Electrochemical device and electronic device

Abstract

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

Description

Technical Field

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

[0002] With the development of smart terminal technology, the functions of electronic products have become more and more diversified, and the market's requirements for the endurance, energy density, and safety performance of electrochemical devices (such as lithium-ion batteries, etc.) have also increased year by year. During the use of electrochemical devices, the phenomenon of drop impact is inevitable. When dropping, the electrode assembly inside the electrochemical device is stressed and slips relative to the housing, which easily causes the head and tail of the electrode assembly to impact the housing, resulting in the pole piece being squeezed and / or the separator being folded, which is very likely to form a local micro short circuit and cause capacity attenuation, affecting the user experience. Generally, increasing the thickness of the base materials (such as copper foil, aluminum foil, and separator, etc.) can improve the safety performance of the soft-packaged wound electrode assembly, but it significantly reduces the energy density. Summary of the Invention

[0003] In view of this, the present application proposes an electrochemical device to improve its safety performance without affecting the energy density.

[0004] An embodiment of the present application provides an electrochemical device, including an electrode assembly, a tab, and a housing for receiving the electrode assembly. The tab is electrically connected to the electrode assembly and extends out of the housing. Define the direction in which the tab extends out of the housing as the first direction, and the direction perpendicular to both the first direction and the thickness direction of the electrode assembly as the second direction. The electrode assembly includes a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, and the first pole piece, the second pole piece, and the separator are wound. That is, the electrode assembly is a wound structure. The first pole piece includes a first current collector and an active material layer disposed on the surface of the first current collector. The outermost layer of the electrode assembly is the first pole piece, and the outermost layer of the first pole piece includes a first section, a first arc section, a second section, and a second arc section connected in sequence. The electrochemical device further includes a first bonding member that bonds at least the first arc section and extends to the first section. Along the first direction, the first bonding member is as long as the first pole piece, or the edge of the first bonding member extends beyond the edge of the first pole piece. The electrochemical device further includes a second bonding member and a third bonding member. The second bonding member bonds the end of the active material layer along the winding direction, and the third bonding member is disposed on the outer surface of the second section and bonds the housing. The first bonding member at least partially overlaps the second bonding member along the thickness direction of the first pole piece; or the first bonding member does not overlap the second bonding member along the thickness direction of the first pole piece. Along the second direction, the width of the electrode assembly is W 1 ; the distance between the winding start end of the second bonding member and the winding end of the first bonding member along the winding direction is W 2 , 0 < W 2 ≤0.15W 1 .

[0005] By providing a first bonding member at the outermost circumference (first electrode tab) of the electrode assembly, and causing the first bonding member to bond at least to the first arc segment, and the edge of the first bonding member in the first direction to extend beyond the edge of the first electrode tab, and adjusting the relative position between the first bonding member and the second bonding member, the first bonding member can reinforce the weak area of the arc segment, can also fix the edge of the first electrode tab and has a certain reinforcing effect on the first electrode tab (the outermost circumference of the electrode assembly). Therefore, when mechanical abuse occurs, the first bonding member can improve the impact resistance of the head and tail of the first electrode tab and the arc segment, and can reduce the probability of slippage between the electrode assembly and the housing, thereby improving the drop resistance of the electrochemical device and enhancing 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 separator), the technical solution of providing the first bonding member in this application has almost negligible impact on the energy density of the electrochemical device (the first bonding member is light in weight). Therefore, the electrochemical device of this application has both a high energy density and improved safety performance at the same time.

[0006] In one embodiment, along the first direction, the edge of the first bonding member does not extend beyond the edge of the separator, so as to minimize the impact on its energy density while improving the drop resistance of the electrochemical device.

[0007] In one embodiment, 0 < W 2 ≤0.09W 1 .

[0008] In one embodiment, along the first direction, the first bonding member has a first edge and a second edge disposed opposite to each other, and the first electrode tab 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 L 1 , and the distance by which the second edge extends beyond the fourth edge is L 2 , where L 1 = L 2 . Thus, the two edges of the first bonding member in the first direction uniformly extend beyond the two edges of the first electrode tab, and the first bonding member simultaneously improves the reinforcement and fixing effects on the head and tail of the electrode assembly, so that the drop resistance of the electrochemical device can be further improved.

[0009] In one embodiment, L 1 > L 2 .

[0010] In one embodiment, L 1 < L 2 .

[0011] In one embodiment, the first adhesive member overlaps with the second adhesive member along the thickness direction of the first electrode tab. The overlapping dimension W of the winding starting end of the second adhesive member and the winding ending end of the first adhesive member along the winding direction is defined as follows 3 , 0 ≤ W 3 ≤ 0.15W 1 . In this way, both the anti-drop performance of the electrochemical device can be improved and the influence on the energy density can be reduced.

[0012] In one embodiment, the first current collector includes a first surface and a second surface which are oppositely arranged. 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, and the first adhesive member is disposed in the region where the second active material layer is not provided on the second surface.

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

[0014] In one embodiment, along the winding direction, the electrode assembly includes a curved region and a straight region which are connected in sequence. The first segment and the second segment are located in the straight region, and the first curved segment and the second curved segment are located in the curved region. At least one of the first adhesive portion and the second adhesive portion is located in the curved region.

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

[0016] In one embodiment, the orthographic projection of the first adhesive member along the thickness direction of the electrode assembly overlaps at least partially with the orthographic projection of the third adhesive member along the thickness direction of the electrode assembly. In this way, the first adhesive member and the second adhesive member can cooperate to enhance the integrity of the electrode assembly, thereby improving the anti-impact performance of the electrode assembly.

[0017] One embodiment of the present application provides an electronic device, which includes the electrochemical device as described above. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 2 The Figure 1 side view of the electrochemical device shown after removing the housing.

[0020] Figure 3 is Figure 1 schematic diagram of the electrode assembly of the electrochemical device shown in one embodiment.

[0021] Figure 4 is Figure 3 schematic diagram of the first pole of the electrode assembly shown before winding, where Figure 4 (a) is a top view of the first surface of the first pole piece, Figure 4 (b) is a top view of the second surface of the first pole piece.

[0022] Figure 5 is Figure 1 schematic diagram of the electrode assembly of the electrochemical device shown in another embodiment.

[0023] Figure 6 is Figure 1 schematic diagram of the electrode assembly of the electrochemical device shown in another embodiment.

[0024] Figure 7 Schematic diagram of an electronic device according to an embodiment of the present application.

[0025] Description of main element symbols

[0026] 100: Electrochemical device; 10: Electrode assembly; 20: Tab; 30: Housing; 40: First adhesive; 50: Second adhesive; 60: Third adhesive; 70: Fourth adhesive; 80: Fifth adhesive; 11: First pole piece; 12: Second pole piece; 13: Separator; 111: First section; 112: First arc section; 113: Second section; 114: Second arc section; 115: First current collector; 116, 122: Active material layer; 101: Straight region; 102: Arc 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 bonding part; 52: Second bonding part; 200: Electronic device; X: First direction; Y: Second direction; Z: Thickness direction of the electrode assembly; C: Winding central axis; D: Winding direction.

[0027] The following specific embodiments will further illustrate the embodiments of the present application in conjunction with the above drawings. Specific embodiments

[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 technical field to which the embodiments of this application belong. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the embodiments of this application. Those conditions not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments whose manufacturers are not indicated are all conventional products that can be obtained through commercial purchase.

[0029] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of this application are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[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 there can be an intermediate layer therebetween. In contrast, when a layer is referred to as being "directly on" another layer, there is no intermediate layer. When a component is referred to as being "fixed to", "mounted on", "disposed on", "connected to" another component, it can be directly on the other component or there can also be an intermediate component.

[0031] The embodiments of this application are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments (and intermediate structures) of this application. Thus, differences in the shapes shown due to manufacturing processes and / or tolerances are foreseeable. Therefore, the embodiments of this application should not be construed as limited to the specific shapes of the regions shown herein, but should include, for example, deviations in shape due to manufacturing. The regions shown in the figures are merely schematic, their shapes are not intended to illustrate the actual shape of the device, and are not intended to limit the scope of this application.

[0032] The following describes in detail some embodiments of this application with reference to the drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0033] Please refer to Figures 1 to 3 , a first aspect of this application provides an electrochemical device 100. The electrochemical device 100 described in this application includes all devices capable of undergoing 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 batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries, etc.

[0034] As Figures 1 to 3As shown, the electrochemical device 100 includes an electrode assembly 10, a tab 20, and a housing 30 that houses the electrode assembly 10. The tab 20 is electrically connected to the electrode assembly 10 and extends out of the housing 30. The direction in which the tab 20 extends out of the housing 30 is defined as the first direction X, and the direction that is 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 the second direction Y. Among them, the first direction X can be the length direction of the electrode assembly 10 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] As Figure 3 shown, the electrode assembly 10 includes a first electrode tab 11, a second electrode tab 12, and a separator 13. The separator 13 is disposed between the first electrode tab 11 and the second electrode tab 12 to prevent the first electrode tab 11 and the second electrode tab 12 from directly contacting and causing a short circuit. The electrode assembly 10 is a wound structure, that is, the electrode assembly 10 is formed by winding the first electrode tab 11, the separator 13, and the second electrode tab 12 in sequence after being stacked. In this embodiment, as Figure 3 shown, the electrode assembly 10 has a winding central axis C perpendicular to the paper surface, and the winding direction D can be Figure 3 the direction of counterclockwise rotation along the winding central axis C as shown.

[0036] As Figure 3 shown, the electrochemical device 100 further includes a first adhesive member 40. The outermost layer of the electrode assembly 10 is the first electrode tab 11, that is, in the electrode assembly 10, on the side of the outermost first electrode tab 11 away from the center of the electrode assembly 10, there is no presence of other structures (the second electrode tab 12 or the separator 13). Along the reverse direction of the winding direction D of the electrode assembly 10 (i.e., Figure 3 the clockwise direction in

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

[0038] As Figure 4 shown, along the first direction X, the first adhesive member 40 has a first edge 41 and a second edge 42 that are oppositely arranged. The first electrode sheet 11 has a third edge 43 and a fourth edge 44 that are oppositely arranged. Compared with the fourth edge 44, the first edge 41 is closer to the third edge 43; compared with the third edge 43, the second edge 42 is closer to the fourth edge 44. The first edge 41 and the third edge 43 are closer to the position where the 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 sheet 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 sheet 11, that is, the first edge 41 of the first adhesive member 40 extends beyond the third edge 43 of the first electrode sheet 11, and / or the second edge 42 of the first adhesive member 40 extends beyond the fourth edge 44 of the first electrode sheet 11.

[0039] As Figure 3 shown, in some embodiments, the first adhesive member 40 at least partially overlaps with the second adhesive member 50 along the thickness direction of the first electrode sheet 11. The thickness direction of the first electrode sheet 11 is not completely consistent with the thickness direction Z of the electrode assembly 10. As Figure 3 shown, the thickness direction Z of the electrode assembly 10 remains unchanged in Figure 3 and is always the Figure 3 vertical direction in Figure 3 , while the thickness direction of the first electrode sheet 11 changes as the first electrode sheet 11 is wound. For example, for the first section 111 and the second section 113 of the first electrode sheet 11, its thickness direction is the thickness direction of the electrode assembly 10 (that is, the Figure 3 vertical direction in

[0040] ); for the first arc section 112 and the second arc section 114 of the first electrode sheet 11, its thickness direction is not consistent with the thickness direction of the electrode assembly 10. As Figure 5 shown, in other embodiments, the first adhesive member 40 does not overlap with the second adhesive member 50 along the thickness direction of the first electrode sheet 11. Define the width of the electrode assembly 10 along the second direction Y as W 1 . The distance between the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 along the winding direction D of the electrode assembly 10 is W 2 , where 0 < W 2 ≤0.15W1 。

[0041] It can be understood that when mechanical abuse occurs (referring to the machine or device being affected by external mechanical forces such as collision, extrusion, and needle prick under the action of external mechanical forces, resulting in damage to its internal structure or abnormal function), the electrode assembly 10 slips relative to the housing 30. The head and tail of the electrode assembly 10 (i.e., Figure 1 the two ends along the first direction X) are easily squeezed to cause a short circuit. The arc segment at the corner of the electrode assembly 10 is a weak area and is also prone to being impacted and deformed to cause a short circuit.

[0042] In this application, a first bonding member 40 is provided on the outermost circle (the first electrode tab 11) of the electrode assembly 10, and the first bonding member 40 is at least bonded to the first arc segment 112. The first bonding member 40 is of the same length as the first electrode tab 11 or the edge along the first direction X extends beyond the edge of the first electrode tab 11 along the first direction X. By adjusting the relative position between the first bonding member 40 and the second bonding member 50, the first bonding member 40 can reinforce the weak area of the arc segment, fix the edge of the first electrode tab 11, and also has a certain reinforcing effect on the first electrode tab 11 (the outermost circle of the electrode assembly 10). Therefore, when mechanical abuse occurs, the first bonding member 40 can improve the impact resistance of the head, tail, and arc segment of the first electrode tab 11, and reduce the probability of the electrode assembly 10 slipping relative to the housing 30, thereby improving the drop resistance of the electrochemical device 100 and enhancing the safety of the electrochemical device 100. In addition, compared with the technical solution of increasing the thickness of the base materials (such as copper foil, aluminum foil, and separator), the technical solution of setting the first bonding member 40 in this application has almost negligible impact on the energy density of the electrochemical device 100 (the first bonding member 40 is relatively light in weight). Therefore, the electrochemical device 100 of this application has both a relatively high energy density and improved safety performance.

[0043] In some embodiments, along the first direction X, the edge of the first bonding member 40 does not extend beyond the edge of the separator 13. In the electrode assembly 10, the separator 13 has the largest size to better prevent the first electrode tab 11 and the second electrode tab 12 from directly contacting and causing a short circuit. That is, along the first direction X, the width of the separator 13 is greater than the width of the first electrode tab 11 and also greater than the width of the second electrode tab 12; along the second direction Y, the length of the separator 13 is greater than the length of the first electrode tab 11 and also greater than the length of the second electrode tab 12. The edge of the first bonding member 40 along the first direction X only needs to extend beyond the edge of the first electrode tab 11 to play its role in improving the drop resistance, without extending beyond the edge of the separator 13, so as to minimize the impact on the energy density of the electrochemical device 100.

[0044] In some embodiments, such as Figure 4As shown, along the first direction X, the first edge 41 of the first adhesive member 40 extends beyond the third edge 43 of the first pole piece 11, and the extending distance is L 1 ; the second edge 42 of the first adhesive member 40 also extends beyond the fourth edge 44 of the first pole piece 11, and the extending distance is L 2 . In this embodiment, L 1 = L 2 . In other embodiments, L 1 > L 2 , or, L 1 < L 2 . In some other embodiments, along the first direction X, the first edge 41 of the first adhesive member 40 is flush with the third edge 43 of the first pole piece 11 (L 1 = 0), and the second edge 42 of the first adhesive member 40 extends beyond the fourth edge 44 of the first pole piece 11 (L 2 > 0, that is, L 1 < L 2 ). In some other embodiments, along the first direction X, the first edge 41 of the first adhesive member 40 extends beyond the third edge 43 of the first pole piece 11 (L 1 > 0), and the second edge 42 of the first adhesive member 40 is flush with the fourth edge 44 of the first pole piece 11 (L 2 = 0, that is, L 1 > L 2 ).

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

[0046] In some embodiments, as shown in Figure 3 and Figure 4 , the first current collector 115 includes a first surface 1151 and a second surface 1152 which are 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 is disposed on the first surface 1151, and the second active material layer 1162 is disposed on the second surface 1152. Along the winding direction D, the first active material layer 1161 extends beyond the second active material layer 1162. The first adhesive member 40 is disposed in the area where the second active material layer 1162 is not provided on the second surface 1152, that is, the first adhesive member 40 is disposed in the empty foil area of the second surface 1152. In this embodiment, the first surface 1151 is the surface (inner surface) of the first pole piece 11 facing the center of the electrode assembly 10, and the second surface 1152 is the surface (outer surface) of the first pole piece 11 facing away from the center of the electrode assembly 10.

[0047] Further, the second adhesive member 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 bonds 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 bonds the end of the second active material layer 1162 along the winding direction D. At the junction position of the active material layer 116 and the first current collector 115, due to the possible unevenness or burrs of the active material layer 116, the separator 13 may be damaged, resulting in a 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 member 40 at least partially overlaps with the second adhesive member 50 along the thickness direction of the first electrode tab 11, indicating that the first adhesive member 40 overlaps with at least one of the first adhesive portion 51 and the second adhesive portion 52 along the thickness direction of the first electrode tab 11. The first adhesive member 40 does not overlap with the second adhesive member 50 along the thickness direction of the first electrode tab 11, indicating that the first adhesive member 40 does not overlap with either the first adhesive portion 51 or the second adhesive portion 52 along the thickness direction of the first electrode tab 11.

[0049] In some embodiments, such as Figure 3 shown, the electrode assembly 10 may include a straight region 101 and an arc region 102 connected in sequence along the winding direction D. The arc region 102 is a region where the side surface of the electrode assembly 10 is bent in an arc shape. The arc region 102 may correspond to one or more radii, and the straight region 101 is a straight section connecting the arc region 102. The first section 111 and the second section 113 of the first electrode tab 11 are located in the straight region 101, and the first arc section 112 and the second arc section 114 of the first electrode tab 11 are located in the arc region 102. As Figure 3 、 Figure 5 and Figure 6 shown, in some embodiments, the first adhesive portion 51 and the second adhesive portion 52 may extend from the straight region 101 to the arc region 102.

[0050] In some embodiments, such as Figure 3 shown, the first adhesive member 40 overlaps with the second adhesive member 50 along the thickness direction of the first electrode tab 11, and the overlapping dimension of the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 along the winding direction D is W 3 , 0 ≤ W 3 ≤ 0.15W 1 . When the overlapping dimension W 3 = 0, it means that the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 just meet, and at this time, it can also be regarded as a special case of overlapping. When W 3Greater than 0.15W 1 When it is greater than 0.15W, the improvement effect on the anti-drop performance is limited, and there is no need to increase the overlapping size at this time. That is, 0 ≤ W 3 ≤ 0.15W 1 , which can not only ensure the improvement effect on the anti-drop performance of the electrochemical device 100, but also reduce the impact on the energy density of the electrochemical device 100.

[0051] Furthermore, as Figure 3 shown, when the overlapping area is located in the flat area 101, W 3 is the straight-line distance of the overlapping area along the second direction Y. In some other embodiments, when the overlapping area is located in the flat area 101 and the arc area 102, W 3 is the sum of the straight-line distance of the overlapping area along the second direction Y and the perimeter of the arc segment of the overlapping area along the winding direction D.

[0052] When the first adhesive member 40 does not overlap with the second adhesive member 50 along the thickness direction of the first pole piece 11, and the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 are both located in the flat area 101, the spacing W 2 is the straight-line distance along the second direction Y between the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40. When the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 are both located in the arc area 102, the spacing W 2 is the perimeter of the arc segment formed between the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 along the winding direction D. When one of the winding start end of the second adhesive member 50 and the winding end of the first adhesive member 40 is located in the arc area 102 and the other is located in the flat area 101, the spacing W 2 is the sum of the straight-line distance and the arc segment perimeter.

[0053] In some embodiments, in addition to bonding the first section 111 and the first arc section 112, the first adhesive member 40 also bonds the second arc section 114. Thus, the first adhesive member 40 has a certain protective effect on the exposed surface of the outermost first current collector 115, and can further improve the anti-drop performance of the electrochemical device 100.

[0054] In some embodiments, as Figure 3 , Figure 5 and Figure 6 shown, the positive projection of the first adhesive member 40 along the thickness direction Z of the electrode assembly 10 overlaps at least partially with the positive projection of the third adhesive member 60 along the thickness direction Z of the electrode assembly 10. Thus, the first adhesive member 40 and the second adhesive member 60 can cooperate to enhance the integrity of the electrode assembly 10, thereby improving the anti-impact performance of the electrode assembly 10.

[0055] In some embodiments, the first electrode tab 11 is a cathode electrode tab, and the second electrode tab 12 is an anode electrode tab. The first current collector 115 may be, but is not limited to, aluminum foil. The active material layer 116 may include substances such as cathode active materials, conductive agents, and binders. The cathode active material may be, but is not limited to, lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material (NCM), lithium manganese oxide (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ), lithium iron phosphate (LiFePO 4 ), etc.

[0056] In some embodiments, as shown in Figure 3 , Figure 5 and Figure 6 , the second electrode tab 12 includes a second current collector 121 and active material layers 122 provided on opposite surfaces of the second current collector 121. The second current collector 121 may be, but is not limited to, copper foil. The active material layer 122 may include anode active materials, conductive agents, and binders, etc. The anode active material may be, but is not limited to, one or a combination of one or more of graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium. Among them, the graphite may be selected from one or a combination of one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material may be selected from one or a combination of one or more of elemental silicon, silicon oxides, silicon-carbon composites, and silicon alloys; the tin-based material may be selected from one or a combination of one or more of elemental tin, tin oxides, and tin alloys. Along 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 circle of the electrode assembly 10 is the first electrode tab 11, and the end of the first electrode tab 11 along the winding direction is the end of the first current collector 115. That is, the electrode assembly 10 uses the first current collector 115 (such as aluminum foil) of the first electrode tab 11 as the finishing section, and the first current collector 115 can increase the hardness of the electrode assembly 10 and play a role in protecting the electrode assembly 10.

[0057] Furthermore, the electrochemical device 100 may further include a fourth adhesive member 70. The fourth adhesive member 70 is adhered to the end of the first current collector 115 along the winding direction D to fix the ending first current collector 115, thereby reducing the probability of the electrode assembly 10 unrolling. One end of the fourth adhesive member 70 away from the first current collector 115 is adhered by the third adhesive member 60, enhancing the fixing effect on the ending section of the first current collector 115. The fourth adhesive member 70 is a single-sided adhesive, reducing the friction between the outer surface of the outermost first electrode tab 11 of the electrode assembly 10 and the housing 30 and lowering the risk of damage to the outermost first electrode tab 11. The third adhesive member 60 is a double-sided adhesive, with one side adhered to the first current collector 115 and the fourth adhesive member 70 and the other side adhered to the housing 30, enabling relative fixation between the electrode assembly 10 and the housing 30. In some other embodiments, the fourth adhesive member 70 may be omitted, and the third adhesive member 60 may be adhered to the end of the first current collector 115 along the winding direction D to fix the ending first current collector 115.

[0058] In some embodiments, as Figure 6 shown, the first adhesive member 40 may extend to cover the third adhesive member 60 and then extend to adhere to the end of the first current collector 115 along the winding direction D to further enhance the anti-drop performance.

[0059] In some embodiments, as Figure 2 shown, the electrochemical device 100 may further include a fifth adhesive member 80. The fifth adhesive member 80 may be disposed at the end of the electrode assembly 10 away from the electrode tab 20. The fifth adhesive member 80 can wind from one surface of the electrode assembly 10 to the bottom of the electrode assembly 10 (the part where the electrode tab 20 protrudes is the head of the electrode assembly 10, and the opposite of the head is the tail), and then wind to the other surface. Therefore, the fifth adhesive member 80 is also referred to as winding glue. The fifth adhesive member 80 can inhibit the endothermic expansion of the electrode assembly 10, ensure the stability of the winding structure of the electrode assembly 10, and reduce the probability of the electrode assembly 10 unrolling. The fifth adhesive member 80 may be a single-sided adhesive.

[0060] In some embodiments, the separator 13 may include a porous substrate, which may be, but is not limited to, polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, aramid, etc. In some embodiments, the separator 13 further includes a coating provided on the porous substrate, and the coating includes at least one of a binder and inorganic particles. The binder may be, but is not limited to, a copolymer of vinylidene fluoride - hexafluoropropylene, a copolymer of vinylidene fluoride - trichloroethylene, polyacrylate, polyacrylic acid, polyacrylate salt, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, etc., and the inorganic particles may be, but is not limited to, silica, alumina, 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 housing 30 is a packaging bag obtained by encapsulating with a packaging film (such as an aluminum - plastic film), that is, 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 may be, but is not limited to, one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate, ethyl butyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ - butyrolactone, vinylene carbonate, propylene sulfite. The lithium salt may be, but is not limited to, one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium perchlorate, lithium trifluoromethanesulfonate.

[0063] Please refer to Figure 7 , a 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 laptop 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 (cathode electrode)

[0067] The cathode active material lithium cobaltate (LiCoO 2) The conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 0.75, and the mixture is stirred evenly. The slurry is evenly coated on the aluminum foil (the first current collector) so that the weight of the cathode active material on the electrode sheet is 180 g / m 2 . It is dried at 90 °C to complete the single-sided coating of the electrode sheet, and the other side is coated in the same way. After the coating is completed, the cathode active material layer of the electrode sheet is cold-pressed to a compaction density of 4.0 g / cm 3 . Subsequently, auxiliary processes such as tab welding and attaching the first adhesive, the second adhesive, the third adhesive, and the fourth adhesive are carried out, and the entire preparation process of the first electrode sheet is completed.

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

[0069] The anode active material graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR) are mixed in a weight ratio of 96:1.5:2.5, and deionized water (H 2 O) is added as a solvent to prepare a slurry with a solid content of 0.7, and the mixture is stirred evenly. The slurry is evenly coated on the copper foil (the second current collector), and the weight of the anode active material on the electrode sheet is 95 g / m 2 . It is dried at 110 °C to complete the single-sided coating of the electrode sheet, and the other side is coated in the same way. After the coating is completed, the anode active material layer of the electrode sheet is cold-pressed to a compaction density of 1.7 g / cm 3 . Subsequently, auxiliary processes such as tab welding and attaching the adhesive (adhesive tape) are carried out, and the entire preparation process of the second electrode sheet is completed.

[0070] (3) Preparation of the electrolyte

[0071] In a dry argon atmosphere, first, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC = 30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF 6 ) is added to the organic solvent and dissolved and mixed evenly to obtain an electrolyte with a lithium salt concentration of 1.15 M.

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

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

[0074] Place the electrode assembly in a housing (aluminum plastic film), inject electrolyte and encapsulate to obtain an electrochemical device.

[0075] In this embodiment, the length of the electrode assembly along the first direction X is 90.0 mm, the width W along the second direction Y 1 is 34.0 mm, and the thickness is 5.0 mm. The length of the first electrode sheet along the first direction X is 82.7 mm. The length of the first bonding member along the first direction X is 86.7 mm, and its first edge (upper edge) along the first direction X extends beyond the third edge (upper edge) of the first electrode sheet, L 1 = 2 mm, and its second edge (lower edge) along the first direction X extends beyond the fourth edge (lower edge) of the first electrode sheet, L 2 = 2 mm. The thickness of the first bonding member is 16 μm. The first bonding portion of the first bonding member and the second bonding member does not overlap (as Figure 5 shown), and the distance W between the winding end of the first bonding member and the winding start end of the first bonding portion of the second bonding member 2 is 5.1 mm (i.e., 0.15W 1 ).

[0076] Example 2

[0077] The difference between Example 2 and Example 1 is that the distance W between the winding end of the first bonding member and the winding start end of the first bonding portion of the second bonding member 2 is 3.0 mm. The rest are the same as in Example 1 and will not be elaborated here.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that the distance W between the winding end of the first bonding member and the winding start end of the first bonding portion of the second bonding member 2 is 1.0 mm. The rest are the same as in Example 1 and will not be elaborated here

[0080] Example 4

[0081] The difference between Example 4 and Example 1 is that the first bonding portion of the first bonding member and the second bonding member exactly overlaps, W 3 is 0 mm. The rest are the same as in Example 1 and will not be elaborated here.

[0082] Example 5

[0083] The difference between Example 5 and Example 1 is that the first bonding portion of the first bonding member and the second bonding member overlaps (as Figure 3 shown), and the overlapping dimension W 3 is 1.0 mm. The rest are the same as in Example 1 and will not be elaborated here.

[0084] Example 6

[0085] Example 6 is different from Example 5 in that: the overlapping dimension W 3 is 2.0 mm. The rest are the same as in Example 5 and will not be elaborated here.

[0086] Example 7

[0087] Example 7 is different from Example 5 in that: the overlapping dimension W 3 is 5.1 mm. The rest are the same as in Example 5 and will not be elaborated here.

[0088] Example 8

[0089] Example 8 is different from Example 6 in that: L 1 = 0.0 mm, L 2 = 0 mm. The rest are the same as in Example 6 and will not be elaborated here.

[0090] Example 9

[0091] Example 9 is different from Example 6 in that: L 2 = 0 mm. The rest are the same as in Example 6 and will not be elaborated here.

[0092] Example 10

[0093] Example 10 is different from Example 6 in that: L 1 = 0 mm. The rest are the same as in Example 6 and will not be elaborated here.

[0094] Example 11

[0095] Example 11 is different from Example 6 in that: L 1 = 1.0 mm, L 2 = 1.0 mm. The rest are the same as in Example 6 and will not be elaborated here.

[0096] Example 12

[0097] Example 12 is different from Example 6 in that: a fifth bonding member (i.e., winding glue, as Figure 2 shown) is provided at the bottom of the electrode assembly. The rest are the same as in Example 6 and will not be elaborated here.

[0098] Comparative Example 1

[0099] Comparative Example 1 is different from Example 1 in that: the first bonding member is not provided. The rest are the same as in Example 1 and will not be elaborated here.

[0100] Comparative Example 2

[0101] The difference between Comparative Example 2 and Example 1 is that the first edge of the first bonding member is indented 1.0 mm inward compared to the third edge of the first pole piece (i.e., L 1 = -1.0 mm), and the second edge is indented 1.0 mm inward compared to the fourth edge of the first pole piece (i.e., L 2 = -1.0 mm); the distance W 2 between the winding start end of the first bonding portion of the second bonding member and the winding end of the first bonding member is 6.0 mm, exceeding 0.15W 1 (5.10 mm). The rest are the same as in Example 1 and will not be elaborated here.

[0102] Comparative Example 3

[0103] The difference between Comparative Example 3 and Example 1 is that L 1 = 0 mm, L 2 = 0 mm, and the distance W 2 between the winding start end of the first bonding portion of the second bonding member and the winding end of the first bonding member is 6.0 mm, exceeding 0.15W 1 (5.10 mm). The rest are the same as in Example 1 and will not be elaborated here.

[0104] Five electrochemical devices were selected from each of Examples 1 to 12 and Comparative Examples 1 to 3 for numbering. The voltage before the drop test was measured, then the drop test was carried out, and then the voltage after the drop was measured. Finally, the average voltage drop of the five electrochemical devices in each example and comparative example was calculated and recorded as the voltage drop of that example or comparative example. If the electrochemical device after the test does not catch fire, explode, smoke, or leak liquid, and the voltage drop before and after the test is less than 30 mV, it is considered to pass the drop test.

[0105] The specific steps of the drop test are as follows. Each electrochemical device was placed in a drop fixture and fixed on one side with double-sided tape. In a test environment of 25 ± 5 °C, using a marble drop floor, the electrochemical device was dropped once from a drop height of 1.5 m along each of its six surfaces and once at each of its four corners, for a total of five rounds of tests. The voltage of the electrochemical device was measured 24 h after the test.

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

[0107] Table 1

[0108]

[0109]

[0110] As can be seen from the data in Table 1, the voltage drops of the electrochemical devices in Examples 1 to 12 of the present application are all controlled within 30 mV, and after the drop test, there is no fire, explosion, smoke, or liquid leakage, and all pass the drop test. Among the electrochemical devices of Comparative Examples 1 to 3, the voltage drops of the electrochemical devices far exceed 30 mV, and the electrochemical devices in Comparative Examples 1 to 3 do not pass the drop test. It shows that the first adhesive of the present application can improve the drop resistance of the electrochemical device.

[0111] By comparing Examples 1 to 3 and Examples 4 to 7, it can be seen that the voltage drops in Examples 4 to 7 are all lower than those in Examples 1 to 3, indicating that the effect of the overlap of the first adhesive and the second adhesive is better than that of the non - overlap of the first adhesive and the second adhesive. From Examples 1 to 3, it can be seen that the distance W between the first adhesive and the second adhesive 2 The smaller it is, the more conducive it is to the decrease of the voltage drop. From Examples 4 to 7, it can be seen that within a certain range, increasing the overlapping size W 3 is helpful to reduce the voltage drop, thereby improving the safety performance of the electrochemical device.

[0112] From Examples 8 to 11, it can be seen that when the edge of the first adhesive exceeds the edge of the first electrode tab (L 1 and L 2 at least one of them is greater than 0), its voltage drop is slightly lower than that when the first adhesive is flush with the edge of the first electrode tab (L 1 and L 2 are both 0). Further, in Examples 8 to 11, when the two edges of the first adhesive evenly exceed the two edges of the first electrode tab, its voltage drop is the smallest (Example 11); when only one edge of the first adhesive exceeds the edge of the first electrode tab, the voltage drop is the second (Examples 9 and 10), and the effect of the first edge exceeding the third edge is basically the same as that of the second edge exceeding the fourth edge; when the two edges of the first adhesive are flush with the two edges of the first electrode tab, its voltage drop is the largest (Example 8).

[0113] By comparing Examples 6, Example 8, and Example 11, it can be seen that within a certain range, increasing the size of L 1 and L 2 is helpful to reduce the voltage drop. From Examples 6 and Example 12, it can be seen that for Example 12 with winding glue, its voltage drop is slightly higher than that of Example 6 without winding glue. This is because when the edge of the first adhesive exceeds the edge of the first electrode tab, the first adhesive may interfere with the bottom winding glue, thereby affecting the voltage drop and drop performance.

[0114] By comparing Comparative Example 1 with Comparative Example 2 and Comparative Example 3 respectively, it can be seen that although the distance W 2 (6.0 mm) between the first adhesive and the second adhesive in Comparative Example 2 exceeds 0.15W 1(in the range of 5.10 mm) and the edge of the first bonding member is recessed, and the distance W between the first bonding member and the second bonding member in Comparative Example 3 2 (6.0 mm) exceeds 0.15W 1 (in the range of 5.10 mm). However, the pressure drops of Comparative Example 2 and Comparative Example 3 are still lower than that of Comparative Example 1, indicating that as long as the first bonding member is provided, the anti-drop performance can be improved to a certain extent. To achieve the optimal effect, the structure and position of the first bonding member need to be optimized.

[0115] In the electrochemical device 100 and the electronic device 200 according to the embodiments of the present application, by providing the first bonding member 40 at the outermost circle (the first pole piece 11) of the electrode assembly 10, and making the first bonding member 40 bond to at least the first arc segment 112, and the first bonding member 40 is as long as the first pole piece 11 or the edge along the first direction X extends beyond the edge of the first pole piece 11, and adjusting the relative position between the first bonding member 40 and the second bonding member 50, so that the first bonding member 40 strengthens the weak area of the arc segment, and can also fix the edge of the first pole piece 11 and has a certain strengthening effect on the first pole piece 11. Therefore, when mechanical abuse occurs, the first bonding member 40 can improve the anti-impact performance of the head and tail of the first pole piece 11 and the arc segment, and can reduce the probability of slippage between the electrode assembly 10 and the housing 30, thereby improving the anti-drop performance of the electrochemical device 100 and enhancing the safety of the electrochemical device 100. In addition, the weight of the first bonding member 40 is relatively light, and its influence on the energy density of the electrochemical device 100 can be almost ignored. Therefore, the electrochemical device 100 of the present application has both a relatively high energy density and improved safety performance.

[0116] The above description is some specific embodiments of the present application, but in the actual application process, it cannot be limited to these embodiments only. For those of ordinary skill in the art, other deformations and changes made according to the technical concept of the present application should fall within the protection scope of the present application.

Claims

1. An electrochemical device, characterized in that: The electrochemical device comprises an electrode assembly, a pole ear and a shell for accommodating the electrode assembly; the pole ear is electrically connected to the electrode assembly and extends from the shell, and the direction in which the pole ear extends from the shell is defined as a first direction; the electrode assembly comprises a first pole piece, a second pole piece and a separator disposed between the first pole piece and the second pole piece, and the electrode assembly is a winding structure; The electrochemical device further includes a first adhesive member, the outermost circle of the electrode assembly is the first pole piece, the outermost circle of the first pole piece includes a first segment, a first arc segment, a second segment, and a second arc segment connected in sequence, and the first adhesive member at least bonds the first arc segment and extends to the first segment; Along the first direction, the first adhesive member is equal in length to the first pole piece, or an edge of the first adhesive member exceeds an edge of the first pole piece; The electrochemical device further comprises a second adhesive and a third adhesive, the first electrode sheet comprises a first current collector and an active material layer disposed on a surface of the first current collector, the second adhesive is bonded to an end of the active material layer along a winding direction, the third adhesive is disposed on an outer surface of the second section, and the third adhesive is bonded to the housing; The first adhesive at least partially overlaps with the second adhesive along the thickness direction of the first pole piece; or, The first adhesive member does not overlap with the second adhesive member along the thickness direction of the first pole piece; Along the second direction, the width of the electrode assembly is W1; the spacing between the winding starting 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 according to claim 1, characterized in that Along the first direction, the edge of the first adhesive component does not exceed the edge of the isolation film.

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

4. The electrochemical device according to claim 2, characterized in that Along the first direction, the first adhesive has a first edge and a second edge arranged opposite to each other, the first pole piece has a third edge and a fourth edge arranged opposite to each other, the first edge exceeds the third edge by a distance L1, and the second edge exceeds the fourth edge by a distance L2, wherein L1>L2 or L1<L2.

5. The electrochemical device according to claim 1, characterized in that The first adhesive overlaps with the second adhesive along the thickness direction of the first pole piece, and an overlapping dimension between a winding start end of the second adhesive and a winding end end of the first adhesive along the winding direction is W3, 0≤W3≤0.15W1.

6. The electrochemical device according to claim 1, wherein: 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 exceeds the second active material layer; The first adhesive member is disposed on a region of the second surface where the second active material layer is not disposed.

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

8. The electrochemical device according to claim 7, characterized in that Along the winding direction, the electrode assembly includes an arc area and a straight area connected in sequence, the first segment and the second segment are located in the straight area, the first arc segment and the second arc segment are located in the arc area, and at least one of the first bonding portion and the second bonding portion is located in the arc area.

9. The electrochemical device according to claim 1, wherein: The second pole piece includes a second current collector, and along the winding direction, an end of the second current collector does not exceed an end of the first current collector.

10. The electrochemical device according to claim 1, wherein An orthographic projection of the first adhesive along the thickness direction of the electrode assembly at least partially overlaps with an orthographic projection of the third adhesive along the thickness direction of the electrode assembly.

11. The electrochemical device according to claim 1, wherein The first pole piece is a cathode pole piece, and the second pole piece is an anode pole piece.

12. An electronic device, characterized in that: Comprising the electrochemical device according to any one of claims 1 to 11.

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