Electrochemical device and electronic device

Abstract

The invention provides an electrochemical device and an electronic device. The electrochemical device comprises a shell and an electrode assembly, the electrode assembly comprises a pole piece assembly accommodated in the shell and a pole lug connected with the pole piece assembly, and the pole lug extends out of the shell along a first direction; in the first direction, the shell comprises a first side wall and a second side wall which are oppositely arranged, the shell further comprises a third side wall and a fourth side wall which are oppositely arranged in the second direction, and a top wall and a bottom wall which are oppositely arranged in the third direction; the first direction, the second direction and the third direction are vertical in pairs; at least one of the third side wall and the fourth side wall is provided with a protruding part protruding in the direction away from the pole piece assembly. According to the electrochemical device, the risk of shell corner damage in the circulation process can be reduced, and the use safety of the electrochemical device is improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Art

[0002] As consumers have higher and higher requirements for the battery life of electronic devices, the requirements for the energy density of lithium-ion batteries are also getting higher and higher. In order to improve the energy density of lithium-ion batteries, it is usually chosen to use heavier coating weights for pole pieces, thinner current collector foils, or use silicon materials for the negative electrode. Summary of the invention

[0003] However, the inventor of this application has found that as the energy density of lithium-ion batteries increases, the corners of the packaging bag are prone to damage during the cycle, resulting in leakage. In view of this, the purpose of this application is to provide an electrochemical device and an electronic device to reduce the risk of failure due to corner damage of the packaging bag during the cycle of the electrochemical device.

[0004] The first aspect of the present application provides an electrochemical device, including a shell and an electrode assembly; the electrode assembly includes a pole piece assembly accommodated in the shell and a pole ear connected to the pole piece assembly, and the pole ear extends out of the shell along a first direction; along the first direction, the shell includes a first side wall and a second side wall arranged opposite to each other, and the shell also includes a third side wall and a fourth side wall arranged opposite to each other along the second direction, and a top wall and a bottom wall arranged opposite to each other along the third direction; the first direction, the second direction and the third direction are perpendicular to each other; at least one of the third side wall and the fourth side wall has a protrusion protruding away from the pole piece assembly.

[0005] The inventor of the present application has found that during the cycle of the electrochemical device, the expansion of the pole piece assembly in the first direction will cause compression on the corner of the shell. At the same time, the expansion of the pole piece assembly in the third direction will pull the shell inward, thereby further increasing the reverse extrusion force of the electrode assembly on the corner of the shell, which in turn causes damage to the corner of the shell and brings safety risks. The present application provides a protrusion on the third side wall and / or the fourth side wall. During the cycle of the electrochemical device, when the pole piece assembly expands along the first direction and squeezes the corner of the shell, the protrusion of the third side wall and / or the fourth side wall can deform to provide a buffer. At the same time, when the pole piece assembly expands along the third direction and pulls the shell, the deformation of the protrusion of the third side wall and / or the fourth side wall can alleviate the pulling on the corner of the shell, thereby helping to reduce the reverse extrusion force on the corner of the shell and reduce the risk of damage to the corner of the shell.

[0006] In some embodiments of the present application, along the second direction, the size of the first side wall is L1, and the electrochemical device satisfies at least one of the following conditions: (1) the third side wall has a first protrusion protruding in a direction away from the pole piece assembly, and along the second direction, the maximum size of the first protrusion is h1, satisfying: h1≤0.1L1; (2) the fourth side wall has a second protrusion protruding in a direction away from the pole piece assembly, and along the second direction, the maximum size of the second protrusion is h2, satisfying: h2≤0.1L1. By controlling the maximum size of the protrusion along the second direction within the above range, the influence of the protrusion on the volume energy density of the electrochemical device can be reduced.

[0007] In some embodiments of the present application, the electrochemical device satisfies at least one of the following conditions: (1) The third side wall has a first protrusion protruding in a direction away from the pole piece assembly, and along the first direction, the size of the third side wall is L3; along the second direction, the maximum size of the first protrusion is h1, and the following conditions are satisfied: h1 ≥ 0.002L3; (2) The fourth side wall has a second protrusion protruding in a direction away from the pole piece assembly, and along the first direction, the size of the fourth side wall is L4; along the second direction, the maximum size of the second protrusion is h2, and the following conditions are satisfied: h2 ≥ 0.002L4. By controlling the maximum size of the protrusion along the second direction within the above range, when the corner of the shell is squeezed, it can better deform to provide a buffer, further reducing the risk of damage to the corner of the shell.

[0008] In some embodiments of the present application, the electrochemical device satisfies at least one of the following conditions: (1) along the first direction, the size of the first protrusion is w1, satisfying 0.1L3≤w1≤L3; (2) along the first direction, the size of the second protrusion is w2, satisfying 0.1L4≤w2≤L4. By controlling the size of the protrusion along the first direction within the above range, the protrusion can meet the expansion requirements of the pole piece assembly through a small amount of deformation, thereby more quickly relieving the extrusion of the shell corners and further reducing the risk of shell corner damage.

[0009] In some embodiments of the present application, the protrusion is arc-shaped. Thus, on the one hand, the arc-shaped protrusion is easier to deform and extend, and can deform more quickly when squeezed and pulled to relieve the squeezing of the shell corners, thereby further reducing the risk of shell corner damage. On the other hand, the arc shape is easy to process, and the deformation requirements of the third side wall and / or the fourth side wall are relatively small, so that the structural strength of the third side wall and / or the fourth side wall can be maintained.

[0010] In some embodiments of the present application, the electrochemical device satisfies at least one of the following conditions: (1) the third side wall has a plurality of first protrusions protruding in a direction away from the pole piece assembly; (2) the fourth side wall has a plurality of second protrusions protruding in a direction away from the pole piece assembly. The provision of a plurality of protrusions can increase the deformability of the side wall, thereby better relieving the extrusion of the corner of the shell, and further reducing the risk of damage to the corner of the shell.

[0011] In some embodiments of the present application, the electrochemical device satisfies at least one of the following conditions: (1) the number of the first protrusions is n1, 2≤n1≤5; (2) the number of the second protrusions is n2, 2≤n2≤5.

[0012] In some embodiments of the present application, the electrochemical device satisfies at least one of the following conditions: (1) the bottom wall includes a first region and a second region, and when viewed along the third direction, the pole piece assembly covers the first region, and the second region exceeds the pole piece assembly and is connected to the protrusion; (2) the top wall includes a third region and a fourth region, and when viewed along the third direction, the pole piece assembly covers the third region, and the fourth region exceeds the pole piece assembly and is connected to the protrusion. When the pole piece assembly expands and pulls the shell along the third direction, the second region and / or the fourth region can reduce the pulling on the corner of the shell by deformation, thereby facilitating further reducing the reverse extrusion force on the corner of the shell and reducing the risk of damage to the corner of the shell.

[0013] In some embodiments of the present application, the top wall and / or bottom wall of the electrochemical device is in any of a square, a trapezoid or an L-shape.

[0014] A second aspect of the present application provides an electronic device, which includes the electrochemical device provided by the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other embodiments based on these drawings.

[0016] Figure 1 A schematic diagram of the structure of an electrochemical device according to an embodiment of the present application;

[0017] Figure 2 for Figure 1 A side view of the electrochemical device structure shown;

[0018] Figure 3 A schematic diagram of the structure of an electrochemical device according to another embodiment of the present application;

[0019] Figure 4A schematic diagram of the structure of an electrochemical device according to a third embodiment of the present application;

[0020] Figure 5 A schematic diagram of the structure of an electrochemical device according to a fourth embodiment of the present application;

[0021] Figure 6 This is a schematic diagram of the structure of an electrochemical device according to the fifth embodiment of the present application.

[0022] Reference numerals: first side wall 101 ; second side wall 102 ; bottom wall 103 ; top wall 104 ; first protrusion 105 ; second protrusion 106 ; third side wall 107 ; fourth side wall 108 ; sealing portion 109 ; pole ear 110 ; first region 111 ; second region 112 ; third region 113 ; fourth region 114 . DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0024] It should be noted that when an element is described as "connected" to another element, it can be directly connected to another element, or there can be one or more intermediate elements therebetween. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by technicians in the technical field of this application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not used to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more related listed items.

[0025] The inventor of this application has found that as the energy density of lithium-ion batteries increases, the corners of the packaging bag are prone to damage during the cycle, leading to leakage. The study found that this is because the expansion of the pole piece during the cycle is significantly aggravated. On the one hand, the expansion of the pole piece in the width direction increases significantly, constantly squeezing the corners of the packaging bag; on the other hand, the expansion of the pole piece in the thickness direction further pulls the packaging bag inward, further increasing the reverse squeezing force on the corners of the packaging bag, causing the corners of the packaging bag to be damaged and the battery to fail.

[0026] In view of this, the first aspect of the present application provides an electrochemical device, including a shell and an electrode assembly; the electrode assembly includes a pole piece assembly housed in the shell and a pole ear connected to the pole piece assembly, the pole ear extending out of the shell along a first direction; along the first direction, the shell includes a first side wall and a second side wall arranged opposite to each other, the shell also includes a third side wall and a fourth side wall arranged opposite to each other along the second direction, and a top wall and a bottom wall arranged opposite to each other along the third direction; the first direction, the second direction and the third direction are perpendicular to each other; at least one of the third side wall and the fourth side wall has a protrusion protruding away from the pole piece assembly. Figures 1 to 6 As shown in the figure, the Y direction is the third direction, the X direction is the second direction, and the Z direction is the first direction. Figure 2 As shown, the two planes perpendicular to the Y direction are the top wall 104 and the bottom wall 103; the two planes perpendicular to the Z direction are the first side wall 101 and the second side wall 102; and the remaining two side walls are the third side wall 107 and the fourth side wall 108. Figure 1 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the dotted line is the connecting line between the opposite sides of the first side wall 101 and the second side wall 102, which indicates the outer dimensions when the third side wall 107 and / or the fourth side wall 108 are straight side walls. The sealing portion 109 is a part of the housing, and the tab 110 extends out of the housing from the sealing portion 109. By providing the first protrusion 105 and / or the second protrusion 106 on the third side wall 107 and / or the fourth side wall 108, during the cycle of the electrochemical device, when the pole piece assembly expands along the first direction Z and squeezes the corner of the shell, the first protrusion 105 and / or the second protrusion 106 of the third side wall 107 and / or the fourth side wall 108 can be deformed to provide buffering. At the same time, when the pole piece assembly expands along the third direction Y and pulls the shell, the deformation of the first protrusion 105 and / or the second protrusion 106 of the third side wall 107 and / or the fourth side wall 108 can alleviate the pulling on the corner of the shell, thereby helping to reduce the reverse extrusion force on the corner of the shell and reduce the risk of damage to the corner of the shell.

[0027] In some embodiments of the present application, the third side wall 107 has a first protrusion 105 protruding away from the pole piece assembly. Along the second direction X, the size of the first side wall 101 is L1, and the maximum size of the first protrusion 105 is h1, satisfying: h1≤0.1L1. For example, the value of h1 can be 0.01L1, 0.03L1, 0.05L1, 0.07L1, 0.09L1, 0.1L1, or a range consisting of any two of the above. Figure 1 As shown, the second direction is the X direction, the maximum dimension h1 of the first protrusion is the distance from the top of the first protrusion to the position shown by the dotted line on the same side in the figure in the X direction, and L1 is the dimension of the first side wall in the X direction.

[0028] In some embodiments of the present application, the fourth side wall 108 has a second protrusion 106 protruding away from the pole piece assembly. Along the second direction X, the size of the first side wall 101 is L1, and the maximum size of the second protrusion 106 is h2, satisfying: h2≤0.1L1. For example, the value of h2 can be 0.01L1, 0.03L1, 0.05L1, 0.07L1, 0.09L1, 0.1L1, or a range consisting of any two of the above. Figure 1 As shown, the second direction is the X direction, the maximum dimension h2 of the second protrusion 106 is the distance from the top of the second protrusion 106 to the position shown by the dotted line on the same side in the figure in the X direction, and L1 is the dimension of the first side wall in the X direction.

[0029] By controlling the maximum size of the first protrusion 105 and / or the second protrusion 106 along the second direction X within the above range, the influence of the first protrusion 105 and / or the second protrusion 106 on the volume energy density of the electrochemical device can be reduced.

[0030] In some embodiments of the present application, the third side wall 107 has a first protrusion 105 protruding away from the pole piece assembly, and along the first direction Z, the size of the third side wall 107 is L3; along the second direction X, the maximum size of the first protrusion 105 is h1, satisfying: h1 ≥ 0.002L3. For example, the value of h1 can be 0.002L3, 0.005L3, 0.01L3, 0.015L3, 0.02L3, 0.05L3, 0.08L3, 0.1L3, or a range consisting of any two of the above.

[0031] In some embodiments of the present application, the fourth side wall 108 has a second protrusion 106 protruding away from the pole piece assembly, and along the first direction Z, the size of the fourth side wall 108 is L4; along the second direction X, the maximum size of the second protrusion 106 is h2, satisfying: h2 ≥ 0.002L4. For example, the value of h2 can be 0.002L4, 0.005L4, 0.01L4, 0.015L4, 0.02L4, 0.05L4, 0.08L4, 0.1L4, or a range consisting of any two of the above.

[0032] When the maximum size of the first protrusion 105 and / or the second protrusion 106 along the second direction X is within the above range, when the corner of the shell is squeezed, it can be better deformed to provide buffering, further reducing the risk of damage to the corner of the shell.

[0033] In some embodiments of the present application, along the first direction Z, the size of the first protrusion 105 is w1, satisfying 0.1L3≤w1≤L3. For example, the value of w1 can be 0.1L3, 0.3L3, 0.5L3, 0.7L3, 0.9L3, L3, or a range consisting of any two of the above. Figure 1 As shown, the first direction is the Z direction, the size of the first protrusion in the Z direction is w1, and the size of the third side wall in the Z direction is L3. At this time, w1=L3. Figure 3 and Figure 4 As shown, at this time, w1 <L3。

[0034] In some embodiments of the present application, along the first direction Z, the size of the second protrusion 106 is w2, satisfying 0.1L4≤w2≤L4. For example, the value of w2 can be 0.1L4, 0.3L4, 0.5L4, 0.7L4, 0.9L4, L4, or a range consisting of any two of the above. Figure 1 As shown, the first direction is the Z direction, the size of the second protrusion in the Z direction is w2, and the size of the fourth side wall in the Z direction is L4. At this time, w2=L4. Figure 5 and Figure 6 As shown, at this time, w2 <L3。

[0035] By controlling the size of the first protrusion 105 and / or the second protrusion 106 along the first direction Z within the above range, the first protrusion 105 and / or the second protrusion 106 can meet the expansion requirement of the pole piece assembly through a small amount of deformation, thereby more quickly alleviating the extrusion on the corner of the shell and further reducing the risk of damage to the corner of the shell.

[0036] In some embodiments of the present application, Figure 1 As shown, the raised portion is arc-shaped. Thus, on the one hand, the arc-shaped raised portion is easier to deform and extend, and can deform more quickly when squeezed and pulled to relieve the squeezing of the corner of the shell, thereby further reducing the risk of damage to the corner of the shell. On the other hand, the arc shape is easy to process, and the deformation requirements of the third side wall and / or the fourth side wall are relatively small, so that the structural strength of the third side wall and / or the fourth side wall can be maintained.

[0037] In some embodiments of the present application, the third side wall 107 has a plurality of first protrusions 105 protruding in a direction away from the pole piece assembly. Figure 3 As shown, two first protrusions 105 are provided at the third side wall; Figure 4 As shown, three first protrusions 105 are provided on the third side wall.

[0038] In some embodiments of the present application, the fourth side wall 108 has a plurality of second protrusions 106 protruding in a direction away from the pole piece assembly. Figure 5As shown, two second protrusions 106 are provided at the fourth side wall; Figure 6 As shown, three second protrusions 106 are provided on the fourth side wall.

[0039] The provision of multiple first protrusions 105 and / or multiple second protrusions 106 can increase the deformability of the third side wall 107 and / or the fourth side wall 108, thereby better alleviating the extrusion on the corners of the shell and further reducing the risk of damage to the corners of the shell.

[0040] In some embodiments of the present application, the number of the first protrusions 105 is n1, and 2≤n1≤5. For example, the number of the first protrusions 105 may be 2, 3, 4, or 5.

[0041] In some embodiments of the present application, the number of the second protrusions 106 is n2, and 2≤n2≤5. For example, the number of the second protrusions 106 may be 2, 3, 4, or 5.

[0042] In some embodiments of the present application, the bottom wall 103 includes a first area 111 and a second area 112. When viewed from the third direction, the pole piece assembly covers the first area 111, and the second area 112 exceeds the pole piece assembly and is connected to the protrusion. Figure 1 As shown in FIG. 1 , when both the third side wall 107 and the fourth side wall 108 are provided with protrusions, the first area 111 is the area between the two dotted lines in the figure. Figure 3 and Figure 4 As shown in FIG. 1 , when the third side wall 107 is provided with a protrusion on one side, the first area 111 is the area between the dotted line in the figure and the fourth side wall 108. Figure 5 and Figure 6 As shown, when the fourth side wall 108 is provided with a protrusion on one side, the first area 111 is the area between the dotted line in the figure and the third side wall 107. Figure 1 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the second area 112 is the area between the dotted line and the raised portion on the same side. The bottom wall 103 is connected to the raised portion, and the second area 112 is the portion of the bottom wall 103 close to the raised portion. The second area 112 is beyond the pole piece assembly and connected to the raised portion, and can provide a deformation buffer space. Therefore, when the pole piece assembly expands and pulls the shell along the third direction Y, the second area 112 can reduce the pulling on the corner of the shell by deformation, which is conducive to further reducing the reverse extrusion force on the corner of the shell and reducing the risk of damage to the corner of the shell.

[0043] In some embodiments of the present application, the top wall 104 of the electrochemical device includes a third region 113 and a fourth region 114. When viewed from the third direction, the pole piece assembly covers the third region 113, and the fourth region 114 exceeds the pole piece assembly and is connected to the protrusion. Figure 1 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the third area 113 of the top wall is opposite to the first area 111 of the bottom wall, and the fourth area 114 of the top wall is opposite to the second area 112 of the bottom wall. The top wall 104 is connected to the protrusion, and the fourth area 114 is the part of the top wall close to the protrusion. The fourth area 114 is beyond the pole piece assembly and connected to the protrusion, and can provide a deformation buffer space. Therefore, when the pole piece assembly expands and pulls the shell along the third direction Y, the fourth area 114 can reduce the pulling on the corner of the shell by deformation, which is conducive to further reducing the reverse extrusion force on the corner of the shell and reducing the risk of damage to the corner of the shell.

[0044] In some embodiments of the present application, the top wall 104 and / or the bottom wall 103 of the electrochemical device is in any one of a square, a trapezoid or an L-shape.

[0045] The present application has no particular limitation on the material of the housing, and may include but is not limited to aluminum-plastic film, steel-plastic film, etc.

[0046] The present application has no specific restrictions on the method for preparing the shell, as long as the purpose of the present application can be achieved. For example, the present application can adjust the shape of the mold used for punching the shell (including the number and size of the protrusions) to control the number and size of the protrusions on the side wall of the shell.

[0047] The electrochemical device of the present application is not particularly limited, and may include any device that undergoes an electrochemical reaction. In some embodiments of the present application, the electrochemical device may include, but is not limited to, a lithium ion battery or a sodium ion battery.

[0048] The preparation process of the electrochemical device is well known to those skilled in the art and is not particularly limited in the present application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence, and winding them as needed to obtain an electrode assembly with a wound structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain an electrochemical device; or, stacking the positive electrode sheet, the separator and the negative electrode sheet in sequence, and then fixing the entire stacked structure with tape to obtain an electrode assembly with a stacked structure, placing the electrode assembly in a packaging bag, injecting the electrolyte into the packaging bag and sealing it to obtain an electrochemical device.

[0049] The pole piece assembly of the present application includes a positive pole piece, and the positive pole piece includes a positive current collector and a positive electrode material layer arranged on at least one surface of the positive current collector. The above-mentioned "positive electrode material layer arranged on at least one surface of the positive current collector" means that the positive electrode material layer can be arranged on one surface of the positive current collector along the thickness direction of itself, or it can be arranged on two surfaces of the positive current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive 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. This application has no special restrictions on the positive current collector, as long as the purpose of this application can be achieved. For example, it can include aluminum foil, aluminum alloy foil or a composite current collector (for example, a composite current collector with a metal layer arranged on a polymer layer), etc. The positive electrode material layer includes a positive electrode active material. The present application has no particular restrictions 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 at least one of nickel cobalt manganese oxide, nickel cobalt aluminum oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganese oxide, or lithium iron manganese phosphate. The positive electrode material layer may also include a conductive agent and a binder. The present application has no particular restrictions on the types of conductive agents and binders, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode 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. The present application has no particular restrictions on the thickness of the positive current collector and the positive electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the positive current collector is 5μm to 20μm, and the thickness of the positive electrode material layer is 30μm to 120μm. Optionally, the positive electrode sheet may also include a conductive layer, which is located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited, and 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.

[0050] The pole piece assembly of the present application also includes a diaphragm. The present application has no particular restrictions on the diaphragm, as long as the purpose of the present application can be achieved. For example, in some embodiments of the present application, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric, a film or a composite film with 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 non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. In some embodiments of the present application, the inorganic layer includes inorganic particles and a binder. The present application has no particular restrictions on inorganic particles, such as inorganic particles can include 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 present application has no particular restrictions on binder. In some embodiments of the present application, the polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinyl pyrrolidone, polyvinyl ether or polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene). In the present application, the thickness of the diaphragm is not particularly limited, as long as the purpose of the present application can be achieved, for example, the thickness of the diaphragm can be 3 μm to 30 μm.

[0051] The electrode assembly of the present application also includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer arranged on at least one surface of the negative electrode current collector. The above-mentioned "negative electrode material layer is arranged on at least one surface of the negative electrode current collector" means that the negative electrode material layer can be arranged on one surface of the negative electrode current collector along the thickness direction of itself, or it can be arranged on two surfaces of the negative electrode current collector along the thickness direction of itself. It should be noted that the "surface" here can be the entire area of ​​the surface of the negative electrode current collector, or it can be a partial area of ​​the surface of the negative electrode current collector. This application has no special restrictions, as long as the purpose of this application can be achieved. This application has no special restrictions on the negative electrode current collector, as long as the purpose of this application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper or a composite current collector (for example, a composite current collector with a metal layer arranged on a polymer layer). The negative electrode material layer includes a negative electrode active material. The present application has no particular restrictions 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 at least one of natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composites, or silicon-oxygen composites. In some embodiments of the present application, the negative electrode material layer may also include a conductive agent, a binder, and a thickener. The present application does not particularly limit the types of conductive agents, binders, and thickeners, as long as the purpose of the present application can be achieved. For example, 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, conductive agent, binder, and thickener in the negative electrode 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. The present application does not particularly limit the thickness of the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode material layer is 30 μm to 120 μm. The present application has no particular restrictions 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. Optionally, the negative electrode plate may also include a conductive layer, which is located between the negative electrode current collector and the negative electrode 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.

[0052] The electrochemical device of the present application also includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent. The present application has no particular restrictions on the lithium salt, as long as the purpose of the present application can be achieved. For example, the lithium salt may include but is not limited to at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalate borate) (LiBOB) or lithium difluoroborate. The present application has no particular restrictions on the content of the lithium salt in the electrolyte, as long as the purpose of the present application can be achieved. The present application has no particular restrictions on the non-aqueous solvent, as long as the purpose of the present application can be achieved, for example, the non-aqueous solvent may include but is not limited to at least one of a carbonate compound, a carboxylate compound or an ether compound. The above-mentioned carbonate compound may include but is not limited to at least one of a chain carbonate compound or a cyclic carbonate compound. The above-mentioned 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 ethyl methyl carbonate (MEC). The above-mentioned cyclic carbonate may include but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC) or butylene carbonate (BC). 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, decanolactone, 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 present application has no particular limitation on the content of the non-aqueous solvent in the electrolyte, as long as the purpose of the present application can be achieved.

[0053] A second aspect of the present application provides an electronic device, which includes the electrochemical device in any of the aforementioned embodiments.

[0054] The present application does not particularly limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments of the present application, the electronic device can include but is not limited to a laptop 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.

[0055] Example

[0056] The following examples and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0057] Test methods and equipment:

[0058] The lithium-ion batteries of the embodiments and comparative examples were subjected to a cycle test. Twenty lithium-ion batteries were taken from each group and charged to 4.35V at a constant current of 1C at 25°C±5°C, then charged to a cut-off current of 0.05C at a constant voltage at 4.35V, and then discharged to 2.5V at a constant current of 1C. This was one charge and discharge cycle. The above charge and discharge cycles were repeated 600 times, and the number of batteries with damaged shell corners and leakage was counted.

[0059] Example 1-1

[0060] <Preparation of positive electrode sheet>

[0061] The positive electrode active material lithium cobalt oxide, the conductive agent Super P, and the binder polyvinylidene fluoride were mixed in a mass ratio of 97.9:0.9:1.2, and N-methylpyrrolidone (NMP) was added to prepare a slurry with a solid content of 75wt%. The positive electrode slurry was obtained after being stirred evenly by a vacuum mixer. The positive electrode slurry was 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 positive electrode material layer. The coating weight of the positive electrode material layer was 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 material layer on both sides. After drying at 120°C, cold pressing, cutting and welding the tabs, a positive electrode sheet with a specification of 74mm×867mm is obtained for standby use.

[0062] <Preparation of negative electrode sheet>

[0063] The negative electrode active material (artificial graphite: silicon carbon material mass ratio of 9:1), binder styrene butadiene rubber, and thickener sodium carboxymethyl cellulose were mixed in a mass ratio of 97.4:1.4:1.2, and deionized water was added to prepare a slurry with a solid content of 45wt%. The negative electrode slurry was obtained after stirring evenly with 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 single-sided coating of a negative electrode material layer. The coating weight of the negative electrode 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 material layer on both sides. After drying at 120°C, cold pressing, cutting and welding the tabs, a negative electrode sheet with a specification of 78mm×875mm is obtained for standby use.

[0064] <Preparation of Electrolyte>

[0065] In an environment where the water content is less than 10 ppm, dimethyl carbonate, diethyl carbonate and ethylene carbonate are mixed in a mass ratio of 1:1:1 to obtain an organic solvent, and then electrolyte salt LiPF6 is added to the organic solvent and mixed evenly to obtain an electrolyte solution. Among them, based on the mass of the electrolyte solution, the mass percentage of LiPF6 is 12.5%, and the rest is the organic solvent.

[0066] <Diaphragm>

[0067] A 5 μm thick polyethylene porous film was used as the substrate layer of the separator. A 2 μm thick alumina ceramic layer was coated on one surface of the substrate layer, and then 2.5 mg / 1540.25 mm 2 The bonding layer is dried to obtain a diaphragm. The alumina ceramic layer contains 84% ​​aluminum oxide and 16% polyvinylidene fluoride by mass; the bonding layer is made of polyvinylidene fluoride.

[0068] <Preparation of packaging bags>

[0069] The aluminum-plastic film is punched with a mold having a protrusion on the side. Along the first direction, the length L (L3 and L4) of the punching hole is 50 mm; along the second direction, the width W (L1 and L2) of the punching hole is 35 mm; at the same time, the third side wall and the fourth side wall of the packaging bag have an arc-shaped protrusion with a maximum dimension h of 0.001L along the second direction and a dimension w of L along the first direction.

[0070] <Preparation of lithium-ion batteries>

[0071] The positive electrode sheet, separator and negative electrode sheet prepared above are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the electrode assembly is wound. The electrode assembly is put into a packaging bag, and the pole ear extends out of the packaging bag from the first side wall side, and the moisture is removed at 80°C, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, degassing, trimming and other processes, a lithium-ion battery is obtained. Among them, the main part of the lithium-ion battery is 50mm long, 35mm wide and 4.8mm thick.

[0072] Example 1-2

[0073] Except for adjusting the height of the protrusion on the side of the mold so that the size h of the protrusions on both sides of the packaging bag is 0.002L, the rest is the same as Example 1-1.

[0074] Examples 1-3

[0075] Except for adjusting the height of the protrusion on the side of the mold so that the size h of the protrusions on both sides of the packaging bag is 0.003L, the rest is the same as Example 1-1.

[0076] Examples 1-4

[0077] Except for adjusting the height of the protrusion on the side of the mold so that the size h of the protrusions on both sides of the packaging bag is 0.005L, the rest is the same as Example 1-1.

[0078] Examples 1-5

[0079] Except for adjusting the height of the protrusion on the side of the mold so that the size h of the protrusions on both sides of the packaging bag is 0.01L, the rest is the same as Example 1-1.

[0080] Example 2-1

[0081] Except for adjusting the number and width of the protrusions on the side of the mold so that the number of protrusions on both sides of the packaging bag is 2 and w is 0.5L, the rest is the same as Example 1-2.

[0082] Example 2-2

[0083] Except for adjusting the number and width of the protrusions on the side of the mold so that the number of protrusions on both sides of the packaging bag is 3 and w is 0.33L, the rest is the same as Example 1-2.

[0084] Example 2-3

[0085] Except for adjusting the number and width of the protrusions on the side of the mold so that the number of protrusions on both sides of the packaging bag is 4 and w is 0.25L, the rest is the same as Example 1-2.

[0086] Embodiment 2-4

[0087] Except for adjusting the number and width of the protrusions on the side of the mold so that the number of protrusions on both sides of the packaging bag is 5 and w is 0.2L, the rest is the same as Example 1-2.

[0088] Comparative Example 1

[0089] Except for adjusting the side of the mold to have no protrusion so that the packaging bag has no protrusion, the rest is the same as Example 1-1.

[0090] The dimensional parameters of the protrusion and the experimental results are shown in the following table.

[0091]

[0092] From the comparison of Examples 1-1 to 1-5 with Comparative Example 1, it can be seen that the provision of a protrusion on the third side wall and / or the fourth side wall of the packaging bag can reduce the number of batteries with damaged shell corners and leakage during the cycle. And when the size of the protrusion is controlled to meet h≥0.002L, the number of batteries with damaged shell corners and leakage is further reduced, while in Comparative Example 1, since no protrusion is provided, the number of batteries with damaged shell corners and leakage is relatively large. From the comparison of Examples 1-2 with Examples 2-1 to 2-4, it can be seen that by providing multiple protrusions, the number of batteries with damaged shell corners and leakage during the cycle can be further reduced.

[0093] 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. An electrochemical device, comprising a shell and an electrode assembly; the electrode assembly comprises a pole piece assembly housed in the shell and a pole ear connected to the pole piece assembly, the pole ear extending out of the shell along a first direction; along the first direction, the shell comprises a first side wall and a second side wall arranged opposite to each other, the shell further comprises a third side wall and a fourth side wall arranged opposite to each other along the second direction, and a top wall and a bottom wall arranged opposite to each other along the third direction; the first direction, the second direction and the third direction are perpendicular to each other; at least one of the third side wall and the fourth side wall has a protrusion protruding away from the pole piece assembly.

2. The electrochemical device according to claim 1, wherein: The electrochemical device satisfies at least one of the following conditions: (1) The third side wall has a first protrusion protruding in a direction away from the pole piece assembly. Along the second direction, the size of the first side wall is L1, and the maximum size of the first protrusion is h1, satisfying: h1≤0.1L1; (2) The fourth side wall has a second protrusion protruding in a direction away from the pole piece assembly. Along the second direction, the size of the first side wall is L1, and the maximum size of the second protrusion is h2, satisfying: h2≤0.1L1.

3. The electrochemical device according to claim 1, wherein The electrochemical device satisfies at least one of the following conditions: (1) The third side wall has a first protrusion protruding in a direction away from the pole piece assembly, and along the first direction, the dimension of the third side wall is L3; along the second direction, the maximum dimension of the first protrusion is h1, and the following is satisfied: h1 ≥ 0.002L3; (2) The fourth side wall has a second protrusion protruding away from the pole piece assembly. Along the first direction, the size of the fourth side wall is L4; along the second direction, the maximum size of the second protrusion is h2, satisfying: h2≥0.002L4.

4. The electrochemical device according to claim 3, wherein: The electrochemical device satisfies at least one of the following conditions: (1) Along the first direction, the size of the first protrusion is w1, 0.1L3≤w1≤L3; (2) Along the first direction, the size of the second protrusion is w2, 0.1L4≤w2≤L4.

5. The electrochemical device according to any one of claims 1 to 4, wherein: The raised portion is arc-shaped.

6. The electrochemical device according to claim 1, wherein The electrochemical device satisfies at least one of the following conditions: (1) The third side wall has a plurality of first protrusions protruding in a direction away from the pole piece assembly; (2) The fourth side wall has a plurality of second protrusions protruding in a direction away from the pole piece assembly.

7. The electrochemical device according to claim 6, wherein: The electrochemical device satisfies at least one of the following conditions: (1) The number of the first protrusions is n1, 2≤n1≤5; (2) The number of the second protrusions is n2, and 2≤n2≤5.

8. The electrochemical device according to claim 1, wherein The electrochemical device satisfies at least one of the following conditions: (1) The bottom wall includes a first area and a second area. When viewed along the third direction, the pole piece assembly covers the first area, and the second area exceeds the pole piece assembly and is connected to the protrusion; (2) The top wall includes a third area and a fourth area. When viewed along the third direction, the pole piece assembly covers the third area, and the fourth area extends beyond the pole piece assembly and is connected to the protrusion.

9. The electrochemical device according to claim 1, wherein: The top wall and / or bottom wall may be in any of a square, trapezoidal or L-shaped shape.

10. An electronic device, comprising the electrochemical device according to any one of claims 1 to 9.

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