Electrochemical device and electronic device

Abstract

An electrochemical device includes an electrode assembly. The electrode assembly is of a winding structure and comprises a first pole piece, a second pole piece and an isolating membrane arranged between the first pole piece and the second pole piece. The first pole piece comprises a first current collector and a first active material layer, and the first current collector comprises a first empty foil area. The second pole piece comprises a second current collector and a second active material layer, and the second current collector comprises a second empty foil area. The first empty foil region comprises a first region; the first region is positioned on the outermost layer of the first pole piece; the second empty foil region comprises a second region; the second region is positioned on the outermost layer of the second pole piece. The electrochemical device further comprises a bonding piece, the bonding piece comprises a bonding layer and a metal layer which are arranged in a stacked mode, the bonding layer comprises a conductive material, and the bonding piece bonds at least one of the first area and the second area through the bonding layer. The invention further provides an electronic device. The safety and reliability of the electrochemical device can be improved.

Description

Electrochemical devices and electronic devices Technical Field

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

[0002] Electrochemical devices (such as batteries) are widely used in electronic products such as mobile devices, power tools, and electric vehicles. To improve the pass rate of safety tests such as needle puncture and heavy object impact, extended positive and negative electrode foil areas can be installed at the end of the electrode assembly to form a vest structure on the outer ring of the electrode assembly after winding. If a sharp external conductor pierces the electrochemical device, a short circuit can quickly occur between the extended positive and negative electrode foil areas, causing the electrochemical device to discharge.

[0003] However, the safety test pass rate of existing electrochemical devices is still low.

[0004] Summary of the Invention

[0005] In order to solve the above shortcomings, it is necessary to provide an electrochemical device.

[0006] In addition, it is also necessary to provide an electronic device having the above electrochemical device.

[0007] In a first aspect, the present application provides an electrochemical device comprising an electrode assembly. The electrode assembly is a wound structure comprising a first electrode sheet, a second electrode sheet, and an isolation membrane disposed between the first electrode sheet and the second electrode sheet. The first electrode sheet comprises a first current collector and a first active material layer disposed on the surface of the first current collector, the first current collector comprising a first empty foil area where the first active material layer is not disposed. The second electrode sheet comprises a second current collector and a second active material layer disposed on the surface of the second current collector, the second current collector comprising a second empty foil area where the second active material layer is not disposed. The first empty foil area comprises a first region, the first region being located at the outermost layer of the first electrode sheet. The second empty foil area comprises a second region, the second region being located at the outermost layer of the second electrode sheet. The electrochemical device further comprises an adhesive member, the adhesive member comprising an adhesive layer and a metal layer stacked together. The adhesive layer comprises a conductive material. The adhesive member bonds at least one of the first area and the second area via the adhesive layer.

[0008] In the present application, when the electrochemical device is subjected to mechanical abuse (such as needle puncture or heavy object impact), the first region and the second region can be connected and short-circuited through the adhesive, and the short-circuit current in the electrode assembly can be shunted to discharge the electrochemical device, thereby reducing the risk of fire or explosion of the electrochemical device. At the same time, the adhesive can improve the mechanical strength of the first region and / or the second region, reducing the risk of high-temperature melting at the short-circuit point, so that the electrochemical device can continue to short-circuit through the short-circuit point when subjected to the above-mentioned mechanical abuse, thereby improving the safety and reliability of the electrochemical device. Moreover, the adhesive is only provided on at least one of the first region and the second region, which also reduces the impact on the energy density of the electrochemical device.

[0009] In some possible implementations, along the winding direction of the electrode assembly, the first region includes a first section, a first bending section, a second section, and a second bending section connected in sequence. An adhesive is provided on the surface of the first section and the second section. Therefore, when the electrochemical device is punctured from one side of the first section or the second section (especially when the puncture depth is less than the thickness of the electrochemical device) or hit by a heavy object, the first region and the second region can be short-circuited and the risk of melting at the short-circuit point can be reduced. In particular, when the first region is aluminum foil in some embodiments, the adhesive can reduce the risk of the aluminum foil first melting at high temperature at the short-circuit point during puncture. Moreover, when the foreign matter completely passes through the electrochemical device, the adhesive increases the number of short-circuit points in the electrode assembly where a continuous short circuit may occur, which is beneficial for shunting the short-circuit current in the electrode assembly faster and improving the safety and reliability of the electrochemical device.

[0010] In some possible implementations, the adhesive is further disposed on the surface of at least one of the first and second bend sections. Therefore, when the electrochemical device is punctured or struck by a heavy object from one side of the first or second bend section, the first and second regions can be short-circuited, and the risk of fusing at the short-circuit point is reduced, allowing the electrochemical device to maintain a short circuit through the short-circuit point, further improving safety and reliability.

[0011] In some possible implementations, along the winding direction of the electrode assembly, the second region includes a third bending section, a third section, a fourth bending section and a fourth section connected in sequence. The adhesive is provided on the surface of the third section and the fourth section. Therefore, when the electrochemical device is punctured from one side of the third section or the fourth section (especially when the puncture depth is less than the thickness of the electrochemical device) or hit by a heavy object, the first region and the second region can be short-circuited and the risk of melting of the short-circuit point can be reduced. In particular, when the second region is copper foil in some embodiments, the adhesive is bonded to the surface of the copper foil so that the mechanical strength of the vest structure is more significantly improved. Therefore, when a heavy object hits, the copper foil can maintain a larger area in contact with the aluminum foil and conduct, thereby shunting the short-circuit current in the electrode assembly. Moreover, when the foreign matter completely passes through the electrochemical device, the adhesive increases the number of short-circuit points in the electrode assembly where a continuous short circuit may occur, which is beneficial for shunting the short-circuit current in the electrode assembly faster and improving the safety and reliability of the electrochemical device.

[0012] In some possible implementations, the adhesive is further disposed on the surface of at least one of the third and fourth bend segments. Therefore, when the electrochemical device is punctured or struck by a heavy object from one side of the third or fourth bend segment, the first and second regions can be short-circuited, and the risk of melting at the short-circuit point is reduced.

[0013] In some possible implementations, the adhesive disposed in the first region and the adhesive disposed in the second region are located on different sides of the winding center of the electrode assembly along the winding direction of the electrode assembly. In this case, if the electrochemical device is punctured or struck by a heavy object from different sides of the winding center, the first and second regions can be short-circuited, and the risk of melting at the short-circuit point is reduced, allowing the electrochemical device to continuously short-circuit at the short-circuit point, thereby improving safety and reliability.

[0014] In some possible implementations, the adhesive disposed in the first region and the adhesive disposed in the second region are located on the same side of the winding center of the electrode assembly along the winding direction of the electrode assembly. In this case, if a foreign object passes through or a heavy object strikes the first and second regions where the adhesive is disposed, the adhesive can simultaneously enhance the mechanical strength of the first and second regions at the same short-circuit point, further reducing the risk of melting at the short-circuit point and improving the safety and reliability of the electrochemical device.

[0015] In some possible implementations, the electrode assembly further includes a first tab and a second tab. The first tab is electrically connected to the first current collector, and the second tab is electrically connected to the second current collector. The adhesive member is provided with a first recess and a second recess. In the thickness direction of the electrode assembly, the projection of the first recess in the first region overlaps the projection of the first tab in the first region, and the projection of the second recess in the first region overlaps the projection of the second tab in the first region. Consequently, the overall thickness of the electrode assembly corresponding to the first and second tabs is reduced, compensating for the increase in the overall thickness of the electrochemical device caused by the provision of the adhesive member, thereby facilitating improved energy density.

[0016] In some possible implementations, the adhesive layer includes at least one of conductive silver glue or conductive silicone glue, which provides the adhesive layer with high conductivity and adhesion. In some possible implementations, the metal layer includes at least one of copper, aluminum, titanium, or nickel, which provides the metal layer with high conductivity.

[0017] In some possible implementations, the thickness of the adhesive layer is 4 to 10 microns. This improves the bonding reliability of the adhesive layer while reducing the impact of an excessively thick adhesive layer on the energy density of the electrochemical device. In some possible implementations, the thickness of the metal layer is 4 to 20 microns. This improves the mechanical strength of the first region and / or the second region while reducing the impact of an excessively thick metal layer on the energy density of the electrochemical device.

[0018] In some possible implementations, the first region is located at the outermost ring of the electrode assembly, and the second region is located at the second outermost ring of the electrode assembly. By providing the first region as the final section, the first current collector can increase the hardness of the electrode assembly. Furthermore, when the second current collector is copper foil in some embodiments, the risk of electrolyte corrosion during the final section of the second current collector is reduced.

[0019] A second aspect of the present application further provides an electronic device, which includes the above electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] FIG1 is a front view of an electrochemical device provided in one embodiment of the present application.

[0022] FIG. 2 is a top view of an electrode assembly of the electrochemical device shown in FIG. 1 in some embodiments.

[0023] FIG3 is a schematic diagram of an expanded view of the first electrode piece of the electrode assembly shown in FIG2 .

[0024] FIG. 4 is a schematic diagram of an expanded view of the second electrode piece of the electrode assembly shown in FIG. 2 .

[0025] FIG5 is a cross-sectional view of the adhesive member of the electrochemical device shown in FIG2.

[0026] FIG6 is a back view of the first pole piece shown in FIG3 .

[0027] FIG. 7 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0028] FIG. 8 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0029] FIG. 9 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0030] FIG. 10 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0031] FIG. 11 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0032] FIG. 12 is a top view of the electrode assembly of the electrochemical device shown in FIG. 1 in some other embodiments.

[0033] FIG13 is a schematic structural diagram of an electronic device provided in one embodiment of the present application.

[0034] Description of main component symbols

[0035] Electronic device 1

[0036] Housing 10

[0037] First housing 11

[0038] Second housing 12

[0039] Electrode assembly 20

[0040] First pole piece 21

[0041] Second pole piece 22

[0042] Isolation film 23

[0043] First tab 30

[0044] Second tab 40

[0045] Adhesive 50

[0046] Adhesive layer 50a

[0047] Metal layer 50b

[0048] 1st recessed part 50c

[0049] 2nd recessed part 50d

[0050] First adhesive member 51

[0051] Second adhesive 52

[0052] The third adhesive member 53

[0053] Fourth adhesive member 54

[0054] Fifth adhesive member 55

[0055] Sixth adhesive member 56

[0056] Electrochemical device 100

[0057] First current collector 210

[0058] First active material layer 211

[0059] First empty foil area 212

[0060] Second current collector 220

[0061] Second active material layer 221

[0062] Second empty foil area 222

[0063] Edge 500

[0064] First Area 2120

[0065] First paragraph 2121

[0066] First bending section 2122

[0067] Second paragraph 2123

[0068] Second bending section 2124

[0069] Third Area 2125

[0070] Fourth Area 2126

[0071] Second area 2220

[0072] Section 3 2221

[0073] The third bending section 2222

[0074] Section 4 2223

[0075] Fourth bending section 2224

[0076] Winding direction D

[0077] Winding center O

[0078] First direction X

[0079] Second direction Y

[0080] The third direction Z

[0081] Thickness T1, T2 DETAILED DESCRIPTION

[0082] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0083] Below, embodiments of the present application will be described in detail. However, the present application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments illustrated herein. Rather, these exemplary embodiments are provided to make the present application thorough and detailed for those skilled in the art.

[0084] In addition, for the sake of brevity and clarity, the size or thickness of various components or layers may be exaggerated in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, element A can be directly connected to element B, or there may be an intermediate element C and element A and element B can be indirectly connected to each other.

[0085] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0086] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0087] The spatially related terms used herein, such as "on", etc., can be used herein for convenient description to describe the relationship between an element or feature and another element (multiple elements) or feature (multiple features) as illustrated in the figure. It should be understood that, in addition to the directions described in the figure, spatially related terms are intended to include different directions of equipment or devices in use or operation. For example, if the equipment in the figure is flipped, the elements described as "above" or "on" other elements or features will be oriented "below" or "below" other elements or features. Therefore, the exemplary term "on" can include the direction above and below. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts in this article, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below can be referred to as the second element, component, region, layer or part without departing from the teachings of the exemplary embodiments.

[0088] Referring to Figures 1 and 2 , one embodiment of the present application provides an electrochemical device 100 comprising a housing 10 and an electrode assembly 20 disposed within the housing 10. In some embodiments, the electrochemical device 100 is a soft-pack battery. The housing 10 may be a packaging bag encapsulated with an encapsulating film, i.e., the electrochemical device 100 is a soft-pack battery. In other embodiments, the electrochemical device 100 may also be a steel-cased battery or an aluminum-cased battery, which is not a limitation of this application.

[0089] The electrode assembly 20 is a wound structure and includes a first electrode sheet 21, a second electrode sheet 22, and a separator 23 disposed between the first electrode sheet 21 and the second electrode sheet 22. The separator 23 prevents direct contact between the first electrode sheet 21 and the second electrode sheet 22, thereby reducing the possibility of a short circuit between the first electrode sheet 21 and the second electrode sheet 22. The electrochemical device 100 also includes a first electrode tab 30 and a second electrode tab 40. The first electrode tab 30 is electrically connected to the first electrode sheet 21, and the second electrode tab 40 is electrically connected to the second electrode sheet 22. The first electrode tab 30 and the second electrode tab 40 extend from one end of the housing 10 to connect to an external device (not shown). A three-dimensional coordinate system is established based on mutually perpendicular first, second, and third directions (X, Y, and Z). In this application, the first direction (X) is the direction from the first electrode tab 30 to the second electrode tab 40; the second direction (Y) is the direction in which the first electrode tab 30 and the second electrode tab 40 extend from the electrode assembly 20, or the direction of the winding center (O) of the electrode assembly 20; and the third direction (Z) is the thickness direction of the electrode assembly 20. The first electrode sheet 21, the separator 23, and the second electrode sheet 22 are stacked in sequence and wound around a winding center O to form the electrode assembly 20. For example, the stack 2 can be wound counterclockwise (winding direction D) around the winding center O to form the electrode assembly 20. In some embodiments, the first electrode sheet 21 can be a positive electrode sheet, and the second electrode sheet 22 can be a negative electrode sheet. In other embodiments, the first electrode sheet 21 can be a negative electrode sheet, and the second electrode sheet 22 can be a positive electrode sheet.

[0090] As shown in Figures 2 and 3, the first electrode 21 includes a first current collector 210 and a first active material layer 211 respectively provided on two opposite surfaces of the first current collector 210. The first current collector 210 has the function of collecting current. For example, the first current collector 210 may include aluminum or nickel. In some embodiments, the first current collector 210 includes aluminum. The first active material layer 211 includes an active material, such as at least one of lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium-rich manganese-based material, or lithium nickel cobalt aluminum oxide.

[0091] The first current collector 210 includes a first hollow foil region 212, with the first active material layer 211 not provided on either surface. The first hollow foil region 212 includes a first region 2120, which is located at the outermost layer of the first electrode sheet 21. Furthermore, in some embodiments, the first region 2120 is located at the outermost periphery of the electrode assembly 20. By providing the first region 2120 as a finishing section, the first current collector 210 can, on the one hand, increase the hardness of the electrode assembly 20, protecting the electrode assembly 20 and reducing the risk of failure or damage to the electrochemical device 100 when dropped. On the other hand, it also reduces the risk of electrolyte corrosion of the second current collector 220 (e.g., copper foil) during the finishing of the second current collector 220. In some embodiments, along the winding direction D of the electrode assembly 20, the first region 2120 includes a first segment 2121, a first bent segment 2122, a second segment 2123, and a second bent segment 2124, which are sequentially connected. The first segment 2121 and the second segment 2123 can both be straight segments. At this time, the third direction Z is also the direction from the first section 2121 to the second section 2123. In other embodiments, the first section 2121 and the second section 2123 may also be bent sections.

[0092] As shown in Figures 2 and 4, the second electrode 22 includes a second current collector 220 and a second active material layer 221 provided on the surface of the second current collector 220. The second current collector 220 has the function of collecting current. For example, the second current collector 220 may include copper, nickel, or a carbon-based conductor. In some embodiments, the second current collector 220 includes copper. The second active material layer 221 includes an active material, which may be selected from at least one of graphite materials, alloy materials, lithium metal, and alloys thereof. The graphite material may be selected from at least one of artificial graphite and natural graphite; the alloy material may be selected from at least one of silicon, silicon oxide, tin, and titanium sulfide.

[0093] The second current collector 220 includes a second hollow foil area 222, and the second active material layer 221 is not provided on either surface of the second hollow foil area 222. The second hollow foil area 222 includes a second region 2220, which is located at the outermost layer of the second electrode sheet 22. In some embodiments, along the winding direction D of the electrode assembly 20, the second region 2220 includes a third bent segment 2222, a third segment 2221, a fourth bent segment 2224, and a fourth segment 2223, which are connected in sequence. The third segment 2221 and the fourth segment 2223 can both be straight segments. In other embodiments, the third segment 2221 and the fourth segment 2223 can also be bent segments.

[0094] As shown in Figure 2, in the third direction Z, the first segment 2121, the third segment 2221, the fourth segment 2223, and the second segment 2123 are arranged in sequence and opposite to each other. When viewed from the second direction Y, the first segment 2121 and the third segment 2221 are located on the same side of the winding center O, while the second segment 2123 and the fourth segment 2223 are located on the other side of the winding center O. In the first direction X, the second curved segment 2124, the third curved segment 2222, the fourth curved segment 2224, and the first curved segment 2122 are arranged in sequence and opposite to each other. When viewed from the second direction Y, the second curved segment 2124 and the third curved segment 2222 are located on the same side of the winding center O, while the first curved segment 2122 and the fourth curved segment 2224 are located on the other side of the winding center O.

[0095] Among them, the "outermost layer" in this application means that when the first pole piece 21 is wound along the winding direction D, the first region 2120 is located at the outermost side or outermost circle of the first pole piece 21 after winding; when the first pole piece 21 is wound along the winding direction D, the second region 2220 is located at the outermost side or outermost circle of the second pole piece 22 after winding.

[0096] In some embodiments, the first region 2120 is located at the outermost circle of the electrode assembly 20 , and the second region 2220 is located at the second outer circle of the electrode assembly 20 .

[0097] At least a portion of the second region 2220 is disposed opposite the first region 2120 via the isolation film 23. In some embodiments, the third segment 2221 is disposed opposite the first segment 2121 via the isolation film 23, the fourth bent segment 2224 is disposed opposite the first bent segment 2122 via the isolation film 23, and the fourth segment 2223 is disposed opposite the second segment 2123 via the isolation film 23. In this way, the first region 2120, the second region 2220, and the separator 23 disposed between the first region 2120 and the second region 2220 can collectively form the vest (MJ) structure of the electrode assembly 20. The vest structure is the part most likely to cause contact short circuits when the electrochemical device 100 is mechanically abused (for example, during a needle puncture, a foreign object pierces the first region 2120, the separator 23, and the second region 2220, causing a contact short circuit between the first region 2120 and the second region 2220; or when a heavy object hits, the separator 23 shrinks or ruptures, causing a contact short circuit between the first region 2120 and the second region 2220). In some embodiments, the first empty foil area 212 may further include a third area 2125 and a fourth area 2126. In the winding direction D, the third area 2125, the first region 2120, and the fourth area 2126 are connected in sequence. Therefore, the first empty foil area 212 forms more than one circle outside the first electrode sheet 21. In some embodiments, the second hollow foil region 222 includes only the second area 2220. Therefore, the second hollow foil region 222 forms exactly one circle outside the second electrode piece 22. In this application, "one circle" means starting from a certain point on the winding structure as the starting end, and completing one circle along the winding direction D to reach another point as the ending end, with the ending end and the starting end being on a straight line along the third direction Z.

[0098] As shown in Figures 2 and 3, the electrochemical device 100 further includes an adhesive member 50. Referring also to Figure 5, the adhesive member 50 includes a laminated adhesive layer 50a and a metal layer 50b. The adhesive layer 50a comprises a conductive material, and the adhesive member 50 is bonded to at least one of the first region 2120 and the second region 2220 via the adhesive layer 50a. Because the adhesive member 50 is entirely made of a conductive material, when the electrochemical device 100 is subjected to mechanical abuse (such as needle puncture or impact by a heavy object), the first region 2120 and the second region 2220 can contact and conduct through the adhesive member 50, quickly short-circuiting. This shunts the short-circuit current within the electrode assembly 20, allowing the electrochemical device 100 to discharge, thereby reducing the risk of fire or explosion. At the same time, the adhesive 50 can improve the mechanical strength of the first region 2120 and / or the second region 2220, reducing the risk of high-temperature melting at the short-circuit point, so that the electrochemical device 100 can continue to short-circuit through the short-circuit point when subjected to the above-mentioned mechanical abuse, thereby improving safety and reliability.

[0099] Furthermore, in the prior art, to reduce the risk of melting at the short-circuit point between the first and second empty foil regions during mechanical abuse, such as needle puncture or heavy object impact, the current collector thickness can be increased, or a primer layer can be added to the surface of the first current collector to increase contact resistance. However, the adhesive member 50 of the present application is only provided on at least one of the first region 2120 and the second region 2220. This not only reduces the risk of high-temperature melting at the short-circuit point during mechanical abuse, but also minimizes the impact on the energy density of the electrochemical device 100.

[0100] As shown in FIG2 , in some embodiments, the adhesive 50 is disposed on the first region 2120. Furthermore, in some embodiments, as viewed from the second direction Y, along the winding direction D, the adhesives 50 disposed in the first region 2120 are located on different sides of the winding center O. For example, the adhesives 50 disposed in the first region 2120 are located on different sides of the winding center O in the third direction Z. In this case, if the electrochemical device 100 is needle-punctured from different sides of the winding center O (especially when the needle-puncture depth is less than the thickness of the electrochemical device 100, such as when the needle-puncture depth is 50% of the thickness of the electrochemical device 100, i.e., shallow puncture) or struck by a heavy object, the first region 2120 and the second region 2220 can be short-circuited, and the risk of melting at the short-circuit point is reduced. Moreover, when the foreign object completely penetrates the electrochemical device 20 (such as the needle penetration depth is 100% of the thickness of the electrochemical device 100, that is, full puncture), the adhesive 50 located on different sides of the winding center O increases the number of short-circuit points in the electrode assembly 20 where a continuous short circuit may occur, which is beneficial to shunting the short-circuit current in the electrode assembly 20 faster, further reducing the risk of fire or explosion of the electrochemical device 100, and improving the safety and reliability of the electrochemical device 100.

[0101] In some embodiments, the adhesive layer 50a includes at least one of conductive silver paste or conductive silicone, thereby providing the adhesive layer 50a with high conductivity and adhesion. In some embodiments, the metal layer 50b includes at least one of copper, aluminum, titanium, or nickel, thereby providing the metal layer 50b with high conductivity.

[0102] As shown in FIG5 , in some embodiments, the thickness T1 of the adhesive layer 50a is between 4 and 10 microns. This improves the reliability of the adhesive layer 50a adhering to the first region 2120 and / or the second region 2220 while reducing the impact of an excessively thick adhesive layer 50a on the energy density of the electrochemical device 100. In some embodiments, the thickness T2 of the metal layer 50b is between 4 and 20 microns. This improves the mechanical strength of the first region 2120 and / or the second region 2220 while reducing the impact of an excessively thick metal layer 50b on the energy density of the electrochemical device 100.

[0103] Referring to FIG. 6 , in some embodiments, the adhesive member 50 is provided with a first recess 50 c and a second recess 50 d. In the third direction Z, the projection of the first recess 50 c in the first region 2120 overlaps the projection of the first electrode tab 30 in the first region 2120, and the projection of the second recess 50 d in the first region 2120 overlaps the projection of the second electrode tab 40 in the first region 2120. The provision of the first recess 50 c and the second recess 50 d reduces the overall thickness of the electrode assembly 20 along the third direction Z at locations corresponding to the first and second electrode tabs 30 and 40, thereby compensating for the increase in overall thickness of the electrochemical device 100 at locations corresponding to the first and second electrode tabs 30 and 40 caused by the provision of the adhesive member 50, thereby facilitating improved energy density. The first recess 50 c and the second recess 50 d both extend through one edge 500 of the adhesive member 50 at the winding center O. In the thickness direction of the adhesive member 50 (i.e., the stacking direction of the adhesive layer 50a and the metal layer 50b), the depths of the first recess 50c and the second recess 50d can be set according to the thickness of the first electrode tab 30 and the second electrode tab 40. For example, each of the first recess 50c and the second recess 50d can be provided on the adhesive layer 50a, or on the metal layer 50b, or on both the adhesive layer 50a and the metal layer 50b.

[0104] The present application will be described in detail below with reference to specific embodiments. Unless there is any conflict, the following embodiments and features therein may be combined with each other.

[0105] Example 1

[0106] As shown in Figure 2, the adhesive member 50 includes a first adhesive member 51 and a second adhesive member 52. The first adhesive member 51 and the second adhesive member 52 are spaced apart in the winding direction D. In this embodiment, the first adhesive member 51 and the second adhesive member 52 are bonded to the surfaces of the first segment 2121 and the second segment 2123, respectively. Therefore, when viewed from the second direction Y, the first adhesive member 51 and the second adhesive member 52 are located on different sides of the winding center O. Furthermore, the first adhesive member 51 is disposed on the surface of the first segment 2121 facing the winding center O, while the second adhesive member 52 is disposed on the surface of the second segment 2123 facing the winding center O.

[0107] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Because aluminum foil has a low melting point, the adhesive 50 adheres to the surface of the aluminum foil, reducing the risk of the aluminum foil fusing at the short-circuit point during needle penetration. Therefore, the electrochemical device 100 exhibits greater safety and reliability during needle penetration.

[0108] Example 2

[0109] As shown in Figure 7, the adhesive member 50 is disposed on the second region 2220. In this embodiment, the adhesive member 50 includes a third adhesive member 53 and a fourth adhesive member 54. The third adhesive member 53 and the fourth adhesive member 54 are spaced apart in the winding direction D. The third adhesive member 53 and the fourth adhesive member 54 are adhered to the surfaces of the third segment 2221 and the fourth segment 2223, respectively. Therefore, when viewed from the second direction Y, the third adhesive member 53 and the fourth adhesive member 54 are located on different sides of the winding center O. Furthermore, the third adhesive member 53 is disposed on the surface of the third segment 2221 facing the winding center O, and the fourth adhesive member 54 is disposed on the surface of the fourth segment 2223 facing the winding center O.

[0110] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Compared to Example 1, due to the higher hardness and mechanical strength of the copper foil itself, the adhesive 50 adheres to the surface of the copper foil, significantly improving the mechanical strength of the vest structure. Therefore, when a heavy object strikes, the copper foil can maintain a larger area of ​​contact and conduction with the aluminum foil, shunting the short-circuit current within the electrode assembly 20. As a result, the electrochemical device 100 has higher safety and reliability when struck by a heavy object.

[0111] Example 3

[0112] As shown in Figure 8, the adhesive 50 is disposed on both the first region 2120 and the second region 2220. In this embodiment, the adhesive 50 includes a first adhesive 51 and a fourth adhesive 54. In the winding direction D, the first adhesive 51 and the fourth adhesive 54 are spaced apart. The first adhesive 51 is bonded to the surface of the first segment 2121, and the fourth adhesive 54 is bonded to the surface of the fourth segment 2223. Therefore, when viewed from the second direction Y, the first adhesive 51 and the fourth adhesive 54 are located on different sides of the winding center O. Furthermore, the first adhesive 51 is disposed on the surface of the first segment 2121 facing the winding center O, and the fourth adhesive 54 is disposed on the surface of the fourth segment 2223 facing the winding center O.

[0113] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Compared to Examples 1 and 2, since the adhesive 50 is provided on the copper foil and the aluminum foil, respectively, the electrochemical device 100 has higher safety and reliability when subjected to needle puncture and heavy object impact.

[0114] Example 4

[0115] As shown in Figure 9, the adhesive 50 is disposed on both the first region 2120 and the second region 2220. In this embodiment, the adhesive 50 includes a second adhesive 52 and a third adhesive 53. In the winding direction D, the second adhesive 52 and the third adhesive 53 are spaced apart. The second adhesive 52 is bonded to the surface of the second segment 2123, and the third adhesive 53 is bonded to the surface of the third segment 2221. Therefore, when viewed from the second direction Y, the second adhesive 52 and the third adhesive 53 are located on different sides of the winding center O. Furthermore, the second adhesive 52 is disposed on the surface of the second segment 2123 facing the winding center O, and the third adhesive 53 is disposed on the surface of the third segment 2221 facing the winding center O.

[0116] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Compared to Examples 1 and 2, since the adhesive 50 is provided on the copper foil and the aluminum foil, respectively, the electrochemical device 100 can have higher safety and reliability when subjected to needle puncture and heavy object impact.

[0117] Example 5

[0118] As shown in Figure 10, the adhesive 50 is disposed on both the first region 2120 and the second region 2220. In this embodiment, the adhesive 50 includes a second adhesive 52 and a fourth adhesive 54. In the winding direction D, the second adhesive 52 and the fourth adhesive 54 are spaced apart. The second adhesive 52 is bonded to the surface of the second segment 2123. The fourth adhesive 54 is bonded to the surface of the fourth segment 2223. Therefore, when viewed from the second direction Y, the second adhesive 52 and the fourth adhesive 54 are located on the same side of the winding center. Furthermore, the second adhesive 52 is disposed on the surface of the second segment 2123 facing the winding center O, while the fourth adhesive 54 is disposed on the surface of the fourth segment 2223 facing the winding center O.

[0119] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Compared to Examples 3 and 4, when the electrochemical device 100 is punctured by a needle or struck by a heavy object, the adhesive 50 simultaneously improves the mechanical strength of both the copper and aluminum foils at the same short-circuit point, thereby further reducing the risk of melting at the short-circuit point and improving the safety and reliability of the electrochemical device 100.

[0120] Example 6

[0121] As shown in Figure 11, in this embodiment, the adhesive member 50 includes a first adhesive member 51, a second adhesive member 52, a third adhesive member 53, and a fourth adhesive member 54. In the winding direction D, the first adhesive member 51, the second adhesive member 52, the third adhesive member 53, and the fourth adhesive member 54 are spaced apart. The first adhesive member 51 and the second adhesive member 52 are bonded to the surfaces of the first segment 2121 and the second segment 2123, respectively. The third adhesive member 53 and the fourth adhesive member 54 are bonded to the surfaces of the third segment 2221 and the fourth segment 2223, respectively. Therefore, when viewed from the second direction Y, the first adhesive member 51 and the third adhesive member 53 are located on one side of the winding center O, while the second adhesive member 52 and the fourth adhesive member 54 are located on the other side of the winding center O.

[0122] In this embodiment, the first current collector 210 is aluminum foil, and the second current collector 220 is copper foil. Compared to Example 5, when a foreign object completely passes through the electrode assembly 20, the adhesive members 50 located on different sides of the winding center O increase the number of short-circuit points within the electrode assembly 20 where a sustained short circuit can occur. This helps to more quickly shunt the short-circuit current within the electrode assembly 20, thereby improving the safety and reliability of the electrochemical device 100.

[0123] Example 7

[0124] The difference from Example 6 is that, as shown in FIG12 , the first adhesive member 51 and the second adhesive member 52 can be connected in the winding direction D. In this case, the adhesive member 50 may further include a fifth adhesive member 55. The fifth adhesive member 55 is provided on the surface of at least one of the first bending section 2122 and the second bending section 2124 to connect the first adhesive member 51 and the second adhesive member 52.

[0125] Furthermore, in the winding direction D, the third adhesive member 53 and the fourth adhesive member 54 may also be connected. In this case, the adhesive member 50 may further include a sixth adhesive member 56. The sixth adhesive member 56 is disposed on the surface of at least one of the third bent section 2222 and the fourth bent section 2224, and is used to connect the third adhesive member 53 and the fourth adhesive member 54. In this case, when the electrochemical device 100 is punctured or struck by a heavy object along the first direction X, the first region 2120 and the second region 2220 can be short-circuited, and the risk of melting at the short-circuit point is reduced.

[0126] The electrochemical device 100 of the present application includes all devices capable of generating an electrochemical reaction. Specifically, the electrochemical device 100 includes all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors (e.g., supercapacitors). Alternatively, the electrochemical device 100 may be a secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, and a sodium ion battery.

[0127] Referring to FIG13 , one embodiment of the present application further provides an electronic device 1 comprising the electrochemical device 100. The electronic device 1 of the present application may be, but is not limited to, a laptop computer, a pen-type computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery, a lithium-ion capacitor, and the like.

[0128] The performance of the electrochemical device 100 provided in the present application is described below in combination with the comparative example and the above-mentioned embodiments 1-7.

[0129] Comparative Example

[0130] Similar to the first embodiment, the difference is that the electrochemical device 100 is not provided with the adhesive member 50 .

[0131] Then, 10 electrochemical devices 100 from each group of examples and comparative examples were taken and subjected to a needle penetration test and an impact test, respectively. The test results are recorded in Table 1.

[0132] The steps of the needle penetration test include: 1) fully charging the electrochemical device 100 at 25±3°C (constant current charging the electrochemical device 100 at 0.5C to 4.4V, and then constant voltage charging the electrochemical device 100 at 4.4V until the current reaches 0.05C); 2) using a carbon steel nail with a diameter of 4mm to needle-penetrate the front surface of the electrochemical device 100 (i.e., the outer surface of the second section 2123) at room temperature (e.g., 25°C) at a needle penetration speed of 100mm / s, and the needle penetration depth is based on the steel nail penetrating 50% of the thickness of the electrochemical device 100; 3) observing the electrochemical device 100 for fire or explosion.

[0133] The impact test steps include: 1) fully charging the electrochemical device 100 at 25±3°C (constant current charging of 0.5C to 4.4V, then constant voltage charging of 4.4V to a current of 0.05C); 2) placing the electrochemical device 100 on a test bench and vertically placing a 15.8mm diameter round rod at the center of the front of the electrochemical device 100; 3) using a 9.1±0.1kg hammer, drop it vertically from a height of 610±25mm to impact the intersection of the round rod and the front of the electrochemical device 100; 4) observing whether the battery catches fire or explodes.

[0134] Table 1

[0135] Impact test pass rate Needle penetration test pass rate Comparative Example 2 / 10 3 / 10 Example 1 6 / 10 10 / 10 Example 2 10 / 10 6 / 10 Example 3 10 / 10 6 / 10 Example 4 8 / 10 10 / 10 Example 5 10 / 10 10 / 10 Example 6 10 / 10 10 / 10 Example 7 10 / 10 10 / 10

[0136] Note: The test pass rate X / 10 means that among the 10 samples tested, the number of samples that passed the test is X.

[0137] As can be seen from the test results in Table 1, compared to the comparative example, since the adhesive 50 is provided on at least one of the first area 2120 and the second area 2220 in Examples 1-7, the test pass rate in the needle puncture and heavy object impact tests is higher, which can better improve the safety performance of the electrochemical device. Among them, the test found that compared to Example 1 and Example 4, since Examples 2-3 and 5-7 all have the adhesive 50 provided on the second area 2220 (especially at the fourth section 2223) located on the front of the electrochemical device 100, the test pass rate in the heavy object impact test is relatively higher. Compared to Example 2-3, since Examples 1 and 4-7 all have the adhesive 50 provided on the first area 2120 (especially at the second section 2123) located on the front of the electrochemical device 100, the test pass rate in the needle puncture test is relatively higher.

[0138] The above disclosure is only a preferred embodiment of the present application and certainly cannot be used to limit the present application. Therefore, equivalent changes made based on the present application are still within the scope covered by the present application.

Claims

1. An electrochemical device, comprising an electrode assembly, wherein the electrode assembly is a wound structure, including a first electrode sheet, a second electrode sheet, and a separator disposed between the first electrode sheet and the second electrode sheet, the first electrode sheet including a first current collector and a first active material layer disposed on a surface of the first current collector, the first current collector including a first hollow foil region not provided with the first active material layer, the second electrode sheet including a second current collector and a second active material layer disposed on a surface of the second current collector, the second current collector including a second hollow foil region not provided with the second active material layer; The first empty foil area includes a first region, the first region is located at the outermost layer of the first pole piece, and the second empty foil area includes a second region, the second region is located at the outermost layer of the second pole piece; in, The electrochemical device further includes an adhesive member including an adhesive layer and a metal layer stacked together, the adhesive layer including a conductive material, and the adhesive member bonds at least one of the first region and the second region via the adhesive layer.

2. The electrochemical device according to claim 1, wherein Along the winding direction of the electrode assembly, the first region includes a first segment, a first bending segment, a second segment, and a second bending segment connected in sequence, and the adhesive is arranged on surfaces of the first segment and the second segment.

3. The electrochemical device according to claim 2, wherein The adhesive is further provided on a surface of at least one of the first bending section and the second bending section.

4. The electrochemical device according to claim 1 or 2, wherein Along the winding direction of the electrode assembly, the second region includes a third bending segment, a third segment, a fourth bending segment and a fourth segment connected in sequence, and the adhesive is arranged on surfaces of the third segment and the fourth segment.

5. The electrochemical device according to claim 4, wherein The adhesive is further provided on a surface of at least one of the third bending segment and the fourth bending segment.

6. The electrochemical device according to claim 1, wherein Along the winding direction of the electrode assembly, the adhesive member disposed in the first region and the adhesive member disposed in the second region are respectively located on different sides of a winding center of the electrode assembly.

7. The electrochemical device according to claim 1, wherein Along the winding direction of the electrode assembly, the adhesive member disposed in the first region and the adhesive member disposed in the second region are respectively located on the same side of a winding center of the electrode assembly.

8. The electrochemical device according to claim 1, wherein The electrode assembly further includes a first electrode tab and a second electrode tab, wherein the first electrode tab is electrically connected to the first current collector, and the second electrode tab is electrically connected to the second current collector; A first recess and a second recess are provided on the adhesive. In the thickness direction of the electrode assembly, the projection of the first recess in the first region covers the projection of the first electrode tab in the first region, and the projection of the second recess in the first region covers the projection of the second electrode tab in the first region.

9. The electrochemical device according to claim 1, wherein The bonding layer includes at least one of conductive silver glue or conductive silicone glue, and / or the metal layer includes at least one of copper, aluminum, titanium or nickel.

10. The electrochemical device according to claim 1, wherein The thickness of the adhesive layer is 4 micrometers to 10 micrometers, and / or the thickness of the metal layer is 4 micrometers to 20 micrometers.

11. The electrochemical device according to claim 1, wherein The first region is located at the outermost circle of the electrode assembly, and the second region is located at the second outer circle of the electrode assembly.

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

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