Electrochemical devices and electronic devices

Abstract

The application provides an electrochemical device and an electronic device. The application sets a first adhesive member on the outermost circle (first pole piece) of an electrode assembly, and the first adhesive member is at least bonded to the first arc-shaped section. The first adhesive member is equal in length to the first pole piece or has an edge along the first direction that exceeds the edge of the first pole piece. The relative position between the first adhesive member and the second adhesive member is adjusted, so that the first adhesive member reinforces the weak area of the arc-shaped section, and can also fix the edge of the first pole piece and has a certain reinforcing effect on the first pole piece. In addition, the first adhesive member has a light weight, and its influence on the energy density of the electrochemical device can be almost ignored. Therefore, the electrochemical device provided by the application has high energy density and improved safety performance.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrochemical device and an electronic device. BACKGROUND

[0002] With the development of intelligent terminal technology, the functions of electronic products are becoming more and more diversified, and the market requirements for the endurance, energy density and safety performance of electrochemical devices (such as lithium ion batteries, etc.) are also increasing year by year. In the use process of the electrochemical device, it is inevitable that the phenomenon of drop impact will occur. When falling, the electrode assembly inside the electrochemical device is stressed, and slippage occurs between the electrode assembly and the shell, which is easy to cause the head and tail of the electrode assembly to collide with the shell, resulting in the extrusion of the pole piece and / or the folding of the separator, which is easy to form a local micro-short circuit to cause capacity attenuation, affecting the user experience. Generally, increasing the thickness of the base material (such as copper foil, aluminum foil and separator, etc.) can improve the safety performance of the soft package type winding electrode assembly, but it will obviously reduce the energy density. SUMMARY

[0003] Therefore, the present application provides an electrochemical device to improve the safety performance without affecting the energy density.

[0004] An embodiment of the present application provides an electrochemical device, which comprises an electrode assembly, a tab and a shell accommodating the electrode assembly. The tab is electrically connected with the electrode assembly and extends out of the shell. The direction in which the tab extends out of the shell is defined as a first direction, and the direction perpendicular to the first direction and the thickness direction of the electrode assembly is defined as a second direction. The electrode assembly comprises a first pole piece, a second pole piece and a separator arranged between the first pole piece and the second pole piece, and the first pole piece, the second pole piece and the separator are arranged in a winding structure. That is, the electrode assembly is in a winding structure. The first pole piece comprises a first current collector and an active material layer arranged on the surface of the first current collector. The outermost circle of the electrode assembly is the first pole piece, and the outermost circle of the first pole piece comprises a first segment, a first arc segment, a second segment and a second arc segment connected in sequence. The electrochemical device further comprises a first adhesive, and the first adhesive at least adheres the first arc segment and extends to the first segment. In the first direction, the first adhesive is equal in length to the first pole piece, or the edge of the first adhesive exceeds the edge of the first pole piece. The electrochemical device further comprises a second adhesive and a third adhesive, the second adhesive adheres the end of the active material layer in the winding direction, and the third adhesive is arranged on the outer surface of the second segment and adheres the shell. The first adhesive at least partially overlaps the second adhesive along the thickness direction of the first pole piece; or the first adhesive does not overlap the second adhesive along the thickness direction of the first pole piece. In the second direction, the width of the electrode assembly is W1; the distance between the winding start end of the second adhesive and the winding end of the first adhesive in the winding direction is W2, and 0 < W2 ≤ 0.15W1.

[0005] By arranging the first adhesive member at the outermost circle (the first tab) of the electrode assembly, and at least bonding the first adhesive member to the first arc-shaped segment, and the edge of the first adhesive member in the first direction exceeding the edge of the first tab, and adjusting the relative position between the first adhesive member and the second adhesive member, the first adhesive member can reinforce the weak area of the arc-shaped segment, and also fix the edge of the first tab and has a certain reinforcing effect on the first tab (the outermost circle of the electrode assembly). Therefore, when mechanical abuse occurs, the first adhesive member can improve the impact resistance of the head and tail of the first tab and the arc-shaped segment, and reduce the probability of sliding between the electrode assembly and the shell, thereby improving the drop resistance of the electrochemical device and improving the safety of the electrochemical device. In addition, compared with the technical solution of increasing the thickness of the base material (such as copper foil, aluminum foil and isolation film), the technical solution of arranging the first adhesive member has almost negligible effect on the energy density of the electrochemical device (the weight of the first adhesive member is relatively light). Therefore, the electrochemical device of the present application has high energy density and improved safety performance.

[0006] In an embodiment, in the first direction, the edge of the first adhesive member does not exceed the edge of the isolation film, so as to improve the drop resistance of the electrochemical device while minimizing the impact on the energy density.

[0007] In an embodiment, 0

[0008] In an embodiment, in the first direction, the first adhesive member has a first edge and a second edge arranged oppositely, and the first tab has a third edge and a fourth edge arranged oppositely. The distance between the first edge and the third edge is L1, and the distance between the second edge and the fourth edge is L2, wherein L1=L2. In this way, the two edges of the first adhesive member uniformly exceed the two edges of the first tab in the first direction, and the first adhesive member simultaneously improves the reinforcement and fixation of the head and tail of the electrode assembly, thereby further improving the drop resistance of the electrochemical device.

[0009] In an embodiment, L1>L2.

[0010] In an embodiment, L1

[0011] In an embodiment, the first adhesive member overlaps the second adhesive member along the thickness direction of the first tab. The overlapping size of the winding start end of the second adhesive member and the winding end of the first adhesive member in the winding direction is W3, and 0

[0012] In one embodiment, the first current collector includes a first surface and a second surface arranged oppositely. The active material layer includes a first active material layer arranged on the first surface and a second active material layer arranged on the second surface. The first active material layer protrudes beyond the second active material layer in a winding direction of the electrode assembly. The first adhesive is arranged on the second surface in a region where the second active material layer is not arranged.

[0013] In one embodiment, the second adhesive includes a first adhesive portion and a second adhesive portion. The first adhesive portion is arranged on the first surface and adheres an end of the first active material layer in the winding direction. The second adhesive portion is arranged on the second surface and adheres an end of the second active material layer in the winding direction. The first adhesive portion and the second adhesive portion can reduce damage to the separator film caused by unevenness or burrs generated at the ends of the active material layers, and can also protect the active material layers from damage and contamination.

[0014] In one embodiment, the electrode assembly includes an arc-shaped region and a flat region connected in sequence in the winding direction. The first segment and the second segment are located in the flat region, and the first arc-shaped segment and the second arc-shaped segment are located in the arc-shaped region. At least one of the first adhesive portion and the second adhesive portion is located in the arc-shaped region.

[0015] In one embodiment, the first tab is a cathode tab, and the second tab is an anode tab. The second tab includes a second current collector. In the winding direction, an end of the second current collector does not protrude beyond an end of the first current collector. The electrode assembly uses the first current collector (cathode current collector) of the first tab as a finishing segment, and the first current collector can increase the hardness of the electrode assembly and protect the electrode assembly.

[0016] In one embodiment, a projection of the first adhesive along a thickness direction of the electrode assembly at least partially overlaps a projection of the third adhesive along the thickness direction of the electrode assembly. In this way, the first adhesive and the second adhesive can synergistically enhance the integrity of the electrode assembly, thereby improving the impact resistance of the electrode assembly.

[0017] One embodiment of the present application provides an electronic device including the electrochemical device described above. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a schematic view of an electrochemical device according to one embodiment of the present application.

[0019] Figure 2 FIG. 2 is a schematic view of the electrochemical device shown in FIG. 1 without a housing. Figure 1 FIG. 3 is a side view of the electrochemical device shown in FIG. 2 without the housing.

[0020] Figure 3 FIG. 4 is a schematic view of an electrode assembly of the electrochemical device shown in FIG. 1 according to one embodiment of the present application. Figure 1

[0021] ​Figure 4 is a schematic view of the electrode assembly of FIG. 1 before winding of the first electrode. Figure 3 Figure 4 (a) of FIG. 1 is a plan view of a first surface of the first electrode tab, Figure 4 (b) of FIG. 1 is a plan view of a second surface of the first electrode tab.

[0022] Figure 5 is a schematic view of the electrode assembly of FIG. 1 in another embodiment. Figure 1

[0023] Figure 6 is a schematic view of the electrode assembly of FIG. 1 in another embodiment. Figure 1

[0024] Figure 7 is a schematic view of an electronic device according to an embodiment of the present application.

[0025] Explanation of Main Element Symbols

[0026] 100: electrochemical device; 10: electrode assembly; 20: tab; 30: case; 40: first adhesive member; 50: second adhesive member; 60: third adhesive member; 70: fourth adhesive member; 80: fifth adhesive member; 11: first electrode tab; 12: second electrode tab; 13: separator; 111: first section; 112: first arc-shaped section; 113: second section; 114: second arc-shaped section; 115: first current collector; 116, 122: active material layer; 101: flat region; 102: arc-shaped region; 1151: first surface; 1152: second surface; 1161: first active material layer; 1162: second active material layer; 121: second current collector; 41: first edge; 42: second edge; 43: third edge; 44: fourth edge; 51: first adhesive portion; 52: second adhesive portion; 200: electronic device; X: first direction; Y: second direction; Z: thickness direction of the electrode assembly; C: winding center axis; D: winding direction.

[0027] The following detailed description will further describe the embodiments of the present application with reference to the above-described drawings. DETAILED DESCRIPTION

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiments of the present application belong. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the present application. Unless otherwise noted, the specific conditions used in the examples are those that are conventional or are those that are indicated to be preferred. The reagents or instruments used are those that are commercially available unless otherwise noted.

[0029] ​​​It should be noted that all directional indications, such as up, down, left, right, front, back, etc., are merely used in the description to facilitate discussion. They are not intended to restrict the scope of the application to a particular orientation.

[0030] It will be understood that when a layer is referred to as being "on" another layer, it can be directly on the other layer or intervening layers can also be present. In contrast, when a layer is referred to as being "directly on" another layer, then there are no intervening layers present. When a component is referred to as being "fixed to", "attached to", "connected to" or "coupled to" another component, it can be directly on the other component or intervening components can also be present.

[0031] Embodiments of the application are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the application. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the application should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. The regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the application.

[0032] Some embodiments of the application will now be described in detail in connection with the accompanying drawings. The following embodiments and features are merely exemplary and are not intended to limit the scope of the application, which is defined by the appended claims. For the purposes of the description and the claims, the following terms take the following meanings.

[0033] Referring to Figures 1 to 3 The first aspect of the application provides an electrochemical device 100. The electrochemical device 100 described in the application includes all devices capable of electrochemical reactions. Specifically, the electrochemical device 100 includes all kinds of primary batteries, secondary batteries, fuel cells, solar cells and capacitors (such as supercapacitors). Optionally, the electrochemical device 100 can be a lithium secondary battery, including lithium metal secondary battery, lithium ion secondary battery, lithium polymer secondary battery and lithium ion polymer secondary battery, etc.

[0034] As Figures 1 to 3As shown, the electrochemical device 100 includes an electrode assembly 10, a tab 20, and a housing 30 housing the electrode assembly 10. The tab 20 is electrically connected to the electrode assembly 10 and extends from the housing 30. The direction in which the tab 20 extends from the housing 30 is defined as a first direction X, and the direction perpendicular to both the first direction X and the thickness direction Z of the electrode assembly 10 (i.e., the thickness direction of the electrochemical device 100) is defined as a second direction Y. The first direction X can be either the length direction or the width direction of the electrode assembly 10. When the first direction X is the length direction of the electrode assembly 10, the second direction Y is the width direction of the electrode assembly 10; when the first direction X is the width direction of the electrode assembly 10, the second direction Y is the length direction of the electrode assembly 10.

[0035] like Figure 3 As shown, the electrode assembly 10 includes a first electrode 11, a second electrode 12, and a separating membrane 13. The separating membrane 13 is disposed between the first electrode 11 and the second electrode 12 to prevent direct contact between the first electrode 11 and the second electrode 12, which could lead to a short circuit. The electrode assembly 10 has a wound structure, that is, the electrode assembly 10 is formed by sequentially stacking and winding the first electrode 11, the separating membrane 13, and the second electrode 12. In this embodiment, as... Figure 3 As shown, the electrode assembly 10 has a winding center axis C perpendicular to the paper surface, and the winding direction D can be... Figure 3 The direction shown is counterclockwise rotation along the central axis C of the winding.

[0036] like Figure 3 As shown, the electrochemical device 100 also includes a first adhesive 40. The outermost ring of the electrode assembly 10 is a first electrode 11, that is, in the electrode assembly 10, on the side of the outermost first electrode 11 away from the center of the electrode assembly 10, there is no other structure (second electrode 12 or separator 13). Along the opposite direction of the winding direction D of the electrode assembly 10 (i.e.,...) Figure 3 (In a clockwise direction), the outermost ring of the first electrode 11 includes a first segment 111, a first arc-shaped segment 112, a second segment 113, and a second arc-shaped segment 114 connected in sequence. The first segment 111 and the second segment 113 are arranged opposite each other, and the first arc-shaped segment 112 and the second arc-shaped segment 114 are arranged opposite each other. The first arc-shaped segment 112 and the second arc-shaped segment 114 are the arc-shaped sections of the outermost ring of the first electrode 11, and the arc-shaped segment can correspond to one or more radii. The first segment 111 and the second segment 113 are the non-arc-shaped sections of the outermost ring of the first electrode 11, and the first segment 111 and the second segment 113 are approximately straight sections. The first adhesive member 40 adheres to at least the first arc-shaped segment 112 and extends to the first segment 111.

[0037] like Figure 3As shown, the electrochemical device 100 further includes a second adhesive member 50 and a third adhesive member 60. The first electrode 11 includes a first current collector 115 and an active material layer 116 disposed on opposite surfaces of the first current collector 115. The second adhesive member 50 adheres to the end of the active material layer 116 along the winding direction D. The third adhesive member 60 is disposed on the outer surface of the second segment 113 and adheres to the housing 30.

[0038] like Figure 4 As shown, along the first direction X, the first adhesive member 40 has a first edge 41 and a second edge 42 disposed opposite to each other, and the first electrode 11 has a third edge 43 and a fourth edge 44 disposed opposite to each other. The first edge 41 is closer to the third edge 43 than the fourth edge 44; the second edge 42 is closer to the fourth edge 44 than the third edge 43. The first edge 41 and the third edge 43 are closer to the position where the electrode tab 20 extends out of the housing 30. Along the first direction X, the first adhesive member 40 is the same length as the first electrode 11, that is, the first edge 41 is flush with the third edge 43, and the second edge 42 is flush with the fourth edge 44. Alternatively, the edge of the first adhesive member 40 extends beyond the edge of the first electrode 11, that is, the first edge 41 of the first adhesive member 40 extends beyond the third edge 43 of the first electrode 11, and / or, the second edge 42 of the first adhesive member 40 extends beyond the fourth edge 44 of the first electrode 11.

[0039] like Figure 3 As shown, in some embodiments, the first adhesive 40 at least partially overlaps with the second adhesive 50 along the thickness direction of the first electrode 11. The thickness direction of the first electrode 11 is not entirely consistent with the thickness direction Z of the electrode assembly 10. Figure 3 As shown, the thickness direction Z of the electrode assembly 10 is in Figure 3 The middle remains unchanged, it has always been Figure 3 The thickness direction of the first electrode 11 changes as it is wound. For example, the thickness direction of the first segment 111 and the second segment 113 of the first electrode 11 is the same as the thickness direction of the electrode assembly 10 (i.e., the thickness direction of the first segment 111 and the second segment 113 is the same as the thickness direction of the electrode assembly 10). Figure 3 (vertical direction in the middle); the first arc segment 112 and the second arc segment 114 of the first electrode 11 have a thickness direction that is not consistent with the thickness direction of the electrode assembly 10.

[0040] like Figure 5 As shown, in some embodiments, the first adhesive 40 does not overlap with the second adhesive 50 along the thickness direction of the first electrode 11. The width of the electrode assembly 10 along the second direction Y is defined as W1. The distance between the starting end of the winding of the second adhesive 50 and the ending end of the winding of the first adhesive 40 along the winding direction D of the electrode assembly 10 is W2, where 0 < W2 ≤ 0.15W1.

[0041] It can be understood that when mechanical abuse occurs (referring to the machine or device being affected by external mechanical force such as collision, extrusion and needle puncture, etc., causing the internal structure to be damaged or the function to be abnormal), the electrode assembly 10 and the shell 30 slip, the head and tail of the electrode assembly 10 (i.e. the two ends of the electrode assembly 10 along the first direction X) are prone to extrusion and short circuit, and the arc-shaped section of the corner of the electrode assembly 10 is a weak area and is prone to deformation and short circuit due to impact. Figure 1

[0042] The present application sets the first adhesive member 40 at the outermost circle of the electrode assembly 10 (the first tab 11), and makes the first adhesive member 40 adhere to at least the first arc-shaped section 112, and the first adhesive member 40 is equal in length to the first tab 11 or the edge of the first adhesive member 40 along the first direction X exceeds the edge of the first tab 11 along the first direction X, and adjusts the relative position between the first adhesive member 40 and the second adhesive member 50, so that the first adhesive member 40 can reinforce the arc-shaped section which is a weak area, and also fix the edge of the first tab 11 and has a certain reinforcing effect on the first tab 11 (the outermost circle of the electrode assembly 10). Therefore, when mechanical abuse occurs, the first adhesive member 40 can improve the impact resistance of the head and tail of the first tab 11 and the arc-shaped section, and can reduce the probability of the electrode assembly 10 slipping with the shell 30, thereby improving the drop resistance of the electrochemical device 100 and improving the safety of the electrochemical device 100. In addition, compared with the technical solution of increasing the thickness of the base material (such as copper foil, aluminum foil and separator film, etc.), the technical solution of setting the first adhesive member 40 in the present application has almost negligible effect on the energy density of the electrochemical device 100 (the first adhesive member 40 is relatively light in weight). Therefore, the electrochemical device 100 of the present application has both high energy density and improved safety performance.

[0043] In some embodiments, along the first direction X, the edge of the first adhesive member 40 does not exceed the edge of the separator film 13. In the electrode assembly 10, the size of the separator film 13 is the largest to better prevent the first tab 11 and the second tab 12 from directly contacting and short circuiting. That is, along the first direction X, the width of the separator film 13 is greater than the width of the first tab 11 and also greater than the width of the second tab 12; along the second direction Y, the length of the separator film 13 is greater than the length of the first tab 11 and also greater than the length of the second tab 12. The edge of the first adhesive member 40 along the first direction X only needs to exceed the edge of the first tab 11 to play its role of improving drop resistance, and does not need to exceed the edge of the separator film 13 to minimize the impact on the energy density of the electrochemical device 100.

[0044] In some embodiments, as shown in FIG. 1, the first adhesive member 40 is a copper foil, and the second adhesive member 50 is an aluminum foil. Figure 4 ​As shown, along the first direction X, the first edge 41 of the first adhesive 40 exceeds the third edge 43 of the first tab 11 by a distance L1, and the second edge 42 of the first adhesive 40 exceeds the fourth edge 44 of the first tab 11 by a distance L2. In this embodiment, L1 = L2. In other embodiments, L1 > L2, or L1 < L2. In some other embodiments, along the first direction X, the first edge 41 of the first adhesive 40 is flush with the third edge 43 of the first tab 11 (L1 = 0), and the second edge 42 of the first adhesive 40 exceeds the fourth edge 44 of the first tab 11 (L2 > 0, i.e. L1 < L2). In some other embodiments, along the first direction X, the first edge 41 of the first adhesive 40 exceeds the third edge 43 of the first tab 11 (L1 > 0), and the second edge 42 of the first adhesive 40 is flush with the fourth edge 44 of the first tab 11 (L2 = 0, i.e. L1 > L2).

[0045] In some embodiments, the first adhesive 40 and the second adhesive 50 are both single-sided tapes.

[0046] In some embodiments, as shown in FIG. 1C, the first adhesive 40 is disposed on the second surface 1152 of the first current collector 115, and the second adhesive 50 is disposed on the first surface 1151 of the first current collector 115. Figure 3 and Figure 4 As shown, the first current collector 115 includes a first surface 1151 and a second surface 1152 oppositely arranged. The active material layer 116 includes a first active material layer 1161 and a second active material layer 1162, the first active material layer 1161 being disposed on the first surface 1151, and the second active material layer 1162 being disposed on the second surface 1152. Along the winding direction D, the first active material layer 1161 exceeds the second active material layer 1162. The first adhesive 40 is disposed on the second surface 1152 in the region where the second active material layer 1162 is not disposed, i.e. the first adhesive 40 is disposed on the empty-foil region of the second surface 1152. In this embodiment, the first surface 1151 is the surface (inner surface) of the first tab 11 facing the center of the electrode assembly 10, and the second surface 1152 is the surface (outer surface) of the first tab 11 facing away from the center of the electrode assembly 10.

[0047] Further, the second adhesive 50 includes a first adhesive portion 51 and a second adhesive portion 52. The first adhesive portion 51 is disposed on the first surface 1151 and adheres to the end of the first active material layer 1161 along the winding direction D. The second adhesive portion 52 is disposed on the second surface 1152 and adheres to the end of the second active material layer 1162 along the winding direction D. At the joint between the active material layer 116 and the first current collector 115, the active material layer 116 can generate unevenness or burrs, which can cause damage to the separator 13 and lead to short circuit. The first adhesive portion 51 and the second adhesive portion 52 can effectively reduce such damage and protect the separator 13. In addition, the first adhesive portion 51 and the second adhesive portion 52 can also protect the active material layer 116 from damage and contamination.

[0048] The first adhesive 40 at least partially overlaps the second adhesive 50 along the thickness direction of the first tab 11, which means that the first adhesive 40 overlaps at least one of the first adhesive portion 51 and the second adhesive portion 52 along the thickness direction of the first tab 11. The first adhesive 40 does not overlap the second adhesive 50 along the thickness direction of the first tab 11, which means that the first adhesive 40 does not overlap either the first adhesive portion 51 or the second adhesive portion 52 along the thickness direction of the first tab 11.

[0049] In some embodiments, as shown in FIG. 1A, the electrode assembly 10 along the winding direction D can include a flat region 101 and an arc region 102 connected in sequence. The arc region 102 is a region in the electrode assembly 10 with an arc-shaped bend on the side surface, and the arc region 102 can correspond to one or more radii. The flat region 101 is a flat section connecting the arc region 102. The first segment 111 and the second segment 113 of the first tab 11 are located in the flat region 101, and the first arc segment 112 and the second arc segment 114 of the first tab 11 are located in the arc region 102. Figure 3 Figure 3 Figure 5 Figure 6 In some embodiments, as shown in FIG. 1A, the first adhesive portion 51 and the second adhesive portion 52 can extend from the flat region 101 to the arc region 102.

[0050] In some embodiments, as shown in FIG. 1A, the first adhesive 40 overlaps the second adhesive 50 along the thickness direction of the first tab 11, and the overlapping size of the winding starting end of the second adhesive 50 and the winding end of the first adhesive 40 along the winding direction D is W3, 0≤W3≤0.15W1. When the overlapping size W3=0, it means that the winding starting end of the second adhesive 50 and the winding end of the first adhesive 40 are just connected, which can also be considered as a special case of overlapping. When W3 is greater than 0.15W1, the effect of improving the drop resistance performance is limited, and there is no need to increase the overlapping size at this time. That is, 0≤W3≤0.15W1, which can not only ensure the effect of improving the drop resistance performance of the electrochemical device 100, but also reduce the impact on the energy density of the electrochemical device 100. Figure 3 Further, as shown in FIG. 1A, when the overlapping region is located in the flat region 101, W3 is the straight-line distance of the overlapping region along the second direction Y. In other embodiments, when the overlapping region is located in the flat region 101 and the arc region 102, W3 is the sum of the straight-line distance of the overlapping region along the second direction Y and the circumference of the arc segment of the overlapping region along the winding direction D.

[0051] Figure 3

[0052] ​​​​​When the first adhesive 40 does not overlap the second adhesive 50 along the thickness direction of the first tab 11, and the winding start end of the second adhesive 50 and the winding end of the first adhesive 40 are both located in the flat area 101, the interval W2 is the straight-line distance between the winding start end of the second adhesive 50 and the winding end of the first adhesive 40 along the second direction Y. When the winding start end of the second adhesive 50 and the winding end of the first adhesive 40 are both located in the arc-shaped area 102, the interval W2 is the circumference of the arc segment formed between the winding start end of the second adhesive 50 and the winding end of the first adhesive 40 along the winding direction D. When one of the winding start end of the second adhesive 50 and the winding end of the first adhesive 40 is located in the arc-shaped area 102, and the other is located in the flat area 101, the interval W2 is the sum of the straight-line distance and the circumference of the arc segment.

[0053] In some embodiments, the first adhesive 40 not only bonds the first segment 111 and the first arc-shaped segment 112, but also bonds the second arc-shaped segment 114. In this way, the first adhesive 40 has a certain protective effect on the exposed surface of the outermost first current collector 115, and can further improve the drop resistance of the electrochemical device 100.

[0054] In some embodiments, as shown in Figure 3 , Figure 5 and Figure 6 , the orthogonal projection of the first adhesive 40 along the thickness direction Z of the electrode assembly 10 at least partially overlaps the orthogonal projection of the third adhesive 60 along the thickness direction Z of the electrode assembly 10. In this way, the first adhesive 40 and the second adhesive 60 can synergistically enhance the integrity of the electrode assembly 10, thereby improving the impact resistance of the electrode assembly 10.

[0055] In some embodiments, the first tab 11 is a cathode tab, and the second tab 12 is an anode tab. The first current collector 115 can be, but is not limited to, an aluminum foil, and the active material layer 116 can include cathode active material, conductive agent, binder, and the like. The cathode active material can be, but is not limited to, lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn2O4), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), lithium iron phosphate (LiFePO4), and the like.

[0056] In some embodiments, as shown in Figure 3 , Figure 5 and Figure 6As shown, the second tab 12 includes a second current collector 121 and an active material layer 122 disposed on opposite surfaces of the second current collector 121. The second current collector 121 can be, but is not limited to, a copper foil, and the active material layer 122 can include an anode active material, a conductive agent, a binder, and the like. The anode active material can be, but is not limited to, a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, a silicon-based material, a tin-based material, lithium titanate, or other metal capable of forming an alloy with lithium, and the like. The graphite can be selected from a combination of one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from a combination of one or more of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon alloy; and the tin-based material can be selected from a combination of one or more of elemental tin, a tin oxide compound, a tin alloy, and the like. In the winding direction D, the end of the second current collector 121 does not extend beyond the end of the first current collector 115. The outermost turn of the electrode assembly 10 is the first tab 11, and the end of the first tab 11 in the winding direction is the end of the first current collector 115. That is, the electrode assembly 10 uses the first current collector 115 (e.g., an aluminum foil) of the first tab 11 as a finishing section, and the first current collector 115 can increase the hardness of the electrode assembly 10 and serve to protect the electrode assembly 10.

[0057] Further, the electrochemical device 100 can further include a fourth adhesive 70. The fourth adhesive 70 is adhered to the end of the first current collector 115 in the winding direction D to fix the finishing first current collector 115, thereby reducing the probability of unrolling of the electrode assembly 10. The end of the fourth adhesive 70 away from the first current collector 115 is adhered to the third adhesive 60, thereby improving the fixing effect on the finishing section of the first current collector 115. The fourth adhesive 70 is a single-sided adhesive, which reduces the friction between the outer surface of the first tab 11 of the outermost turn of the electrode assembly 10 and the case 30, thereby reducing the risk of damage to the first tab 11 of the outermost turn. The third adhesive 60 is a double-sided adhesive, one side of which is adhered to the first current collector 115 and the fourth adhesive 70, and the other side of which is adhered to the case 30, so that the electrode assembly 10 and the case 30 can be relatively fixed. In other embodiments, the fourth adhesive 70 can be omitted, and the third adhesive 60 can be adhered to the end of the first current collector 115 in the winding direction D, thereby fixing the finishing first current collector 115.

[0058] In some embodiments, as shown in FIG. 1A, the first adhesive 40 can extend to cover the third adhesive 60 and then extend to adhere to the end of the first current collector 115 in the winding direction D, thereby further improving the drop resistance. Figure 6

[0059] In some embodiments, as shown in FIG. 1A, the first adhesive 40 can extend to cover the third adhesive 60 and then extend to adhere to the end of the first current collector 115 in the winding direction D, thereby further improving the drop resistance. Figure 2 ​As shown, the electrochemical device 100 can further include a fifth adhesive 80. The fifth adhesive 80 can be arranged at the end of the electrode assembly 10 away from the tab 20, and the fifth adhesive 80 can be wound from one surface of the electrode assembly 10 to the bottom of the electrode assembly 10 (the part where the tab 20 extends out is the head of the electrode assembly 10, and the opposite part is the tail of the electrode assembly 10), and then to the other surface. Therefore, the fifth adhesive 80 is also called a winding adhesive. The fifth adhesive 80 can inhibit the heat absorption expansion of the electrode assembly 10, and can also ensure the stability of the winding structure of the electrode assembly 10, and reduce the probability of unwinding of the electrode assembly 10. The fifth adhesive 80 can be a single-sided adhesive.

[0060] In some embodiments, the separator film 13 can include a porous substrate, which can be, but is not limited to, polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, aramid, etc. In some embodiments, the separator film 13 further includes a coating layer arranged on the porous substrate, and the coating layer includes at least one of a binder and inorganic particles. The binder can be, but is not limited to, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of vinylidene fluoride-trichloroethylene, polyacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, etc., and the inorganic particles can be, but are not limited to, silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, hafnium dioxide, tin oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, magnesium hydroxide, aluminum hydroxide, calcium titanate, barium titanate, lithium phosphate, lithium titanium phosphate, lithium lanthanum titanate, etc.

[0061] In some embodiments, the shell 30 is a packaging bag obtained by packaging with a packaging film (such as an aluminum plastic film), i.e., the electrochemical device 100 can be a soft package battery. In other embodiments, the electrochemical device 100 can also be a steel shell battery or an aluminum shell battery.

[0062] In some embodiments, the electrochemical device 100 further includes an electrolyte (not shown in the figure), and the electrolyte includes a solvent and a lithium salt. The solvent can be, but is not limited to, one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, vinyl carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, vinylene carbonate, propylene sulfite. The lithium salt can be, but is not limited to, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethyl sulfonate.

[0063] Please refer to Figure 7 The second aspect of the present application provides an electronic device 200, which includes the electrochemical device 100 as described above. Exemplarily, the electronic device 200 can be a mobile phone. In other embodiments, the electronic device 200 can also be a notebook computer, a drone, a camera, an energy storage device, etc.

[0064] The present application will be further described below in conjunction with specific embodiments and comparative examples.

[0065] Example 1

[0066] (1) Preparation of the first electrode sheet (cathode electrode sheet)

[0067] Cathode active material lithium cobaltate (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5, N-methylpyrrolidone (NMP) was added as a solvent, and a slurry having a solid content of 0.75 was prepared and stirred uniformly. The slurry was uniformly coated on an aluminum foil (first current collector) so that the weight of the cathode active material on the electrode sheet was 180 g / m 2 . Drying at 90°C was performed, and thus one-side coating of the electrode sheet was completed. The other side was coated in the same manner. After the coating was completed, the cathode active material layer of the electrode sheet was cold-pressed to a compact density of 4.0 g / cm 3 . Subsequently, tab welding and attachment of the first adhesive, the second adhesive, the third adhesive, the fourth adhesive, and other auxiliary processes were performed, and thus the entire preparation process of the first electrode sheet was completed.

[0068] (2) Preparation of the second electrode sheet (anode electrode sheet)

[0069] Anode active material graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, deionized water (H2O) was added as a solvent, and a slurry having a solid content of 0.7 was prepared and stirred uniformly. The slurry was uniformly coated on a copper foil (second current collector) so that the weight of the anode active material on the electrode sheet was 95 g / m 2 . Drying at 110°C was performed, and thus one-side coating of the electrode sheet was completed. The other side was coated in the same manner. After the coating was completed, the anode active material layer of the electrode sheet was cold-pressed to a compact density of 1.7 g / cm 3 . Subsequently, tab welding and attachment of the adhesive (adhesive tape) and other auxiliary processes were performed, and thus the entire preparation process of the second electrode sheet was completed.

[0070] (3) Preparation of the electrolyte

[0071] In a dry argon atmosphere, first, organic solvents ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of EC:EMC:DEC = 30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF6) was added to the organic solvents to be dissolved and mixed uniformly, and thus an electrolyte having a lithium salt concentration of 1.15 M was obtained.

[0072] (4) Preparation of the electrochemical device (lithium ion battery)

[0073] Polyethylene (PE) with a thickness of 15μm was selected as the separator. The prepared first electrode, separator and second electrode were stacked in sequence, and then the stacked electrode and separator were wound to obtain the electrode assembly.

[0074] The electrode assembly is placed in a housing (aluminum-plastic film), electrolyte is injected, and the device is sealed to obtain an electrochemical device.

[0075] In this embodiment, the electrode assembly has a length of 90.0 mm along the first direction X, a width W1 of 34.0 mm along the second direction Y, and a thickness of 5.0 mm. The first electrode sheet has a length of 82.7 mm along the first direction X. The first adhesive member has a length of 86.7 mm along the first direction X, with its first edge (upper edge) extending beyond the third edge (upper edge) of the first electrode sheet by L1 = 2 mm, and its second edge (lower edge) extending beyond the fourth edge (lower edge) of the first electrode sheet by L2 = 2 mm. The thickness of the first adhesive member is 16 μm. The first adhesive portions of the first adhesive member and the second adhesive member do not overlap (e.g., ...). Figure 5 As shown), the distance W2 between the winding end of the first adhesive and the winding start end of the first adhesive portion of the second adhesive is 5.1 mm (i.e., 0.15W1).

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that the distance W2 between the winding end of the first adhesive component and the winding start end of the first adhesive portion of the second adhesive component is 3.0 mm. All other aspects are the same as in Example 1 and will not be repeated here.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that the distance W2 between the winding end of the first adhesive component and the winding start end of the first adhesive portion of the second adhesive component is 1.0 mm. Everything else is the same as in Example 1, and will not be repeated here.

[0080] Example 4

[0081] The difference between Example 4 and Example 1 is that the first adhesive portion of the first adhesive component and the first adhesive portion of the second adhesive component exactly overlap, and W3 is 0 mm. Everything else is the same as in Example 1, and will not be repeated here.

[0082] Example 5

[0083] The difference between Example 5 and Example 1 is that the first adhesive portion of the first adhesive component overlaps with the first adhesive portion of the second adhesive component (e.g., ...). Figure 3 As shown in the figure, the overlap dimension W3 is 1.0 mm. The rest are the same as in Example 1, and will not be repeated here.

[0084] Example 6

[0085] Example 6 differs from Example 5 in that the overlap dimension W3 is 2.0 mm. The rest is the same as Example 5, which will not be repeated here.

[0086] Example 7

[0087] Example 7 differs from Example 5 in that the overlap dimension W3 is 5.1 mm. The rest is the same as Example 5, which will not be repeated here.

[0088] Example 8

[0089] Example 8 differs from Example 6 in that L1 = 0.0 mm, L2 = 0 mm. The rest is the same as Example 6, which will not be repeated here.

[0090] Example 9

[0091] Example 9 differs from Example 6 in that L2 = 0 mm. The rest is the same as Example 6, which will not be repeated here.

[0092] Example 10

[0093] Example 10 differs from Example 6 in that L1 = 0 mm. The rest is the same as Example 6, which will not be repeated here.

[0094] Example 11

[0095] Example 11 differs from Example 6 in that L1 = 1.0 mm, L2 = 1.0 mm. The rest is the same as Example 6, which will not be repeated here.

[0096] Example 12

[0097] Example 12 differs from Example 6 in that the bottom of the electrode assembly is provided with a fifth adhesive (i.e. a wrap-around adhesive, as shown in Figure 2 The rest is the same as Example 6, which will not be repeated here.

[0098] Comparative Example 1

[0099] Comparative Example 1 differs from Example 1 in that the first adhesive is not provided. The rest is the same as Example 1, which will not be repeated here.

[0100] Comparative Example 2

[0101] Comparative Example 2 differs from Example 1 in that the first edge of the first adhesive member is inwardly recessed by 1.0 mm from the third edge of the first electrode tab (i.e., L1 = -1.0 mm), and the second edge is inwardly recessed by 1.0 mm from the fourth edge of the first electrode tab (i.e., L2 = -1.0 mm); the distance W2 between the winding start end of the first adhesive portion of the second adhesive member and the winding end of the first adhesive member is 6.0 mm, which exceeds 0.15W1 (5.10 mm). The rest is the same as Example 1, which will not be repeated here.

[0102] Comparative Example 3

[0103] Comparative Example 3 differs from Example 1 in that L1 = 0 mm, L2 = 0 mm, and the distance W2 between the winding start end of the first adhesive portion of the second adhesive member and the winding end of the first adhesive member is 6.0 mm, which exceeds 0.15W1 (5.10 mm). The rest is the same as Example 1, which will not be repeated here.

[0104] Five of each of the electrochemical devices in Examples 1-12 and Comparative Examples 1-3 were selected for numbering, and the voltage before dropping was tested, then the dropping test was performed, and the voltage after dropping was tested, and finally the average voltage drop of the five electrochemical devices in each example and comparative example was calculated, which was recorded as the voltage drop of the example or comparative example. If the tested electrochemical device does not catch fire, does not explode, does not smoke, does not leak, and the voltage drop before and after the test is less than 30 mV, it is considered to pass the dropping test.

[0105] The specific steps of the dropping test are as follows. Each electrochemical device is loaded into a dropping fixture and fixed on one side using double-sided tape. In a test environment of 25±5℃, using a marble dropping floor, the electrochemical device is dropped from a dropping height of 1.5 m along each of its six surfaces for one time, and four corners for one time, for a total of five rounds of testing. The voltage of the electrochemical device is tested at 24 h after the test.

[0106] The parameter settings of each example and comparative example and the voltage drop data of the dropping test are shown in Table 1.

[0107] Table 1

[0108]

[0109]

[0110] From the data in Table 1, it can be seen that the pressure drop of the electrochemical devices in Examples 1-12 is controlled within 30 mV, and after the drop test, none of the electrochemical devices catch fire, explode, smoke or leak, and all pass the drop test. In Comparative Examples 1-3, the voltage drop of the electrochemical devices is far more than 30 mV, and the electrochemical devices in Comparative Examples 1-3 do not pass the drop test. This shows that the first adhesive member of the present application can improve the drop resistance of the electrochemical device.

[0111] From the comparison of Examples 1-3 and Examples 4-7, it can be seen that the voltage drop in Examples 4-7 is lower than that in Examples 1-3, which shows that the effect of the overlap of the first adhesive member and the second adhesive member is better than that of no overlap of the first adhesive member and the second adhesive member. From Examples 1-3, it can be seen that the smaller the distance W2 between the first adhesive member and the second adhesive member, the more helpful it is to reduce the voltage drop. From Examples 4-7, it can be seen that within a certain range, increasing the size W3 of the overlap helps to reduce the voltage drop, thereby improving the safety performance of the electrochemical device.

[0112] From Examples 8-11, it can be seen that when the edges of the first adhesive member exceed the edges of the first electrode plate (at least one of L1 and L2 is greater than 0), the voltage drop is slightly lower than that when the edges of the first adhesive member are flush with the edges of the first electrode plate (L1 and L2 are both 0). Further, in Examples 8-11, when both edges of the first adhesive member uniformly exceed both edges of the first electrode plate, the voltage drop is the smallest (Example 11); when only one edge of the first adhesive member exceeds the edge of the first electrode plate, the voltage drop is the second (Examples 9 and 10), and the effect of the first edge exceeding the third edge is basically equivalent to that of the second edge exceeding the fourth edge; when both edges of the first adhesive member are flush with both edges of the first electrode plate, the voltage drop is the largest (Example 8).

[0113] From the comparison of Example 6, Example 8 and Example 11, it can be seen that within a certain range, increasing the size of L1 and L2 helps to reduce the voltage drop. From Example 6 and Example 12, it can be seen that the voltage drop of Example 12 provided with the winding glue is slightly higher than that of Example 6 without the winding glue. This is because when the edges of the first adhesive member exceed the edges of the first electrode plate, the first adhesive member can interfere with the winding glue at the bottom, thereby affecting the voltage drop and the drop performance.

[0114] As can be seen from the comparison between Comparative Example 1 and Comparative Example 2 and Comparative Example 3, although the distance W2 (6.0 mm) between the first adhesive member and the second adhesive member in Comparative Example 2 exceeds the range of 0.15W1 (5.10 mm) and the edge of the first adhesive member is recessed, and the distance W2 (6.0 mm) between the first adhesive member and the second adhesive member in Comparative Example 3 exceeds the range of 0.15W1 (5.10 mm), the pressure drop of Comparative Example 2 and Comparative Example 3 is still lower than that of Comparative Example 1, indicating that as long as the first adhesive member is provided, the drop resistance performance can be improved to a certain extent. If the optimal effect is to be achieved, the structure and position of the first adhesive member also need to be optimized.

[0115] The electrochemical device 100 and the electronic device 200 of the embodiments of the present application can improve the drop resistance performance of the electrochemical device 100 and the electronic device 200 by providing the first adhesive member 40 at the outermost circle (the first tab 11) of the electrode assembly 10, bonding the first adhesive member 40 to at least the first arc-shaped section 112, making the first adhesive member 40 equal in length to the first tab 11 or having an edge along the first direction X that exceeds the edge of the first tab 11, and adjusting the relative position between the first adhesive member 40 and the second adhesive member 50 so that the first adhesive member 40 reinforces the arc-shaped section which is a weak area and also fixes the edge of the first tab 11 and has a certain reinforcing effect on the first tab 11. Therefore, when mechanical abuse occurs, the first adhesive member 40 can improve the impact resistance of the head and tail of the first tab 11 and the arc-shaped section, and can reduce the probability of slippage between the electrode assembly 10 and the case 30, thereby improving the drop resistance performance of the electrochemical device 100 and improving the safety of the electrochemical device 100. In addition, the first adhesive member 40 has a relatively light weight, and its effect on the energy density of the electrochemical device 100 can be almost negligible. Therefore, the electrochemical device 100 of the present application has both a high energy density and improved safety performance.

[0116] The above description is some specific embodiments of the present application, but in actual application process, it cannot be limited to these embodiments. Other modifications and changes made by those skilled in the art according to the technical concept of the present application should all belong to the protection scope of the present application.

Claims

1. An electrochemical device, characterized in that, The electrochemical device includes an electrode assembly, tabs, and a housing containing the electrode assembly; the tabs are electrically connected to the electrode assembly and extend from the housing, and the direction in which the tabs extend from the housing is defined as a first direction; the electrode assembly includes a first electrode, a second electrode, and a separating membrane disposed between the first electrode and the second electrode, and the electrode assembly has a wound structure; The electrochemical device further includes a first adhesive component, the outermost ring of the electrode assembly is the first electrode sheet, the outermost ring of the first electrode sheet includes a first segment, a first arc segment, a second segment and a second arc segment connected in sequence, and the first adhesive component is at least bonded to the first arc segment and extends to the first segment; Along the first direction, the first adhesive member is the same length as the first electrode sheet, or the edge of the first adhesive member extends beyond the edge of the first electrode sheet; The electrochemical device further includes a second adhesive and a third adhesive. The first electrode includes a first current collector and an active material layer disposed on the surface of the first current collector. The second adhesive is bonded to the end of the active material layer along the winding direction. The third adhesive is disposed on the outer surface of the second segment and is bonded to the housing. The first adhesive member overlaps at least partially with the second adhesive member along the thickness direction of the first electrode sheet; or, The first adhesive does not overlap with the second adhesive along the thickness direction of the first electrode sheet; Along the second direction, the width of the electrode assembly is W1; the distance between the winding start end of the second adhesive and the winding end of the first adhesive along the winding direction of the electrode assembly is W2, 0 < W2 ≤ 0.15W1; wherein, the second direction is perpendicular to the first direction and the thickness direction of the electrode assembly.

2. The electrochemical device as described in claim 1, characterized in that, Along the first direction, the edge of the first adhesive does not extend beyond the edge of the release membrane.

3. The electrochemical device as described in claim 2, characterized in that, 0 < W2 ≤ 0.09W1.

4. The electrochemical device as described in claim 2, characterized in that, Along the first direction, the first adhesive has a first edge and a second edge disposed opposite to each other, and the first electrode has a third edge and a fourth edge disposed opposite to each other. The distance by which the first edge extends beyond the third edge is L1, and the distance by which the second edge extends beyond the fourth edge is L2, wherein L1 > L2 or L1 < L2.

5. The electrochemical device as described in claim 1, characterized in that, The first adhesive overlaps with the second adhesive along the thickness direction of the first electrode sheet, and the overlap dimension between the winding start end of the second adhesive and the winding end of the first adhesive along the winding direction is W3, where 0≤W3≤0.15W1.

6. The electrochemical device as claimed in claim 1, characterized in that, The first current collector includes a first surface and a second surface disposed opposite to each other, and the active material layer includes a first active material layer disposed on the first surface and a second active material layer disposed on the second surface; Along the winding direction of the electrode assembly, the first active material layer extends beyond the second active material layer; The first adhesive is disposed on the area of ​​the second surface where the second active material layer is not provided.

7. The electrochemical device as described in claim 6, characterized in that, The second adhesive includes a first adhesive portion and a second adhesive portion. The first adhesive portion is disposed on the first surface and adheres to the end of the first active material layer along the winding direction. The second adhesive portion is disposed on the second surface and adheres to the end of the second active material layer along the winding direction.

8. The electrochemical device as described in claim 7, characterized in that, Along the winding direction, the electrode assembly includes a sequentially connected arc-shaped region and a straight region, the first segment and the second segment being located in the straight region, the first arc-shaped segment and the second arc-shaped segment being located in the arc-shaped region, and at least one of the first adhesive portion and the second adhesive portion being located in the arc-shaped region.

9. The electrochemical device as claimed in claim 1, characterized in that, The second electrode includes a second current collector, and along the winding direction, the end of the second current collector does not extend beyond the end of the first current collector.

10. The electrochemical device as claimed in claim 1, characterized in that, The orthographic projection of the first adhesive member along the thickness direction of the electrode assembly at least partially overlaps with the orthographic projection of the third adhesive member along the thickness direction of the electrode assembly.

11. The electrochemical device as claimed in claim 1, characterized in that, The first electrode is a cathode electrode, and the second electrode is an anode electrode.

12. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 1 to 11.

Images