder in the conductive layer, for example, it can be at least one of the above conductive agent and the above binder.

[0087] In the present application, there is no particular limitation 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 (e.g., polyethylene terephthalate (PET) films), cellulose, polyimide (PI), polyamide (PA), spandex or aramid. The type of diaphragm may include at least one of a woven membrane, a nonwoven membrane, a microporous membrane, a composite membrane, a rolled membrane or a spun membrane.

[0088] In some embodiments, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used.

[0089] Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic layer.

[0090] In some embodiments, the inorganic layer includes inorganic particles and a binder. The application is not particularly limited to inorganic particles, such as inorganic particles can include at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate. The application is not particularly limited to binders, such as binders can be at least one of the above-mentioned binders. In some embodiments, the polymer layer includes polymers, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymers, polyacrylic acid, polyacrylates, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

[0091] In the present application, there is no particular limitation on the thickness of the separator as long as the purpose of the present application can be achieved. For example, the thickness of the separator may be 3 μm to 30 μm.

[0092] In the present application, the cylindrical secondary battery further includes an electrolyte including a lithium salt and a non-aqueous solvent.

[0093] The present application has no particular restrictions on lithium salts, as long as the purpose of the present application can be achieved. For example, lithium salts may include but are not limited to LiPF 6 , LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 , Li 2 SiF 6 At least one of lithium bis(oxalatoborate) (LiBOB) or lithium difluoroborate. The present application has no particular limitation on the content of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved.

[0094] The present application has no particular limitation 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 carbonate compounds, carboxylate compounds, ether compounds or other organic solvents.

[0095] The carbonate compound may include but is not limited to at least one of a linear carbonate compound, a cyclic carbonate compound or a fluorinated carbonate compound. The linear carbonate compound may include but is not limited to at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC) or methyl ethyl carbonate (MEC). The cyclic carbonate may include but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) or vinyl ethylene carbonate (VEC). The fluorinated carbonate compound may include, but is not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The above-mentioned 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, decalactone, valerolactone, or caprolactone. The above-mentioned 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 above-mentioned other organic solvents may include but are not limited to at least one of dimethyl sulfoxide, 1,2-dioxolane, cyclopentane, methyl cyclopentane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate or trioctyl phosphate. The present application has no particular restrictions on the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0096] In the present application, the shell is used to accommodate the positive electrode plate, the diaphragm, the negative electrode plate and the electrolyte, as well as other components known in the field of secondary batteries, and the present application does not limit the above-mentioned other components. The present application has no special restrictions on the shell, and it can be a shell known in the art, as long as the purpose of the present application can be achieved. For example, the shell can be a hard shell or a flexible shell. The material of the hard shell can be metal, and the present application does not limit the type of metal. A metal hard shell known in the art can be used, as long as the purpose of the present application can be achieved. The flexible shell can be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0097] In the present application, the cylindrical secondary battery further includes a top cover, which covers the top of the shell and together defines a receiving space for receiving the electrode assembly.

[0098] The present application has no particular restrictions on the preparation process of the cylindrical secondary battery. For example, the preparation process of the cylindrical secondary battery may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in order, and winding, folding and other operations as needed to obtain an electrode assembly of a winding structure, setting a second filling layer on the bottom surface of the electrode assembly, setting a first filling layer on the side surface of the electrode assembly, and then placing the electrode assembly in a shell, injecting the electrolyte into the shell and sealing it to obtain a cylindrical secondary battery. Alternatively, stack the positive electrode sheet, the separator and the negative electrode sheet in order, and then fix the four corners of the entire stacked structure with tape to obtain an electrode assembly of a stacked structure, setting a second filling layer on the bottom surface of the electrode assembly, setting a first filling layer on the side surface of the electrode assembly, and then placing the electrode assembly in the shell, injecting the electrolyte into the shell and sealing it to obtain a cylindrical secondary battery. In some embodiments, the cylindrical secondary battery is a cylindrical battery, and the electrode assembly can form a cylindrical structure with a central hole after winding. In addition, overcurrent protection elements, guide plates, etc. may be placed in the housing as needed to prevent pressure rise and overcharge and discharge inside the cylindrical secondary battery. In the present application, the first filling layer and the second filling layer are connected to each other, and the first filling layer and the second filling layer are connected as a whole and arranged between the housing and the electrode assembly; or the first filling layer and the second filling layer are arranged separately, and the intersection is tightly fitted, so that the first filling layer and the second filling layer are connected.

[0099] The second aspect of the present application provides an electric device, which includes the cylindrical secondary battery provided in the first aspect of the present application. The cylindrical secondary battery of the present application has high energy density, good cycle performance and safety performance, so the electric device of the present application has a long service life.

[0100] The application does not particularly limit the type of electrical device, and it can be used for any electrical device known in the prior art. In some embodiments, the electrical device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, a liquid crystal 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, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0101] Example

[0102] Hereinafter, embodiments and comparative examples are given to explain the implementation methods of the present application in more detail. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are weight references. It should be noted that in the embodiments of the present application, lithium-ion batteries are used as examples of cylindrical secondary batteries to explain the present application, but the cylindrical secondary batteries of the present application are not limited to lithium-ion batteries.

[0103] Test methods and equipment:

[0104] Energy density test:

[0105] Place the lithium-ion battery in a 25℃±2℃ constant temperature box and let it stand for 30 minutes to allow the lithium-ion battery to reach a constant temperature. Charge the lithium-ion battery that has reached a constant temperature at a constant current of 0.5C to a full charge voltage of 4.5V, then charge it at a full charge voltage of 4.5V to a current of 0.05C, and discharge it at a constant current of 0.2C to a voltage of 3.0V, and record the discharge energy. Energy density (Wh / L) = discharge capacity (Wh) / lithium-ion battery volume size (L). The size parameters of the lithium-ion battery are measured by a micrometer, and each value is measured 3 times, and the average value is taken as the final result.

[0106] Cycle performance test:

[0107] In a 25℃±2℃ constant temperature box, the lithium-ion battery is charged to 4.5V at a constant current of 1.5C, and then charged to 0.05C at a constant voltage of 4.5V, and then stopped to fully charge the lithium-ion battery. It is left to stand for 15 minutes, and then discharged to 2.5V at a constant current of 4C, and left to stand for 30 minutes. This step process is considered as one cycle. According to the above charge and discharge process, the test is cycled for 800 cycles. The discharge capacity of the first cycle is Q 0 , the discharge capacity at the 800th cycle is Q 800 , calculate the cycle capacity retention rate of the lithium-ion battery at the 800th cycle = Q 800 / Q 0 × 100%. The thickness of the lithium-ion battery when it is discharged to 30% SOC (discharged to 3.4V) in the first cycle is T 0 (PPG battery thickness gauge, thickness measurement pressure 50g), test and record the thickness of the fully charged lithium-ion battery at the 800th cycle as T 800 , calculate the cycle expansion rate of the 800th lithium-ion battery = (T 800 -T 0 ) / T 0 ×100%.

[0108] Drop performance test:

[0109] Place the lithium-ion battery in an environment of 25°C, charge it at a constant current of 0.5C to a voltage of 4.5V, then charge it at a constant voltage of 4.5V to a cut-off current of 0.05C, and let it stand for 5 minutes to fully charge it. Place the lithium-ion battery in a fixed fixture, inspect its appearance and take photos before and after the test. Use the fixture to drop it onto the floor from a height of 1.8m, drop it once along the head and tail, and once at the four corners, for a total of 7 rounds of testing, 1 round for 6 times, and the order of dropping is: head, tail, right corner of the head, right corner of the tail, left corner of the head, left corner of the tail (angle: 45 degrees).

[0110] The voltage and internal resistance of the lithium-ion battery are measured before and 24 hours after the drop test. The criteria for passing the drop test are: no fire, no explosion, no smoke, no leakage, and voltage drop <50mV. The voltage drop is measured by placing a universal voltmeter at the pole ear of the lithium-ion battery and reading the voltage value before and 24 hours after the drop test. Voltage drop = voltage value before the drop test - voltage value after the drop test. Twenty lithium-ion batteries are tested for each embodiment or comparative example, and the number of passed batteries is recorded. The drop pass rate (%) = the number of lithium-ion batteries that passed the drop test / the total number of lithium-ion batteries tested × 100%, such as 90% means that 20 lithium-ion batteries were tested and 18 passed the drop test.

[0111] Lithium deposition performance test:

[0112] Place the lithium-ion battery in a constant temperature box at 10°C for 60 minutes, charge it to 4.5V at 2C constant current, charge it to 0.05C at 4.5V constant voltage, let it stand for 5 minutes, and then discharge it to 2.5V at 0.5C constant current. This is one cycle. After 10 cycles of the above charge and discharge process, charge it to 4.5V at 2C constant current, charge it to 0.05C at 4.5V constant voltage, let it stand for 5 minutes, and then disassemble the lithium-ion battery to observe the lithium deposition state on the surface of the negative electrode. The surface area without lithium deposition is golden yellow, and the lithium deposition area is grayish white.

[0113] The criteria for judging the degree of lithium deposition in lithium-ion batteries are as follows: a lithium deposition area of ​​0% means no lithium deposition, i.e., the degree of lithium deposition is none; a lithium deposition area greater than 0 and less than or equal to 2% means mild lithium deposition, i.e., the degree of lithium deposition is mild; a lithium deposition area greater than 2% and less than or equal to 20% means moderate lithium deposition, i.e., the degree of lithium deposition is moderate; a lithium deposition area greater than 20% and less than or equal to 100% means severe lithium deposition, i.e., the degree of lithium deposition is severe, wherein the percentage of the lithium deposition area is calculated based on the surface area of ​​the negative electrode.

[0114] In this application, those skilled in the art will understand that "C" refers to the rated capacity of the finished lithium-ion battery when it leaves the factory. "1C" is the current value that fully discharges the capacity of the lithium-ion battery within 1 hour, "0.1C" is the current value that fully discharges the capacity of the lithium-ion battery within 10 hours, and other multiples are similar.

[0115] Example 1-1

[0116] <Preparation of positive electrode sheet>

[0117] The positive electrode active material is lithium cobalt oxide (LiCoO 2 ), conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97.9:0.9:1.2, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and the positive electrode slurry is obtained after vacuum stirring. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 120°C to obtain a positive electrode sheet with a single-sided coating of a positive electrode active material layer. The coating weight of the positive electrode active material layer is 267.8mg / 1540mm 2 Then repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. Dry at 120°C and then cold press, and then cut into pieces to obtain a positive electrode sheet with a specification of 74mm×867mm for standby use. The thickness of the single-sided positive electrode active material layer is 42μm.

[0118] <Preparation of negative electrode sheet>

[0119] The negative electrode active material artificial graphite, the binder styrene butadiene rubber, and the conductive agent acetylene black were mixed in a mass ratio of 97.4:1.4:1.2, and deionized water was added as a solvent to prepare a slurry with a solid content of 45wt%. The negative electrode slurry was obtained after being stirred evenly by a vacuum mixer. The negative electrode slurry was evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm, and dried at 120°C to obtain a negative electrode sheet with a negative electrode active material layer coated on one side. The coating weight of the negative electrode active material layer was 142mg / 1540mm 2 Then repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. After drying at 120°C, cold pressing and cutting, a negative electrode sheet with a specification of 78mm×875mm is obtained for standby use. The thickness of the single-sided negative electrode active material layer is 54.5μm.

[0120] <Preparation of Electrolyte>

[0121] In an argon atmosphere glove box with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 1:1:1, and then lithium salt lithium hexafluorophosphate (LiPF 6 ) are mixed evenly to obtain an electrolyte. Based on the mass of the electrolyte, the lithium salt LiPF 6 The mass percentage is 12.5%, and the balance is non-aqueous organic solvent.

[0122] <Diaphragm>

[0123] A polyethylene (PE) porous membrane with a thickness of 7 μm (provided by Shanghai Enjie Company) was used as the separator.

[0124] <Preparation of square-shell lithium-ion batteries>

[0125] The positive electrode sheet, separator, and negative electrode sheet prepared above are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain a square electrode assembly with a thickness of H0mm of 45mm and dimensions of length 155mm×width 45mm×height 78mm.

[0126] Set up the second filling layer: coat the bottom surface of the electrode assembly with an elastic porous insulating material polystyrene film with a thickness of H21mm and a length of 0.63mm, a length of 156mm and a width of 46.8mm (number average molecular weight of 6000, average pore size dμm of 30μm, porosity P% of 60%, compression rate Y% of 40%) as the second filling layer, and fix it with acrylic green glue while coating.

[0127] Set the first fill layer: Figures 1 to 4 As shown, the thickness direction of the electrode assembly is the X direction, the length direction is the Y direction, and the height direction is the Z direction; the surfaces on both sides of the electrode assembly in the X direction are coated with a 0.90mm thick elastic porous insulating material polystyrene film, and the surfaces on both sides of the electrode assembly in the Y direction are coated with a 0.50mm thick elastic porous insulating material polystyrene film as the first filling layer, which is coated and fixed with acrylic green glue at the same time, wherein the thickness (X direction) of the first part of the first filling layer H11mm is 0.90mm, and the size in the Y direction is 156mm, the thickness (X direction) of the third part H13mm is 0.90mm, and the size in the Y direction is 156mm, the thickness (Y direction) of the second part H12mm is 0.50mm, and the size in the X direction is 45mm, and the thickness (Y direction) of the fourth part H14mm is 0.50mm, and the size in the X direction is 45mm.

[0128] Along the Z direction, the top edge of the first filling layer is the first edge, the top edge of the positive electrode active material layer in the positive electrode sheet is the second edge, and the top edge of the negative electrode active material layer in the negative electrode sheet is the third edge. The size of the first filling layer in the Z direction is 75 mm, so that the first edge is located between the second edge and the third edge. The second filling layer is connected to the first filling layer to completely cover the side surface and the bottom surface of the electrode assembly.

[0129] After welding the pole ears, the electrode assembly is loaded into the aluminum-plastic film of the square shell outer packaging, placed in a vacuum oven at 85°C for 12 hours to remove moisture, injected with the above-mentioned electrolyte, and subjected to vacuum packaging, standing, formation (the formation upper limit voltage is 4.5V, the formation temperature is 70°C, and the formation standing time is 2h), shaping, capacity testing and other processes to obtain a square shell lithium-ion battery.

[0130] Example 1-2 to Example 1-30

[0131] Except for adjusting the corresponding preparation parameters according to Table 1 in <Preparation of Square Shell Lithium Ion Battery>, and adaptively adjusting the Y-direction dimensions of the first and third parts, the X-direction dimensions of the second and fourth parts, and the length and width of the second filling layer, the rest are the same as Example 1-1, wherein the Y-direction dimension of the first or third part (mm) = 155mm + H12mm + H14mm, the X-direction dimension of the second or fourth part (mm) = H0mm, the length of the second filling layer (mm) = 155mm + H12mm + H14mm, and the width of the second filling layer (mm) = H0mm + H11mm + H13mm.

[0132] Example 2-1

[0133] <Preparation of positive electrode sheet>, <Preparation of negative electrode sheet>, <Preparation of electrolyte>, and <Separator> are the same as in Example 1-1.

[0134] <Preparation of cylindrical lithium-ion batteries>

[0135] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain a cylindrical electrode assembly with a diameter Dmm of 27mm and a height of 78mm.

[0136] Set up the second filling layer: coat the bottom surface of the electrode assembly with an elastic porous insulating material polystyrene film with a thickness of 0.30mm and a diameter of 28.60mm (number average molecular weight of 6000, average pore size dμm of 30μm, porosity P% of 60%, compression rate Y% of 40%) as the second filling layer, and fix it with acrylic green glue while coating.

[0137] Set the first fill layer: Figure 6 to Figure 7As shown, a polystyrene film of elastic porous insulating material with a thickness of H10mm and 0.80mm is coated on the side surface of the electrode assembly as the first filling layer, and is fixed with acrylic green glue while coating. In the height direction, the top edge of the first filling layer is the first edge, the top edge of the positive electrode active material layer in the positive electrode sheet is the second edge, and the top edge of the negative electrode active material layer in the negative electrode sheet is the third edge. The size of the first filling layer in the height direction is 75mm, so that the first edge is located between the second edge and the third edge. The second filling layer is connected to the first filling layer to completely cover the side surface and bottom surface of the electrode assembly.

[0138] After welding the tabs, the electrode assembly is placed in a cylindrical outer packaging aluminum-plastic film, placed in a vacuum oven at 85°C for 12 hours to remove moisture, injected with the above-mentioned electrolyte, and subjected to vacuum packaging, standing, formation (the formation upper limit voltage is 4.5V, the formation temperature is 70°C, and the formation standing time is 2h), shaping, capacity testing and other processes to obtain a cylindrical lithium-ion battery.

[0139] Example 2-2 to Example 2-21

[0140] Except for adjusting the corresponding preparation parameters according to Table 2 in <Preparation of Cylindrical Lithium-ion Batteries> and adaptively adjusting the diameter of the second filling layer, the rest is the same as Example 2-1, wherein the diameter of the second filling layer (mm) = Dmm+H10mm+H10mm.

[0141] Example 3-1 to Example 3-9

[0142] Except that in <Preparation of Square Shell Lithium Ion Battery>, different average pore diameters dμm, or different porosities P%, or different compression rates Y%, or different types of elastic porous insulating materials are used according to Table 3, the rest are the same as Example 1-1, wherein the number average molecular weight of polyethylene terephthalate is 30,000.

[0143] Comparative Example 1-1

[0144] Except that the first filling layer and the second filling layer are not provided in the preparation of square-shell lithium-ion battery, the rest is the same as that of Example 1-1.

[0145] Comparative Example 1-2

[0146] Except that only the first filling layer is provided and the second filling layer is not provided in <Preparation of square-shell lithium-ion battery>, the rest is the same as Example 1-1.

[0147] Comparative Examples 1-3

[0148] Except that only the second filling layer is provided in the preparation of square-shell lithium-ion battery and the first filling layer is not provided, the rest is the same as that of Example 1-1.

[0149] Comparative Example 2-1

[0150] Except that the first filling layer and the second filling layer are not provided in <Preparation of Cylindrical Lithium-ion Battery>, the rest is the same as Example 2-1.

[0151] Comparative Example 2-2

[0152] Except that only the first filling layer is provided and the second filling layer is not provided in <Preparation of Cylindrical Lithium-ion Battery>, the rest is the same as Example 2-1.

[0153] Comparative Examples 2-3

[0154] Except that only the second filling layer is provided in the <Preparation of Cylindrical Lithium-ion Battery> and the first filling layer is not provided, the rest is the same as Example 2-1.

[0155]

[0156]

[0157]

[0158] It can be seen from Examples 1-1 to 1-30, Comparative Examples 1-1 to 1-3, Examples 2-1 to 2-21, and Comparative Examples 2-1 to 2-3 that the cylindrical lithium ion battery having the first filling layer and the second filling layer of the present application has a higher energy density, a higher cycle capacity retention rate, a lower cycle expansion rate, a better lithium plating condition, and a higher drop test pass rate, indicating that the cylindrical lithium ion battery of the present application has high energy density, good cycle performance and safety performance.

[0159] The values ​​of H11 / H0, H11, H13 / H0, and H13 usually affect the energy density, cycle performance, and safety performance of square-shell lithium-ion batteries. From Examples 1-1 to 1-10, it can be seen that square-shell lithium-ion batteries using values ​​of H11 / H0, H11, H13 / H0, and H13 within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation, and higher drop test pass rate, indicating that square-shell lithium-ion batteries have higher energy density, better cycle performance, and safety performance.

[0160] The values ​​of H12 / H11, H12, H14 / H11, and H14 usually affect the energy density, cycle performance, and safety performance of square-shell lithium-ion batteries. It can be seen from Example 1-1, Example 1-7 to Example 1-9, and Example 1-11 to Example 1-21 that square-shell lithium-ion batteries using the values ​​of H12 / H11, H12, H14 / H11, and H14 within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation, and higher drop test pass rate, indicating that square-shell lithium-ion batteries have higher energy density, better cycle performance, and safety performance.

[0161] The values ​​of H21 / H11 and H21 usually affect the energy density, cycle performance and safety performance of square shell lithium ion batteries. It can be seen from Examples 1-1, 1-7 to 1-9, 1-19, 1-22 to 1-30 that square shell lithium ion batteries using values ​​of H21 / H11 and H21 within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation and higher drop test pass rate, indicating that square shell lithium ion batteries have higher energy density, better cycle performance and safety performance.

[0162] The values ​​of H10 / D and D usually affect the energy density, cycle performance and safety performance of cylindrical lithium-ion batteries. From Example 2-1 to Example 2-11, it can be seen that the cylindrical lithium-ion batteries using the values ​​of H10 / D and D within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation and higher drop test pass rate, indicating that the cylindrical lithium-ion batteries have higher energy density, better cycle performance and safety performance.

[0163] The values ​​of H20 / H10 and H20 usually affect the energy density, cycle performance and safety performance of cylindrical lithium-ion batteries. It can be seen from Example 2-1, Example 2-7 to Example 2-8, and Example 2-12 to Example 2-21 that cylindrical lithium-ion batteries using H20 / H10 and H20 values ​​within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation and higher drop test pass rate, indicating that cylindrical lithium-ion batteries have higher energy density, better cycle performance and safety performance.

[0164] The average pore size, porosity, and compression ratio of the filling layer usually affect the energy density, cycle performance, and safety performance of the cylindrical lithium-ion battery. It can be seen from Examples 1-1, 3-1, and 3-8 that the cylindrical lithium-ion battery using the average pore size, porosity, and compression ratio of the filling layer within the scope of the present application has a higher energy density, a higher cycle capacity retention rate, a lower cycle expansion rate, a better lithium precipitation situation, and a higher drop test pass rate, indicating that the cylindrical lithium-ion battery has a higher energy density, better cycle performance, and safety performance.

[0165] The type of elastic porous insulating material usually affects the energy density, cycle performance and safety performance of cylindrical lithium-ion batteries. It can be seen from Examples 1-1 and 3-9 that cylindrical lithium-ion batteries using elastic porous insulating materials within the scope of this application have higher energy density, higher cycle capacity retention rate, lower cycle expansion rate, better lithium precipitation and higher drop test pass rate, indicating that cylindrical lithium-ion batteries have higher energy density, better cycle performance and safety performance.

[0166] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method or article.

[0167] The terms "one of", "one of", "a kind of" or other similar terms connected to the elements refer to any one of the listed elements. For example, "one of A or B" means only A or only B; as another example, "one of A, B, and C" means only A, only B, or only C. The terms "at least one of", "at least one of", "at least one of" or other similar terms connected to the elements refer to any combination of the listed elements. For example, "at least one of A or B" means only A, only B, A and B. As another example, "at least one of A, B, or C" means only A, only B, only C, only A and B, only A and C, only B and C, A, B, and C.

[0168] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0169] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A cylindrical secondary battery, characterized in that: include: A housing, comprising a side wall and a bottom wall; An electrode assembly is disposed in the housing; a filling layer, comprising a first filling layer and a second filling layer connected to each other, wherein the first filling layer is located between the electrode assembly and the side wall along the circumference of the side wall, and the second filling layer is located between the electrode assembly and the bottom wall; The filling layer includes an elastic porous insulating material.

2. The cylindrical secondary battery according to claim 1, characterized in that: The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, and the negative electrode sheet comprises a negative electrode active material layer; Along the direction of the bottom wall pointing to the electrode assembly, the edge of the first filling layer away from the bottom wall is the first edge, the edge of the positive electrode active material layer away from the bottom wall is the second edge, and the edge of the negative electrode active material layer away from the bottom wall is the third edge, the third edge is higher than the second edge, and the first edge is located between the second edge and the third edge.

3. The cylindrical secondary battery according to claim 1, characterized in that: The cylindrical secondary battery is a square shell battery, the side wall includes a first side wall, a second side wall, a third side wall and a fourth side wall, the first side wall connects the second side wall and the fourth side wall, the third side wall connects the second side wall and the fourth side wall, the first side wall and the third side wall are arranged along a first direction, the second side wall and the fourth side wall are arranged along a second direction, and the size of the first side wall along the second direction is greater than the size of the second side wall along the first direction; The first filling layer includes a first part, a second part, a third part and a fourth part; along the first direction, the first part is arranged between the first side wall and the electrode assembly, and the third part is arranged between the electrode assembly and the third side wall; along the second direction, the second part is arranged between the second side wall and the electrode assembly, and the fourth part is arranged between the electrode assembly and the fourth side wall; Along the first direction, the thickness of the first portion is H11 mm, the thickness of the electrode assembly is H0 mm, and 0.015≤H11 / H0≤0.03; And / or, along the first direction, the thickness of the third portion is H13 mm, 0.015≤H13 / H0≤0.

03.

4. The cylindrical secondary battery according to claim 3, characterized in that: 0.45≤H11≤2.1; and / or, 0.45≤H13≤2.

1.

5. The cylindrical secondary battery according to claim 3, characterized in that: Along the second direction, the thickness of the second portion is H12 mm, 0.33≤H12 / H11≤1; And / or, along the second direction, the thickness of the fourth portion is H14 mm, and 0.33≤H14 / H11≤1.

6. The cylindrical secondary battery according to claim 5, characterized in that: 0.15≤H12≤1.5; and / or, 0.15≤H14≤1.

5.

7. The cylindrical secondary battery according to claim 3, characterized in that: The thickness of the second filling layer is H21 mm, and 0.5≤H21 / H11≤1.

8. The cylindrical secondary battery according to claim 7, characterized in that: 0.23≤H21≤1.5。 9. The cylindrical secondary battery according to claim 1, characterized in that: The cylindrical secondary battery is a cylindrical battery. Along the radial direction of the cylindrical battery, the thickness of the first filling layer is H10 mm, the diameter of the electrode assembly is D mm, and 0.02≤H10 / D≤0.

04.

10. The cylindrical secondary battery according to claim 9, characterized in that: 15≤D≤65。 11. The cylindrical secondary battery according to claim 9, characterized in that: The thickness of the second filling layer is H20 mm, and 0.33≤H20 / H10≤1.

12. The cylindrical secondary battery according to claim 11, characterized in that: 0.1≤H20≤1.5。 13. The cylindrical secondary battery according to any one of claims 1 to 12, characterized in that: The cylindrical secondary battery satisfies at least one of the following conditions: (1) The average pore size of the filling layer is d μm, 25≤d≤35; (2) The porosity of the filling layer is P%, 55≤P≤65; (3) The compression rate of the filling layer is Y%, 35≤Y≤45.

14. The cylindrical secondary battery according to any one of claims 1 to 13, characterized in that: The elastic porous insulating material includes at least one of ethylene-vinyl acetate copolymer, polystyrene, polyvinyl chloride, polyacrylic acid, polyvinyl alcohol, polyurethane or polyethylene terephthalate. 15 . An electric device comprising the cylindrical secondary battery according to claim 1 .

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