Electrode assembly and battery

Abstract

Provided are an electrode assembly and a battery. Electrode sheets (100) and separators of the electrode assembly are wound multiple times to form a flat electrode body (10), wherein at least one electrode sheet (100) is provided with bumps (200), a straight part (11) of the electrode body (10) has a first thickness L1 in a first direction, and a corner part (12) of the electrode body (10) has a second thickness L2 in a second direction, L1 and L2 satisfying: 1.5≤L1 / L2≤2.4. When an electrode sheet (100) is provided with bumps (200), the interlayer interaction force of the electrode body (10) is appropriate, and the bumps (200) are not prone to deformation under the action of a winding stress and an expansion force, such that the bumps (200) can stably support the separators (13). When the electrode assembly is applied to the battery, the performance of the battery can also be optimized.

Description

Electrode assembly and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on January 26, 2024, with application number 202410111652.6 and invention name “An Electrode Assembly and Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of chemical devices, and in particular to an electrode assembly and a battery. Background Art

[0004] Cycle life is a key performance of lithium-ion batteries. Improving cycle life is a long-term and continuous research and development direction. In addition to improving the battery material end through optimization and innovation, its cycle life can also be effectively promoted through structural design and improvement. This also places more design requirements on the winding structure of the electrode assembly of the battery cell. Summary of the Invention

[0005] The inventors discovered that winding stress can cause interlayer compression in electrode assemblies, including between corners and straight sections. During battery charge and discharge, the electrode assembly expands, exacerbating this compression. This can lead to insufficient electrolyte between the layers, poor wetting, and potentially deteriorating interfaces, leading to poor wetting and cycle failure.

[0006] The embodiments of the present application provide a pole piece, an electrode assembly, and a battery, which can improve the extrusion problem between layers of the electrode assembly.

[0007] In a first aspect, an embodiment of the present application provides an electrode assembly for a battery, the electrode assembly comprising a plurality of electrode sheets and a separator disposed between two of the electrode sheets, wherein at least one of the electrode sheets comprises a plurality of protrusions;

[0008] In some exemplary embodiments, the pole piece includes a main body, wherein a plurality of protrusions are protruding from the main body.

[0009] The electrode sheet and the isolation membrane are wound multiple times to form a flat electrode body, and the electrode body includes a straight portion and two corner portions. The straight portion has a first thickness L1 in a first direction, and the two corner portions are arranged at opposite ends of the straight portion in a second direction perpendicular to the first direction. The corner portions have a second thickness L2 in the second direction, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.4.

[0010] In some exemplary embodiments, each circle of the pole piece includes two straight sections arranged opposite to each other along the first direction, and two corner sections arranged at both ends of the straight section along the second direction;

[0011] The pole piece has a tail end provided corresponding to the straight section of the outermost pole piece, and all the straight sections and the tail end stacked in the first direction form the straight portion; the first thickness L1 is the thickness of the straight portion passing the tail end in the first direction;

[0012] All the corner segments located on the same side of the straight segment in the second direction form a corner portion, and the second thickness L2 is the thickness of the corner portion at the midpoint of a line connecting two ends of an innermost corner segment in the second direction.

[0013] In some exemplary embodiments, the number of winding turns of the pole piece of the electrode body is an even number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.2; or, the number of winding turns of the pole piece of the electrode body is an odd number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.4.

[0014] In some exemplary embodiments, the protrusion includes a first protrusion formed on the straight portion and a second protrusion formed on the corner portion, the height of the first protrusion is H1, and the height of the second protrusion is H2, wherein H1 and H2 satisfy: 1.5≤H2 / H1≤5.

[0015] In some exemplary embodiments, H1 satisfies: 5 μm≤H1≤40 μm; and / or H2 satisfies: 20 μm≤H2≤80 μm.

[0016] In some exemplary embodiments, the inner surface of the convex portion has a preset spherical diameter SD1, where the preset spherical diameter SD1 is the spherical diameter of the inscribed sphere on which the inner surface of the convex portion is located, and SD1 satisfies: 2mm≤SD1≤30mm.

[0017] In some exemplary embodiments, the pole piece includes a current collector and an active material layer disposed on the surface of the current collector, the surface of the active material layer facing away from the current collector has a convex area, the convex portion is located in the convex area, and the convex area is spaced apart from the edge of the active material layer.

[0018] In some exemplary embodiments, the electrode assembly further includes a tab assembly, wherein the tab assembly partially covers the convex area; the convex portion includes a main convex portion and an auxiliary convex portion, the main convex portion is formed by bending a portion of the current collector and a portion of the active material layer toward the same side, and the auxiliary convex portion is formed by bending a portion of the current collector, a portion of the active material layer and a portion of the tab assembly toward the same side.

[0019] In some exemplary embodiments, the portion of the current collector used to form the main protrusion is a first substrate, the inner surface of the first substrate has a first inner peripheral edge line, the first inner peripheral edge line has a main circumscribed circle, and the diameter of the main circumscribed circle is r1; the portion of the current collector used to form the auxiliary protrusion is a second substrate, the inner surface of the second substrate has a second inner peripheral edge line, the second inner peripheral edge line has an auxiliary circumscribed circle, and the diameter of the auxiliary circumscribed circle is r2; and the electrode assembly satisfies at least one of the following conditions:

[0020] Ⅰ, r1≤r2;

[0021] Ⅱ, 0.3mm≤r1≤10mm;

[0022] Ⅲ, 0.3mm≤r2≤10mm.

[0023] In some exemplary embodiments, the inner surface of the main protrusion has a first preset spherical diameter SD11, which is the spherical diameter of a first circumscribed sphere on which the inner surface of the main protrusion is located; the inner surface of the auxiliary protrusion has a second preset spherical diameter SD12, which is the spherical diameter of a second circumscribed sphere on which the inner surface of the auxiliary protrusion is located; and the electrode assembly satisfies at least one of the following conditions:

[0024] (1) SD11≤SD12;

[0025] (2) 2mm≤SD11≤10mm;

[0026] (3)10mm≤SD12≤30mm.

[0027] In some exemplary embodiments, the tab assembly is spaced apart from the main protrusion, the outer surface of the main protrusion has a protrusion edge line, and the minimum spacing between the tab assembly and the protrusion edge line is T2, and T2 satisfies: 0.5mm≤T2≤30mm.

[0028] In some exemplary embodiments, the tab assembly includes a metal tab and an insulating protective adhesive; the insulating protective adhesive satisfies at least one of the following conditions:

[0029] a. The puncture resistance of the insulating protective adhesive is P, and P satisfies: 7N≤P≤12N;

[0030] b. The elongation of the insulating protective adhesive is Q, and Q satisfies: 60%≤Q≤120%;

[0031] c. The thickness of the insulating protective adhesive is W, and W satisfies: 16 μm ≤ W ≤ 100 μm.

[0032] In some exemplary embodiments, the surface of the active material layer facing away from the current collector further has a tab mounting area, the tab mounting area is connected to the convex area and is spaced apart from the edge of the active material layer, and the tab assembly is arranged in the tab mounting area to avoid the convex portion.

[0033] In some exemplary embodiments, the protrusion provided on the straight portion protrudes toward one side of the winding center of the electrode body; the protrusion provided on the corner portion protrudes toward a side away from the winding center of the electrode body; or, the protrusion provided on the corner portion protrudes toward one side of the winding center of the electrode body.

[0034] In a second aspect, an embodiment of the present application provides a battery, comprising a housing and the electrode assembly as described above, wherein the electrode assembly is disposed in an internal space of the housing.

[0035] Based on the electrode assembly and battery of the embodiments of the present application, by setting L1 and L2 to satisfy 1.5≤L1 / L2≤2.4, it is easy to control the winding conditions of the electrode body, so that the interlayer interaction force of the electrode body formed after winding is appropriate. When the electrode assembly is applied to the battery and during the battery's use, the electrode assembly can buffer the extrusion caused by the electrode assembly's own expansion force, and the electrode assembly still has a good electrolyte infiltration effect. Furthermore, in the case of a pole piece with a protrusion, the interlayer interaction force of the electrode body is appropriate, and the protrusion will not easily deform under the action of winding stress and expansion force, so that the protrusion can provide stable support for the separator. When the electrode assembly is applied to the battery, the battery performance can also be optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0037] FIG1 is a schematic cross-sectional view of an electrode body according to an embodiment of the present application;

[0038] FIG2 is a schematic diagram of the front view of the pole piece in an expanded state according to an embodiment of the present application;

[0039] FIG3 a is a schematic diagram of a partial cross-sectional structure of a first convex portion and a second convex portion of a pole piece in an expanded state according to an embodiment of the present application;

[0040] FIG3 b is a schematic diagram of a partial cross-sectional structure of the first and second convex portions of a pole piece in a wound state according to an embodiment of the present application;

[0041] FIG4 is a schematic diagram of the expanded structure of a pole piece having a pole tab mounting area according to an embodiment of the present application;

[0042] FIG5 is a schematic diagram of an expanded structure of a pole piece having a first convex region and a second convex region according to an embodiment of the present application;

[0043] FIG6 is a schematic cross-sectional view of the main protrusion and the auxiliary protrusion of a pole piece in an expanded state according to an embodiment of the present application.

[0044] Figure numerals: 10, electrode body; 11, straight portion; 12, corner portion; 13, separator; 100, pole piece; 101, straight section; 102, corner section; 103, tail end; 110, current collector; 120, active material layer; 121, bump area; 1211, first bump area; 1212, second bump area; 1213, first edge; 1214, second edge; 1215, first boundary; 1216, second boundary; 122, first region; 123, second region; 124, head avoidance area; 125, tail avoidance area; 126, tab mounting area; 200, convex portion; 221, inner surface; 2201, inscribed edge line; 222, outer surface; 2202, convex portion edge line; 201, First protrusion; 202, second protrusion; 210, main protrusion; 211, first base; 2111, first inner peripheral edge line; 220, auxiliary protrusion; 212, second base; 2121, second inner peripheral edge line; 300, main body; 400, tab assembly; 410, tab; 420, insulating protective glue; M, first direction; N, second direction. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0046] The inventors discovered that the winding stress generated by the winding of the battery's electrode assembly will cause extrusion on various parts of the electrode sheet. During the battery's charging and discharging process, the electrode assembly expands, and the extrusion of the corner part of the electrode assembly will be further aggravated, resulting in insufficient electrolyte in the corner part, poor infiltration, and easy interface deterioration, and even cycle failure.

[0047] The inventors also discovered that in the process of processing the electrode assembly, the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound multiple times in sequence to form an electrode body with multiple winding units. By increasing the spacing between two adjacent winding units and providing a protrusion on the electrode sheet to support the two adjacent winding units, the interface problem of the electrode sheet in the corner part can be improved. However, since the protrusion is easily affected by the expansion force generated by the expansion of the electrode assembly and the winding stress generated by the winding, excessive expansion force or winding stress can easily cause the protrusion to collapse, deform, and other uncontrollable situations, resulting in insufficient support for the protrusion, and can also easily cause damage to the active material layer of the electrode sheet, affecting the normal use of the battery. Based on the above content, the embodiment of the present application provides an electrode assembly and a battery, and designs the winding structure of the electrode assembly so that the protrusion can stably and effectively play its supporting role.

[0048] As shown in Figure 1, the electrode assembly of an embodiment of the present application includes two electrode sheets 100 of opposite polarity and a separator 13 disposed between the two electrode sheets 100. As shown in Figure 2, a schematic diagram of the front view of one of the electrode sheets 100 in an unfolded state is shown. The electrode sheets 100 have a length direction X, a width direction Y, and a thickness direction Z that are perpendicular to each other. The length direction X, width direction Y, and thickness direction Z of the two electrode sheets 100 of opposite polarity are consistent. The separator 13 is disposed between the two electrode sheets 100 of opposite polarity in the thickness direction Z. One of the two electrode sheets 100 of opposite polarity is a positive electrode sheet and the other is a negative electrode sheet. The separator 13 has insulating properties and is used to separate the positive electrode sheet from the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from shorting.

[0049] In the embodiment of the present application, the isolation film 13 and the two electrode sheets 100 are wound multiple times along the length direction X of the electrode sheet 100 to form the electrode body 10. The length direction X of the electrode sheet 100 is the direction in which the electrode sheet 100 is wound. As shown in FIG1 , the electrode body 10 is flat and has a first direction M and a second direction N. Each turn of the electrode sheet 100 includes two straight sections 101 arranged opposite to each other along the first direction M of the electrode body 10, and two corner sections 102 arranged at both ends of the straight section 101 along the second direction N of the electrode body 10. The first direction M is perpendicular to the second direction N. The first direction M is a direction perpendicular to the plate surface of the straight section 101 of the electrode sheet 100, and the second direction N is a direction parallel to the plate surface of the straight section 101 of the electrode sheet 100.

[0050] In some embodiments of the present application, at least one of the two pole pieces 100 includes a main body 300 and a plurality of protrusions 200 protruding from the main body 300. After the two pole pieces 100 and the isolation membrane 13 are wound multiple times to form the electrode body 10, the protrusions 200 contact the isolation membrane 13 to provide support, and there is a gap between the isolation membrane 13 and the main body 300, so that there is space between the isolation membrane 13 and the main body 300 to accommodate the electrolyte, thereby improving the electrolyte infiltration effect.

[0051] The straight section 101 and the corner section 102 both have convex portions 200 so that the isolation membrane 13 corresponding to the straight section 101 and the corner section 102 can be supported. Optionally, all convex portions 200 provided on a single pole piece 100 protrude toward the same side of the pole piece 100 in the thickness direction Z of the pole piece 100. For example, the convex portion 200 provided on the straight section 101 protrudes toward the side of the winding center of the electrode body 10, and the convex portion 200 provided on the corner section 102 protrudes toward the side where the winding center of the electrode body 10 is located; or, the convex portion 200 provided on the straight section 101 protrudes toward the side away from the winding center of the electrode body 10, and the convex portion 200 provided on the corner section 102 protrudes toward the side away from the winding center of the electrode body 10. Optionally, a portion of the protrusions 200 provided on a single pole piece 100 protrudes toward one side of the pole piece 100 in the thickness direction Z of the pole piece 100, and another portion of the protrusions 200 protrudes toward the other side of the pole piece 100 in the thickness direction Z of the pole piece 100. For example, the protrusions 200 provided on the straight section 101 protrude toward one side of the winding center of the electrode body 10, and the protrusions 200 provided on the corner section 102 protrude toward the side away from the winding center of the electrode body 10; or, the protrusions 200 provided on the straight section 101 protrude toward the side away from the winding center of the electrode body 10, and the protrusions 200 provided on the corner section 102 protrude toward the side of the winding center of the electrode body 10.

[0052] Optionally, the protrusions 200 of the multiple pole pieces 100 of the electrode body 10 protrude toward the same side, for example, the protrusions 200 of the multiple pole pieces 100 all protrude toward one side of the winding center of the electrode body 10; or, the protrusions 200 of the multiple pole pieces 100 all protrude toward a side away from the winding center of the electrode body 10. Optionally, the protrusions 200 of all straight sections 101 of the multiple pole pieces 100 of the electrode body 10 protrude toward one side of the winding center of the electrode body 10, and the protrusions 200 of all bent sections of the multiple pole pieces 100 protrude toward a side away from the winding center of the electrode body 10.

[0053] Preferably, the protrusion 200 provided on the straight section 101 protrudes toward one side of the winding center of the electrode body 10, so that the outer peripheral wall surface of the outermost circle electrode piece 100 is smooth, and the protrusion 200 on the inner circle electrode piece 100 can better provide support for the inner circle electrode piece 100, so as to improve the electrolyte infiltration effect of the inner circle electrode piece 100.

[0054] In the winding direction of the electrode 100, the electrode 100 has a winding head and a tail end 103 that are arranged opposite to each other. The electrode 100 is wound multiple times starting from the winding head and is tailed at the tail end 103. The wound electrode 100 has a multi-turn winding unit. In the embodiment of the present application, a turn structure formed by connecting two straight sections 101 and two corner sections 102 end to end is a complete winding unit. The winding head and the tail end 103 exist in an incomplete turn layer. The winding head is arranged corresponding to the straight section 101 of the innermost winding unit, and the tail end 103 is arranged corresponding to the straight section 101 of the outermost winding unit. The electrode assembly also includes a tail end adhesive, which is bonded to the tail end 103 and the straight section 101 of the outermost winding unit to fix the position of the tail end 103.

[0055] The electrode body 10 includes a straight portion 11 and two corner portions 12. Specifically, the straight segments 101 of each coil electrode 100 are stacked in the first direction M, and all the straight segments 101 and the tail end 103 stacked in the first direction M form the straight portion 11, and the straight portion 11 has a first thickness L1 in the first direction M; all the corner segments 102 located on the same side of the straight segment 101 in the second direction N form the corner portion 12, that is, the electrode body 10 has two corner portions 12, one of which is connected to one end of the straight portion 11 in the second direction N, and the other corner portion 12 is connected to the other end of the straight portion 11, and each corner portion 12 has a second thickness L2 in the second direction N. The second thickness L2 of one corner portion 12 is denoted as L21, and the second thickness L2 of the other corner portion 12 is denoted as L22. Due to the influence of the winding process, the second thickness L2 of the two corner portions 12 is equal or approximately equal. The difference in the second thickness L2 of the two corner portions 12 is ΔL2, where ΔL2 = |L22 - L21|, 0 ≤ ΔL2 ≤ 5% * (L21 + L22) / 2. Furthermore, as shown in FIG1 , the first thickness L1 is the thickness of the straight portion 11 passing through the tail end 103 in the first direction M, and the second thickness L2 is the thickness of the corner portion 12 passing through the midpoint of the line connecting the two ends of the innermost corner segment 102 in the second direction N.

[0056] Among them, L1 and L2 satisfy: 1.5≤L1 / L2≤2.4. For example, L1 / L2 can be 1.5, 1.8, 1.9, 2.0, 2.2, 2.3, 2.4, or a range consisting of any two thereof. By setting L1 and L2 to satisfy 1.5≤L1 / L2≤2.4, it is easy to control the winding conditions of the electrode body 10, so that the interlayer interaction force of the electrode body 10 formed after winding is appropriate. When the electrode assembly is applied to the battery and during the use of the battery, the electrode assembly can buffer the extrusion caused by the expansion force of the electrode assembly itself, and the electrode assembly still has a good electrolyte infiltration effect. In addition, when the electrode sheet 100 has a protrusion 200, the interlayer interaction force of the electrode body 10 is appropriate, and the protrusion 200 will not easily deform under the action of winding stress and expansion force, so that the protrusion 200 can provide stable support for the separator 13. When the electrode assembly is applied to the battery, the performance of the battery can also be optimized.

[0057] It is understood that due to the different sizes of the electrode sheets 100, the number of winding units formed by the electrode sheets 100 of different electrode assemblies after winding varies, and the number can be an even or odd number. In addition, the positive electrode sheet or the negative electrode sheet can be placed on the outer ring for the end termination. For example, in the embodiment of the present application, the positive electrode sheet is placed on the outer ring for the end termination, and the end termination end 103 is the end termination end 103 of the positive electrode sheet. The number of winding layers of the electrode sheet is counted based on the number of winding units of the positive electrode sheet.

[0058] Among them, when the electrode sheet 100 (including the positive electrode sheet and the negative electrode sheet) of the electrode assembly does not have the protrusion 200, the electrode body 10 has a first thickness L1' passing the tail end 103 of the electrode sheet 100 and in the first direction M, and the corner portion 12 has a second thickness L2' passing the midpoint of the line connecting the two ends of the innermost corner segment 102 and in the second direction N. If the winding stress inside the electrode body 10 is not considered, L1' and L2' satisfy: L1'=2L2'. However, the electrode body 10 is actually affected by the internal winding stress and expansion force. Different electrode bodies 10 are affected by different winding stress and expansion force. The value of L1' fluctuates around 2L2'. In addition, L1' and L2' are also affected by the number of winding layers. When the number of winding layers is an even number, 2L2'≤L1'≤2.2L2', and when the number of winding layers is an odd number, 2L2'≤L1'≤2.5L2'. When these conditions are met, under the influence of winding stress and expansion force, the electrode assembly can maintain a good gap between the electrode piece 100 and the isolation membrane 13, so that the electrode assembly can have a good electrolyte infiltration effect.

[0059] When the electrode sheet 100 (including the positive electrode sheet and the negative electrode sheet) of the electrode assembly has a protrusion 200, the value of L2 increases relative to the value of L2' relative to the case where the protrusion 200 is not provided, that is, the second thickness L2 is set thicker. It can be understood that due to the expansion force and winding stress, the corner portions 12 of the two adjacent circles of electrode sheets 100 are prone to mutual compression, and the straight portion 11 and the corner portion 12 of each circle of electrode sheets 100 are also squeezed. The greater the degree of compression, the more likely it is that there will be problems such as insufficient electrolyte and poor infiltration, which will lead to deterioration of the interface of the electrode sheet 100 and even cycle failure. Therefore, the value of the second thickness L2 is set to be larger so that the corner portion 12 can better buffer the expansion stress and winding stress.

[0060] Specifically, when the number of turns of the electrode piece 100 of the electrode body 10 is an even number, L1 and L2 satisfy: 1.5≤L1 / L2≤2.2, for example, L1 / L2 can be 1.5, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, or a range consisting of any two thereof. When the number of turns of the electrode piece 100 of the electrode body 10 is an odd number, L1 and L2 satisfy: 1.5≤L1 / L2≤2.4, for example, L1 / L2 can be 1.5, 1.6, 1.7, 2.0, 2.2, 2.3, 2.4, or a range consisting of any two thereof.

[0061] The greater second thickness L2 of the corner portion 12 is primarily due to the fact that the height of the protrusion 200 of the corner section 102 is greater than that of the protrusion 200 of the straight section 101. The protrusion 200 has an outer surface 222, which includes a protrusion vertex Q and a protrusion edge line 2202. The protrusion edge line 2202 is connected to the surface of the main body 300. The height of the protrusion 200 is the distance from the protrusion vertex Q to the plane in which the protrusion edge line 2202 lies, in a direction perpendicular to the plane in which the protrusion edge line 2202 lies. 3a and 3b , the protrusion 200 includes a first protrusion 201 formed on the straight section 101 and a second protrusion 202 formed on the corner section 102. The height of the first protrusion 201 is H1, and the height of the second protrusion 202 is H2. H1 and H2 satisfy the following relationship: 1.5≤H2 / H1≤5. For example, H2 / H1 can be 1.5, 1.8, 2.0, 2.5, 3, 4, 5, or any two thereof. Thus, the height H2 of the second protrusion 202 is set to be greater than the height H1 of the first protrusion 201. The second protrusion 202 provides support for the separator 13, increasing the gap between the main body 300 of the corner section 102 and the separator 13. This allows for better response to expansion and extrusion, maintaining good electrolyte wetting in the corner portion 12.

[0062] Optionally, H1 satisfies the following: 5μm≤H1≤40μm. For example, H1 can be 5μm, 10μm, 20μm, 25μm, 30μm, 40μm, or a range consisting of any two thereof. H2 satisfies the following: 20μm≤H2≤80μm. For example, H2 can be 20μm, 30μm, 40μm, 50μm, 60μm, 80μm, or a range consisting of any two thereof. Within the above range, it is convenient to set the main portion 300 of the corner section 102 and the main portion 300 of the straight section 101 to have an appropriate distance from the corresponding isolation membrane 13, thereby improving the infiltration of the electrolyte solution. At the same time, the height of the first protrusion 201 and the second protrusion 202 is not too large, preventing the first protrusion 201 and the second protrusion 202 from excessively occupying space, thereby reducing the energy density of the battery when used in the battery.

[0063] The outer surface 222 of the convex portion 200 includes an outer top surface, an outer main surface, and an outer transition surface, which are connected in sequence. The outer top surface is used to contact the isolation membrane 13 and is a spherical surface located on the sphere U1. The convex portion vertex Q is formed on the outer top surface. The outer transition surface is an arc surface, and the curvature of the outer transition surface is opposite to the curvature of the outer top surface. The edge of the outer transition surface away from the outer top surface forms a convex portion edge line 2202. The outer main surface is connected between the outer top surface and the outer transition surface. The outer main surface can also be an arc surface, or, in the height direction of the convex portion 200, the cross-sectional profile of the outer main surface forms a circle or a polygon. Regarding the shape of the outer main surface, this application does not limit it, and it can be selected according to actual needs.

[0064] The inner surface 221 of the protrusion 200 includes an inner top surface, an inner main surface, and an inner transition surface connected in sequence. The inner top surface is a spherical surface located on the sphere U2, and the inner top surface and the outer top surface are provided with a sphere center. The shape of the inner surface 221 of the protrusion 200 can be similar to the shape of the outer surface 222 of the protrusion 200. The shape of the inner surface 221 of the protrusion 200 is not further described here. Among them, the edge of the inner transition surface away from the inner top surface forms an inscribed edge line 2201, and the inscribed edge line 2201 is connected to the surface of the main body 300. As shown in Figure 3a, the inner surface 221 of the protrusion 200 also has a first inner diameter R. The first inner diameter R is the diameter of the first circumscribed circle of the inscribed edge line 2201. R satisfies the following: 0.3mm≤R≤10mm. For example, R can be 0.3mm, 1mm, 2mm, 5mm, 6mm, 8mm, 10mm, or a range consisting of any two thereof. Within the above range, it is convenient to control the area occupied by the protrusion 200 within an appropriate range, prevent the area occupied by the protrusion 200 from being too small or too large, and prevent it from being difficult to take into account the electrolyte infiltration and support strength requirements. In combination with the height of the protrusion 200, it is also convenient to prevent the area occupied by the protrusion 200 from being too small, resulting in the protrusion 200 being sharp and easily causing damage to the isolation membrane 13, and prevent the area occupied by the protrusion 200 from being too large, resulting in insufficient space between the isolation membrane 13 and the main body 300.

[0065] As shown in FIG2 , the inner surface 221 of the protrusion 200 has a predetermined spherical diameter SD1. The predetermined spherical diameter SD1 is the diameter of the inscribed sphere within which the inner surface of the protrusion 200 is located. Specifically, the predetermined spherical diameter SD1 is the diameter of the sphere U2 within which the inner top surface is located. SD1 satisfies the following: 2 mm ≤ SD1 ≤ 30 mm. For example, SD1 can be 2 mm, 6 mm, 8 mm, 10 mm, 15 mm, 20 mm, 30 mm, or any two thereof. Within this range, the degree of curvature of the protrusion 200 relative to the main body 300 can be controlled within an appropriate range, preventing the protrusion 200 from easily breaking relative to the main body 300. Furthermore, in combination with the first inner diameter R and the height of the protrusion 200, the protrusion 200 is appropriately sized to meet support requirements while ensuring an appropriate space between the isolation membrane 13 and the main body 300. Furthermore, the protrusion 200 has good structural stability and is not easily deformed by expansion forces and winding stresses.

[0066] The pole piece 100 includes a current collector 110 and an active material layer 120 provided on the surface of the current collector 110. Specifically, the current collector 110 has two surfaces arranged opposite to each other in the thickness direction Z of the pole piece 100. Optionally, the active material layer 120 is provided on one of the surfaces of the current collector 110, or the active material layer 120 is provided on two opposite surfaces of the current collector 110. The active material layer 120 of the pole piece 100 is provided on the surface of the current collector 110, and in the thickness direction Z of the pole piece 100, the active material layer 120 covers the entire surface of the current collector 110. In some other embodiments, the current collector 110 includes a coating portion and a hollow foil portion, the hollow foil portion is connected to the outside of the coating portion in the width direction Y of the pole piece 100, and the active material layer 120 covers the entire surface of the coating portion and avoids the surface of the hollow foil portion. This design can better reduce lithium plating, reduce the impact of cold pressing on cell deformation, and improve the safety performance of the battery.

[0067] The surface of the active material layer 120 facing away from the current collector 110 has a convex area 121. As shown in Figure 2, the protrusion 200 is located in the convex area 121, and the convex area 121 is spaced apart from the edge of the active material layer 120. Specifically, the surface of the active material layer 120 facing away from the current collector 110 has a first edge 1213 and a second edge 1214 that are relatively set in the width direction Y of the electrode 100, and the convex area 121 has a first boundary 1215 and a second boundary 1216 that are relatively set in the width direction Y of the electrode 100. The surface of the active material layer 120 has a first region 122 located between the first edge 1213 and the first boundary 1215, and the surface of the active material layer 120 has a second region 123 located between the second edge and the second boundary 1216. The surface of the active material layer 120 facing away from the current collector 110 further comprises a head clearance region 124 and a tail clearance region 125. The head clearance region 124 is connected to one end of the bump region 121 in the length direction X of the electrode 100, and the tail clearance region 125 is connected to the other end of the bump region 121 in the length direction X of the electrode 100. No protrusions 200 are provided in the first region 122, the second region 123, the head clearance region 124, or the tail clearance region 125, so that the protrusions 200 avoid the edge of the electrode 100.

[0068] Optionally, as shown in FIG4 , the surface of the active material layer 120 facing away from the current collector 110 further has a tab mounting area 126, the tab mounting area 126 is connected to the convex area 121, and the tab mounting area 126 is spaced apart from the edge of the active material layer 120, and the tab mounting area 126 is also not provided with a convex portion 200. The electrode assembly further includes a tab assembly 400, which is provided in the tab mounting area 126 so that the tab assembly 400 avoids the convex portion 200. For this type of pole piece 100 structure, the tab assembly 400 can be first processed into the pole piece 100 to form the convex portion 200, and then the tab assembly 400 is installed on the pole piece 100. At this time, all the convex portions 200 are formed by bending portions of the current collector 110 and portions of the active material layer 120 toward the same side.

[0069] Optionally, as shown in FIG5 , the surface of the active material layer 120 facing away from the current collector 110 is not provided with a tab mounting area 126 , and the tab assembly 400 partially covers the convex area 121 , wherein at least part of the convex portion 200 is formed by bending portions of the current collector 110 and the active material layer 120 toward the same side. Specifically, the convex portion 200 at the tab assembly 400 is formed by bending portions of the tab assembly 400, the current collector 110, and the active material layer 120 toward the same side, and the convex portion 200 in other areas outside the tab assembly 400 is formed by bending portions of the current collector 110 and the active material layer 120 toward the same side. With this type of pole piece 100 structure, the tab assembly can be installed on the pole piece 100, and then the convex portion 200 can be processed on the pole piece 100.

[0070] The tab assembly 400 includes a metal tab 410 and an insulating protective adhesive 420. The metal tab 410 is made of a metal material with good ductility. After the metal tab 410 and the pole piece 100 are stacked in the thickness direction Z, the protrusion 200 is processed on the metal tab 410 and the pole piece 100. The insulating protective adhesive 420 is made of an insulating material and is provided in the wound electrode body 10 structure corresponding to the tab to prevent lithium deposition at the tab. After the insulating protective adhesive and the pole piece 100 are stacked in the thickness direction Z, the protrusion 200 is processed on the insulating protective adhesive 420 and the pole piece 100.

[0071] Optionally, the puncture resistance of the insulating protective adhesive 420 is P, where P satisfies the following: 7N ≤ P ≤ 12N. For example, P can be 7N, 8N, 9N, 10N, 11N, 12N, or a range consisting of any two thereof. When the puncture resistance P of the insulating protective adhesive 420 is within the range of 7N to 12N, the insulating protective adhesive 420 is not easily punctured during machining of the protrusion 200.

[0072] Optionally, the insulating protective adhesive 420 has an elongation Q, where Q satisfies the following: 60% ≤ Q ≤ 120%. For example, Q can be 60%, 70%, 80%, 90%, 100%, 120%, or a range consisting of any two thereof. When the elongation Q of the insulating protective adhesive 420 is within the range of 60% to 120%, the insulating protective adhesive 420 can be easily deformed along with the pole piece 100 to form the protrusion 200.

[0073] In the embodiment of the present application, the puncture resistance P of the insulating protective adhesive 420 and the elongation Q of the insulating protective adhesive 420 are obtained by the following method:

[0074] Step 1: Prepare five 100mm*100mm standard insulation protection adhesive 420 test samples and stack them. The selected standard insulation protection adhesive 420 test samples should not have obvious flaws or damage.

[0075] Step 2: Place the stacked insulation protection adhesive 420 sample in the chamber of an electronic tensile testing machine, set the temperature in the chamber of the electronic tensile testing machine to room temperature (25°C), and use a clamping fixture to clamp the two opposite edge parts of the stacked multi-layer insulation protection adhesive 420 test sample along a preset direction, and ensure that the insulation protection adhesive 420 test sample is clamped but not over-stretched or deformed.

[0076] Step 3: Install the puncture fixture. Install the customized puncture fixture on the electronic tensile testing machine and place the puncture fixture in the initial position. In the direction of stacking of the multi-layer insulation protection glue 420 test samples, the puncture fixture placed in the initial position is 100 mm away from the top layer of insulation protection glue 420 test sample, and the puncture fixture corresponds to the center area of ​​the insulation protection glue 420 test sample.

[0077] Step 4: Start the test by starting the electronic tensile testing machine and allowing the puncture head of the puncture fixture to penetrate the multi-layer insulation protective adhesive 420 test sample at a set speed of 100 mm / min to perform a puncture test. During the test, record the puncture force when the puncture head of the puncture fixture pierces the multi-layer insulation protective adhesive 420 test sample. This puncture force is the puncture resistance P of the insulation protective adhesive 420.

[0078] In step 4, while the puncture resistance P test is being performed, the pulling speed of each clamping fixture is controlled to 10 mm / min, and the two clamping fixtures are controlled to pull the multi-layer insulation protective adhesive 420 test sample in opposite directions. When the puncture tip of the puncture fixture pierces the multi-layer insulation protective adhesive 420 test sample, the electronic tensile testing machine is stopped and the elongation of the multi-layer insulation protective adhesive 420 is recorded, which is the elongation Q of the insulation protective adhesive 420. Here, elongation Q = (Q1-Q0) / Q0*100%, where Q0 is the length of the multi-layer insulation protective adhesive 420 in the preset direction when unstretched, and Q1 is the length of the multi-layer insulation protective adhesive 420 in the preset direction after stretching.

[0079] Optionally, the thickness of the insulating protective adhesive 420 is W, where W satisfies the following conditions: 16 μm ≤ W ≤ 100 μm. For example, W can be 16 μm, 25 μm, 40 μm, 50 μm, 80 μm, 100 μm, or a range consisting of any two thereof. The thickness W of the insulating protective adhesive 420 is in the range of 16 μm to 100 μm. After the protrusion 200 is processed, the portion of the insulating protective adhesive forming the protrusion 200 still has sufficient thickness to maintain its good insulation stability and provide good protection for the pole piece 100.

[0080] For the convenience of description, the protrusion 200 includes a main protrusion 210 and an auxiliary protrusion 220. As shown in Figure 5, the protrusion 200 at the tab assembly 400 is recorded as the auxiliary protrusion 220, and the protrusions 200 at other areas outside the tab assembly 400 are recorded as the main protrusion 210. The main protrusion 210 is formed by bending part of the current collector 110 and part of the active material layer 120 toward the same side, and the auxiliary protrusion 220 is formed by bending part of the current collector 110, part of the active material layer 120 and part of the tab assembly toward the same side.

[0081] As shown in Figure 6, the part of the current collector 110 used to form the main protrusion 210 is the first substrate 211, the inner surface of the first substrate 211 has a first inner peripheral edge line 2111, the first inner peripheral edge line 2111 has a main circumscribed circle, and the diameter of the main circumscribed circle is r1; the part of the current collector 110 used to form the auxiliary protrusion 220 is the second substrate 212, the inner surface of the second substrate 212 has a second inner peripheral edge line 2121, the second inner peripheral edge line 2121 has an auxiliary circumscribed circle, and the diameter of the auxiliary circumscribed circle is r2, wherein r1 and r2 satisfy: r1≤r2, so that the auxiliary protrusion 220 is smoother in structure relative to the main protrusion 210, it is easy to process the auxiliary protrusion 220, and it is not easy to cause damage to the tab assembly 400.

[0082] Optionally, 0.3 mm ≤ r1 ≤ 10 mm. For example, r1 can be 0.3 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, or any two thereof. Within the above range, the first substrate 211 has good structural stability and can provide support for the active material layer 120 to prevent damage to the active material layer 120.

[0083] Optionally, 0.3 mm ≤ r2 ≤ 10 mm. For example, r2 can be 0.3 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, or any two thereof. Within the above range, the second substrate 212 also has good structural stability, can provide support for the active material layer 120, and can prevent damage to the active material layer 120 when the second substrate 212 and the tab assembly act together on the active material layer 120.

[0084] As shown in FIG6 , the inner surface 221 of the main protrusion 210 has a first predetermined spherical diameter SD11, which is the diameter of a first inscribed sphere within the inner surface of the main protrusion 210. The inner surface 221 of the auxiliary protrusion 220 has a second predetermined spherical diameter SD12, which is the diameter of a second inscribed sphere within the inner surface of the auxiliary protrusion 220. The predetermined spherical diameter SD1 includes the first predetermined spherical diameter SD11 and the second predetermined spherical diameter SD12. SD11 ≤ SD12, so that both the main protrusion 210 and the auxiliary protrusion 220 have good structural stability and are not susceptible to deformation while meeting the support height and support area requirements. For example, the tab assembly 400 is installed on the straight section 101, and the heights of the protrusions 200 in the same winding unit are the same, and SD11≤SD12 is set. At the same support height, the first inner diameter R of the inner surface 221 of the main protrusion 210 is smaller than the first inner diameter R of the inner surface of the auxiliary protrusion 220, so that the structure of the auxiliary protrusion 220 is smoother, which facilitates the bending of the current collector 110, the active material layer 120 and the tab assembly together to form the auxiliary protrusion 220.

[0085] Optionally, 2mm≤SD11≤10mm. For example, SD11 may be 2mm, 4mm, 6mm, 8mm, 10mm, or a range consisting of any two thereof.

[0086] Optionally, 10 mm ≤ SD12 ≤ 30 mm. For example, SD12 may be 10 mm, 12 mm, 18 mm, 20 mm, 10 mm, or a range consisting of any two thereof.

[0087] As shown in Figure 5, the head avoidance area 124 and the tail avoidance area 125 are arranged at opposite ends of the convex area 121 in the winding direction of the pole piece 100, and the convex area 121 includes a first convex area 1211 and a second convex area 1212. The first convex area 1211 and the second convex area 1212 are arranged side by side in a direction perpendicular to the winding direction of the pole piece 100, that is, when the pole piece 100 is in the unfolded state, the first convex area 1211 and the second convex area 1212 are arranged side by side in the width direction Y of the pole piece 100, and the first convex area 1211 and the second convex area 1212 extend in the winding direction of the pole piece 100 to connect to the head avoidance area 124 and the tail avoidance area 125 respectively. The tab assembly 400 is disposed in the first bump region 1211 , and the auxiliary protrusions 220 are located in the first bump region 1211 . At this time, a portion of the main protrusions 210 are located in the first bump region 1211 , and another portion of the main protrusions 210 are located in the second bump region 1212 .

[0088] Optionally, at least one of the inner surface and the outer surface of the main protrusion 210 and the auxiliary protrusion 220 located in the first protrusion region 1211 has the same size to facilitate processing. For example, a roller of the first specification is used to correspond to the first bump area 1211, and rolling is performed along the length direction X of the pole piece 100, and an auxiliary protrusion 220 and a part of the main protrusion 210 are processed in the first bump area 1211. At this time, the inner surface dimensions of the main protrusion 210 and the auxiliary protrusion 220 located in the first bump area 1211 are the same. Due to the presence of the tab assembly 200, the outer surface dimension of the auxiliary protrusion 220 located in the first bump area 1211 may be larger than the outer surface dimension of the main protrusion 210 located in the first bump area 1211; a roller of the second specification is used to correspond to the second bump area 1212, and rolling is performed along the length direction X of the pole piece 100, and another part of the main protrusion 210 is processed in the second bump area 1212. At this time, the dimension of the main protrusion 210 located in the first bump area 1211 is greater than or equal to the dimension of the main protrusion 210 located in the second bump area 1212.

[0089] As shown in FIG5 , when the size of the auxiliary protrusion 220 is greater than or equal to that of the main protrusion 210, especially when the size of the auxiliary protrusion 220 is greater than that of the main protrusion 210, the distance between the tab assembly 400 and the main protrusion 210 is too close, which can easily cause rolling stress to squeeze the tab assembly 400 and nearby structures, causing deformation. Based on this, the main protrusion 210 is spaced apart from the tab assembly 400 to reduce the impact of the main protrusion 210 on the installation stability of the tab assembly 400. The outer surface of the main protrusion 210 has a protrusion edge line 2202. The minimum spacing between the tab assembly 400 and the protrusion edge line 2202 of the main protrusion 210 is T2, and T2 satisfies: 0.5 mm ≤ T2 ≤ 30 mm. For example, T2 can be 0.5 mm, 5 mm, 10 mm, 20 mm, 30 mm, or a range consisting of any two thereof.

[0090] In the embodiments of the present application, the tab provided on the positive electrode sheet is referred to as the positive tab, and the tab provided on the negative electrode sheet is referred to as the negative tab. In the embodiments of the present application, there are no particular limitations on the positive electrode sheet, negative electrode sheet, separator 13, positive tab, and negative tab. Any component that can be used as an electrode assembly as is known in the art is applicable to the present application.

[0091] In some exemplary embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. Exemplarily, the negative electrode current collector may be at least one of copper foil, aluminum foil, nickel foil, or a carbon-based current collector; the thickness of the negative electrode current collector may be 1 μm to 200 μm. The negative electrode active material layer may be disposed on one surface or two opposing surfaces of the negative electrode current collector. Furthermore, the negative electrode active material layer may be coated only on a portion of the negative electrode current collector along the thickness direction of the negative electrode sheet. Exemplarily, the thickness of the negative electrode active material layer may be 10 μm to 500 μm.

[0092] The negative electrode active material layer includes a negative electrode active material. Exemplarily, the negative electrode active material includes at least one of lithium metal, natural graphite, artificial graphite, or a silicon-based material. The silicon-based material includes at least one of silicon, a silicon oxide compound, a silicon carbon compound, or a silicon alloy. The negative electrode active material layer may further include a conductive agent and / or a binder. Exemplarily, the conductive agent in the negative electrode active material layer may include at least one of carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes, carbon fibers, or carbon nanowires. The binder in the negative electrode active material layer may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyacrylic acid salt, polyacrylate, polyvinyl pyrrolidone, polyaniline, polyimide, polyamide-imide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

[0093] In some exemplary embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. For example, the positive electrode current collector may be made of aluminum foil, although other commonly used positive electrode current collectors in the art may also be used. The thickness of the positive electrode current collector may be 1 μm to 200 μm. The positive electrode active material layer may be disposed on one surface or two opposing surfaces of the positive electrode current collector. Furthermore, in the thickness direction of the positive electrode sheet, the positive electrode active material layer may be coated only on a portion of the positive electrode current collector. The thickness of the positive electrode active material layer may be 10 μm to 500 μm.

[0094] The positive electrode active material layer includes positive electrode active materials, and the positive electrode active materials include LiCoO2, LiNiO2, LiMn2O4, LiCo 1-y MyO2、LiNi 1-y MyO2、LiMn 2-y MyO4、LiNi x Co y Mn z M 1-x-y-z O2, wherein M is selected from at least one of Fe, Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, or Ti, and 0≤y≤1, 0≤x≤1, 0≤z≤1, and x+y+z≤1. For example, the positive electrode active material may include at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum oxide, or lithium nickel manganate. The positive electrode active material may be doped and / or coated. The positive electrode active material layer further includes a binder and a conductive agent. Illustratively, the binder in the positive electrode active material layer may include at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene; the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, acetylene black, Ketjen black, flake graphite, graphene, carbon nanotubes or carbon fibers.

[0095] In some exemplary embodiments, separator 13 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid. For example, polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene. Polyethylene and polypropylene are particularly effective in preventing short circuits and can improve the stability of the electrode assembly through a shutdown effect. The thickness of separator 13 ranges from approximately 3 μm to 500 μm.

[0096] The present application also provides a battery comprising a housing and an electrode assembly as described above, the electrode assembly being disposed within the interior space of the housing. The battery also comprises an electrolyte, which fills the interior space of the housing and impregnates the electrode assembly. The present application also does not particularly limit the electrolyte; any material known in the art for use as an electrolyte is suitable for use in the present application.

[0097] The present application will be further described below using an electrode assembly of a lithium-ion battery as an example and in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0098] In each embodiment and comparative example of the present application, lithium-ion batteries were prepared and their performance was tested using the following method:

[0099] 1. Preparation method of lithium-ion battery

[0100] (1) Preparation of positive electrode sheet

[0101] The positive electrode active material, lithium cobalt oxide (LiCoO2), conductive carbon black (conductive agent), and binder, polyvinylidene fluoride (PVDF), were dissolved in an N-methylpyrrolidone (NMP) solution at a weight ratio of 97.9:0.9:1.2 to form a positive electrode slurry. A 9μm aluminum foil was used as the positive electrode current collector. The positive electrode slurry was coated on the positive electrode current collector and dried, cold pressed, and cut to obtain a positive electrode sheet. The compacted density of the positive electrode active material layer of the positive electrode sheet was 4.2g / cm 3 .

[0102] In the following embodiments and comparative examples, the positive electrode plate has a convex point area 121 , a first area 122 , a second area 123 , a head avoidance area 124 and a tail avoidance area 125 .

[0103] (2) Preparation of negative electrode sheet

[0104] The negative electrode active material, artificial graphite, the binder, styrene-butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC), were dissolved in deionized water at a weight ratio of 97.4:1.4:1.2 to form a negative electrode slurry. A 10μm thick copper foil was used as the negative electrode current collector. The negative electrode slurry was coated on the negative electrode current collector, dried, cold pressed, and cut to obtain a negative electrode sheet. The compacted density of the negative electrode active material layer of the negative electrode sheet was 1.8g / cm 3 .

[0105] (3) Preparation of isolation film 13

[0106] The diaphragm substrate is a 5μm thick polyethylene PE. A 2μm thick alumina ceramic layer is coated on one side of the diaphragm substrate. Finally, 2.5mg / 1540.25mm thick alumina is coated on both sides of the diaphragm substrate coated with a single ceramic layer.2 The adhesive polyvinylidene fluoride (PVDF) is dried to form a porous layer. The porosity of the porous layer of the separator 13 is 39%.

[0107] (4) Preparation of electrolyte

[0108] In an environment with a water content of less than 10 ppm, ethylene carbonate (abbreviated as EC), propylene carbonate (abbreviated as PC), diethyl carbonate (abbreviated as DEC), ethyl propionate (abbreviated as EP), and propyl propionate (abbreviated as PP) are mixed uniformly in a mass ratio of 1:1:1:1:1, and then the electrolyte salt LiPF6 is dissolved in the above-mentioned non-aqueous solvent. After uniform mixing, an electrolyte is formed, wherein the mass percentage of LiPF6 based on the mass of the electrolyte is 12.5%.

[0109] (5) Assembly of lithium-ion electronics

[0110] Insulating protective adhesive is applied to the first bump area 1211 of the positive electrode sheet, and the positive tab is mounted on the first bump area 1211 of the positive electrode sheet. A first-size roller is used to roll the auxiliary protrusion 220 and a portion of the main protrusion 210 in the first bump area 1211. A second-size roller is used to roll the remaining portion of the main protrusion 210 in the second bump area 1212. The negative tab is mounted on the edge of the negative electrode sheet.

[0111] The positive electrode sheet with the positive tab, the separator 13, and the negative electrode sheet with the negative tab are stacked in sequence, with the separator 13 positioned between the positive and negative electrode sheets to provide isolation. The electrodes are then wound to form the electrode body 10. The electrode assembly is placed in an outer aluminum-plastic film package, dehydrated at 80°C, and then injected with the aforementioned electrolyte and packaged. The lithium-ion battery is then produced through the formation, degassing, and trimming processes. The following describes the testing methods for various parameters of various embodiments of this application.

[0112] 2. Performance test of lithium-ion batteries

[0113] (1) 25℃ / 45℃ cycle test

[0114] In an environment of 25℃ / 45℃, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 / 800 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 / 800 charge and discharge cycles is recorded.

[0115] 25° C. 1C charge / 0.7C discharge cycle capacity retention rate=(discharge capacity at the 1000th cycle / discharge capacity at the first cycle)×100%.

[0116] Cycle capacity retention rate of 45° C. 1C charge / 0.7C discharge=(discharge capacity at the 800th cycle / discharge capacity at the first cycle)×100%.

[0117] (2) Cycling and lithium deposition test

[0118] Normal temperature cycle test: In a 25°C environment, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery is designed for a maximum voltage of 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0119] High-temperature cycling test: In a 45°C environment, the electrode assembly is charged at a constant current of 1C to the full charge voltage (the battery's maximum design voltage is 4.5V). Then, constant voltage charging is performed at the maximum voltage until the current reaches 0.02C. Then, constant current discharge is performed at a discharge current of 0.7C until the final voltage reaches 3.0V. The discharge capacity of the first cycle is recorded. The above steps are then repeated for 1000 charge and discharge cycles. The discharge capacity of the lithium-ion battery after 1000 charge and discharge cycles is recorded.

[0120] After 1000 cycles at 25°C, the battery was disassembled while fully charged to observe whether lithium deposition occurred at the negative electrode interface / protective gel. The degree of lithium deposition was divided into mild and severe. Mild lithium deposition refers to lithium deposition at the interface, and the color of the deposited lithium appears gray or gray-black. Severe lithium deposition appears silvery white at the interface, indicating that the amount of lithium deposition is large and the deposited lithium is relatively dense.

[0121] (3) Winding quality

[0122] After the bare cell winding production is completed, use an X-Ray detector to detect the overhang of the bare cell (the width of the negative electrode edge exceeding the positive electrode edge in the width direction of the positive electrode). If the excess width is greater than 0.2mm, it is a good product. The total number of test samples is 100, and the winding quality rate = number of good products / total number of samples.

[0123] In Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-4, the number of winding turns of the positive electrode sheet is counted, and the protrusion 200 of the positive electrode sheet includes a main protrusion 210 and an auxiliary protrusion 220. In the embodiments of the present application, the main protrusion 210 and the auxiliary protrusion 220 are rolled using the same specification, that is, the first inner diameter R of the inner surface of the main protrusion 210 and the auxiliary protrusion 220 are equal.

[0124] In Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-4, the parameters of the electrode 100 are shown in Table I.

[0125] Table I

[0126] The parameters of L1 / L2, the number of turns of the positive electrode sheet, and the test results of the lithium-ion batteries of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-4 are shown in Table 1.

[0127] Table 1

[0128] According to the experimental results in Table 1, it can be seen that when the number of windings of the positive electrode sheet is an even number, and L1 and L2 satisfy: 1.5≤L1 / L2≤2.2, and when the number of windings of the positive electrode sheet is an odd number, L1 and L2 satisfy: 1.5≤L1 / L2≤2.4, the charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) is improved, and only slight lithium deposition occurs at the negative electrode interface of the lithium-ion battery.

[0129] According to Examples 1-1 to 1-4, 1-8 to 1-9, and Comparative Examples 1-3 to 1-4, it can be seen that when the number of windings of the positive electrode sheet is an even number and the ratio of L1 to L2 exceeds the lower limit of 1.5 or the upper limit of 2.4, the lithium-ion battery has poor charge and discharge cycle performance at room temperature (25°C), and severe lithium deposition occurs at the negative electrode interface of the lithium-ion battery. When the ratio of L1 to L2 is within the range of 1.5-2.2, the charge and discharge cycle performance is better.

[0130] According to Examples 1-5 to 1-7 and Comparative Examples 1-1 to 1-2, it can be seen that the number of windings of the positive electrode sheet is an odd number, the ratio of L1 to L2 exceeds the lower limit of 1.5 or the upper limit of 2.4, the charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) is poor, and severe lithium deposition occurs at the negative electrode interface of the lithium-ion battery.

[0131] The difference between Examples 2-1 to 2-11 and Example 1-2 is that the height H1 of the first convex portion 201 and the height H2 of the second convex portion 202 are different.

[0132] Table 2 shows the parameters of the height H1 of the first protrusion 201 and the height H2 of the second protrusion 202 of Examples 2-1 to 2-11, as well as the test results of the lithium-ion batteries.

[0133] Table 2

[0134] According to the results in Table 2, it can be seen that the height H1 of the first protrusion 201 satisfies 5μm≤H1≤40μm, and the height H2 of the second protrusion 202 satisfies 20μm≤H2≤80μm. The charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) is improved, only slight lithium deposition occurs at the negative electrode interface of the lithium-ion battery, and the winding yield of the electrode assembly is good.

[0135] According to Examples 1-2 and 2-1 to 2-11 in Table 2, it can be seen that the ratio of the height H1 of the first protrusion 201 to the height H2 of the second protrusion 202 satisfies 1.5≤H2 / H1≤5, the charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) is improved, only slight lithium deposition occurs at the negative electrode interface of the lithium-ion battery, and the winding yield of the electrode assembly is good. When the ratio of H1 to H2 is lower than the lower limit of 1.5, the charge and discharge cycle performance of the lithium-ion battery at room temperature (25°C) deteriorates. When the ratio of H1 to H2 is higher than the upper limit of 5, the performance of the lithium-ion battery deteriorates, and the winding yield is reduced.

[0136] The difference between Examples 3-1 to 3-16 and Example 1-2 lies in that the diameter r1 of the main circumscribed circle of the inner surface of the first base 211 of the main protrusion 210, the diameter r2 of the auxiliary circumscribed circle of the inner surface of the second base 212 of the auxiliary protrusion 220, the first preset spherical diameter SD11 of the inner surface of the protrusion 200 and the second preset spherical diameter SD12 of the inner surface of the auxiliary protrusion 220 are different.

[0137] Table 3 shows the parameters of the height H1 of the first protrusion 201 and the height H2 of the second protrusion 202 of Examples 3-1 to 3-16, as well as the test results of the lithium-ion batteries.

[0138] Table 3

[0139] According to the results in Table 3, it can be seen that the diameter r1 of the main circumscribed circle of the inner surface of the first substrate 211 of the main protrusion 210 satisfies 0.3mm≤r1≤10mm, the diameter r2 of the auxiliary circumscribed circle of the inner surface of the second substrate 212 of the auxiliary protrusion 220 satisfies 0.3mm≤r2≤10mm, the first preset spherical diameter SD11 of the inner surface of the main protrusion 210 satisfies 2mm≤SD11≤10mm, and the second preset spherical diameter SD12 of the inner surface of the auxiliary protrusion 220 satisfies 10mm≤SD12≤30mm. The charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is good, and slight lithium deposition occurs at the protective glue, and the winding yield is good.

[0140] According to Examples 1-2, 3-1, and 3-3 in Table 3, it can be seen that when r1 is higher than the upper limit of 10 mm, severe lithium deposition occurs at the protective adhesive. When r1 is lower than the lower limit of 0.3 mm, the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is poor, and the winding yield is low. This is because when r1>10 mm, the height of the main protrusion 210 is low, the support is poor, the improvement in wetting is slight, and lithium deposition occurs at the interface during the cycle. When r1 is less than 0.3 mm, the height difference between the main protrusion 210 and the auxiliary protrusion 220 is too large, and the pole piece 100 tilts in the width direction Y during winding, resulting in poor consistency and low yield. In addition, the large difference in thickness of the electrode body leads to poor interface consistency during the cycle, resulting in uneven lithium ion insertion dynamics, increased polarization, and poor cycle performance.

[0141] According to Examples 3-4 to 3-7 in Table 3, it can be seen that when r2 is higher than the upper limit of 10 mm, severe lithium deposition occurs at the protective glue. When r2 is lower than the lower limit of 0.3 mm, the charge and discharge cycle performance of the lithium-ion battery at 25°C and 45°C is not improved, and the winding yield deteriorates. This is because when r2 is greater than 10 mm, the height of the auxiliary protrusion 220 is small, which fails to achieve the purpose of improving the wetting at the auxiliary protrusion 220, and lithium deposition occurs during the cycle. When r2 is less than 0.3 mm, the height difference between the main protrusion 210 and the auxiliary protrusion 220 is too large, and the pole piece 100 tilts in the width direction Y during winding, resulting in poor consistency and low yield. In addition, such a large difference in the thickness of the electrode body leads to poor interface consistency during the cycle, resulting in uneven lithium ion insertion dynamics, increased polarization, and poor cycle performance.

[0142] According to Examples 3-8 to 3-12 in Table 3, when SD11 is above the upper limit of 10 mm, all performance characteristics of the lithium-ion battery deteriorate. When SD11 is below the lower limit of 2 mm, the charge-discharge cycle performance of the lithium-ion battery at 25°C and 45°C is not improved, and the winding yield deteriorates. This is because when SD11 is greater than 10 mm, the main protrusion 210 is low in height, providing poor support, which does not improve wetting, and severe lithium deposition occurs in the protective adhesive during cycling. When SD11 is less than 2 mm, the height difference between the main protrusion 210 and the auxiliary protrusion 220 is too large, causing the electrode 100 to tilt in the width direction Y during winding, resulting in poor consistency and low yield.

[0143] As can be seen from Examples 3-13 to 3-16 in Table 3, when SD12 exceeds the upper limit of 30 mm, the lithium-ion battery winding yield deteriorates. This is because the height difference between the main protrusion 210 and the auxiliary protrusion 220 is too large, causing the electrode 100 to tilt in the width direction Y during winding, resulting in poor consistency and low yield. When SD12 is below the lower limit of 10 mm, the lithium-ion battery suffers from severe lithium deposition and the winding yield deteriorates. This is because the auxiliary protrusion 220 damages the insulating protective adhesive, causing severe lithium deposition in the corresponding protective adhesive.

[0144] The differences between Examples 4-1 to 4-11, Comparative Examples 5-1 to 4-17 and Example 1-2 are the puncture resistance P of the insulating protective adhesive, the thickness W of the insulating protective adhesive, and the elongation Q of the insulating protective adhesive.

[0145] Table 4 shows the parameters of the puncture strength P, thickness W, and elongation Q of the insulating protective adhesives of Examples 4-1 to 4-17, as well as the test results of lithium-ion batteries.

[0146] Table 4

[0147] According to the experimental results in Table 4, it can be seen that the puncture strength P of the insulating protective adhesive satisfies 7N≤P≤12N, the elongation Q of the insulating protective adhesive satisfies 60%≤Q≤120%, and the thickness W of the insulating protective adhesive satisfies 16μm≤W≤100μm. The charge and discharge cycle performance of the lithium-ion battery at 25°C is improved, and only slight lithium deposition occurs at the protective adhesive.

[0148] According to Examples 4-1 to 4-3 and 4-12 to 4-13 in Table 4, it can be seen that when P is lower than the lower limit of 7N or higher than the upper limit of 12N, the charge and discharge cycle performance of the lithium-ion battery at 25°C deteriorates, and severe lithium deposition occurs at the protective glue.

[0149] It can be seen from Examples 4-4 to 4-7 and 4-13 to 4-15 in Table 4 that when Q is lower than the lower limit of 60% or higher than the upper limit of 120%, the charge and discharge cycle performance of the lithium-ion battery at 25°C deteriorates.

[0150] According to Examples 4-1, 4-8 to 4-11, and 4-16 to 4-17 in Table 4, when W is below the lower limit of 16 μm, the charge-discharge cycle performance of the lithium-ion battery at 25°C deteriorates, and lithium deposition occurs. When W is above the upper limit of 100 μm, the charge-discharge cycle performance of the lithium-ion battery at 25°C deteriorates, and severe lithium deposition occurs in the protective gel.

[0151] The same or similar numbers in the drawings of this embodiment correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0152] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An electrode assembly, the electrode assembly comprising a plurality of electrode tabs and a separator disposed between two of the electrode tabs, wherein at least one of the electrode tabs includes a plurality of protrusions; The electrode tab and the separator are wound multiple times to form a flat electrode body, the electrode body including a straight portion and two corner portions, the straight portion having a first thickness L1 in a first direction, the two corner portions being disposed at opposite ends of the straight portion in a second direction perpendicular to the first direction, the corner portion having a second thickness L2 in the second direction, L1 and L2 satisfying: 1.5 ≤ L1 / L2 ≤ 2.4, each turn of the electrode tab including two straight segments disposed opposite to each other in the first direction and two corner segments disposed at both ends of the straight segment in the second direction; The electrode tab has a finishing end corresponding to the straight segment of the outermost turn of the electrode tab, and all the straight segments and the finishing end stacked in the first direction form the straight portion; the first thickness L1 is the thickness of the straight portion passing through the finishing end in the first direction; All the corner segments located on the same side of the straight segment in the second direction form a corner portion, and the second thickness L2 is the thickness of the corner portion passing through the midpoint of the line connecting the two ends of the innermost corner segment in the second direction.

2. The electrode assembly according to claim 1, wherein, The number of turns of the electrode tab of the electrode body is even, and L1 and L2 satisfy: 1.5 ≤ L1 / L2 ≤ 2.2; or, The number of turns of the electrode tab of the electrode body is odd, and L1 and L2 satisfy: 1.5 ≤ L1 / L2 ≤ 2.

4.

3. The electrode assembly according to claim 1 or 2, wherein The protrusion includes a first protrusion formed on the straight portion and a second protrusion formed on the corner portion, the height of the first protrusion being H1 and the height of the second protrusion being H2, wherein H1 and H2 satisfy: 1.5 ≤ H2 / H1 ≤ 5.

4. The electrode assembly according to claim 3, wherein, H1 satisfies: 5 μm ≤ H1 ≤ 40 μm; and / or, H2 satisfies: 20 μm ≤ H2 ≤ 80 μm.

5. The electrode assembly according to any one of claims 1 to 4, wherein, The inner surface of the protrusion has a preset spherical diameter SD1, and SD1 satisfies: 2 mm ≤ SD1 ≤ 30 mm.

6. The electrode assembly according to any one of claims 1 to 5, wherein, The electrode tab includes a current collector and an active material layer disposed on the surface of the current collector, the surface of the active material layer facing away from the current collector having a bump region, the protrusion being located in the bump region, and the bump region being spaced apart from the edge of the active material layer.

7. The electrode assembly according to claim 6, wherein, The electrode assembly further includes an electrode tab assembly, and a part of the electrode tab assembly covers the bump region; The protrusion includes a main protrusion and an auxiliary protrusion, the main protrusion being formed by bending a part of the current collector and a part of the active material layer towards the same side, and the auxiliary protrusion being formed by bending a part of the current collector, a part of the active material layer, and a part of the electrode tab assembly towards the same side.

8. The electrode assembly according to claim 7, wherein, The part of the current collector for forming the main convex portion is the first substrate. The inner surface of the first substrate has a first inner peripheral edge line, and the first inner peripheral edge line has a main circumscribed circle with a diameter of r1; The part of the current collector for forming the auxiliary convex portion is the second substrate. The inner surface of the second substrate has a second inner peripheral edge line, and the second inner peripheral edge line has an auxiliary circumscribed circle with a diameter of r2; The electrode assembly satisfies at least one of the following conditions: Ⅰ、r1≤r2； Ⅱ. 0.3 mm ≤ r1 ≤ 10 mm; Ⅲ. 0.3 mm ≤ r2 ≤ 10 mm.

9. The electrode assembly according to claim 7, wherein, The inner surface of the main convex portion has a first preset spherical diameter SD11, and the first preset spherical diameter SD11 is the spherical diameter of the first circumscribed sphere where the inner surface of the main convex portion is located; The inner surface of the auxiliary convex portion has a second preset spherical diameter SD12, and the second preset spherical diameter SD12 is the spherical diameter of the second circumscribed sphere where the inner surface of the auxiliary convex portion is located; The electrode assembly satisfies at least one of the following conditions: (1) SD11 ≤ SD12; (2) 2 mm ≤ SD11 ≤ 10 mm; (3) 10 mm ≤ SD12 ≤ 30 mm.

10. The electrode assembly according to claim 7, wherein, The tab assembly is spaced from the main convex portion. The outer surface of the main convex portion has a convex edge line, and the minimum distance between the tab assembly and the convex edge line is T2, and T2 satisfies: 0.5 mm ≤ T2 ≤ 30 mm.

11. The electrode assembly according to claim 7, wherein, The tab assembly includes a metal tab and an insulating protective glue; The insulating protective glue satisfies at least one of the following conditions: a. The puncture resistance of the insulating protective glue is P, and P satisfies: 7 N ≤ P ≤ 12 N; b. The elongation rate of the insulating protective glue is Q, and Q satisfies: 60% ≤ Q ≤ 120%; c. The thickness of the insulating protective glue is W, and W satisfies: 16 μm ≤ W ≤ 100 μm.

12. The electrode assembly according to claim 7, wherein, The surface of the active material layer facing away from the current collector further has a tab mounting area. The tab mounting area is connected to the bump area and is spaced from the edge of the active material layer. The tab assembly is disposed in the tab mounting area to avoid the convex portion.

13. The electrode assembly according to any one of claims 1 to 12, wherein, The convex portion provided on the straight portion protrudes toward the side of the winding center of the electrode body; The convex portion provided on the corner portion protrudes toward the side away from the winding center of the electrode body; Or, the convex portion provided on the corner portion protrudes toward the side of the winding center of the electrode body.

14. A battery, comprising: A housing; And, The electrode assembly according to any one of claims 1 to 13 above, and the electrode assembly is disposed in the internal space of the housing.

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