Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery includes an electrode assembly, a first tab, and a second tab. The electrode assembly comprises a first pole piece and a second pole piece which are opposite in electric polarity, and the first pole piece and the second pole piece are arranged in a winding mode. The first tab is connected with the first pole piece; the second tab is connected with the second pole piece. In the thickness direction of the electrode assembly, the first tab and the second tab are located on adjacent layers of the electrode assembly respectively, a first empty foil groove is formed in the side, facing the second pole piece, of the first pole piece, the first tab is arranged in the first empty foil groove, a second empty foil groove is formed in the side, facing the first pole piece, of the second pole piece, and the second tab is arranged in the second empty foil groove; the first tab is insulated from the second tab; the projection of the first empty foil groove and the projection of the second empty foil groove are at least partially overlapped in the thickness direction of the electrode assembly. The first empty foil groove and the second empty foil groove are at least partially overlapped, so that the removal of active material layers of other pole piece layers is reduced, and the energy density of the secondary battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a secondary battery and an electric device. BACKGROUND

[0002] With the continuous updating and development of secondary battery technology, the application field of secondary batteries is also expanding. The existing positive and negative tabs of the secondary battery usually extend from different positions of the cell shell, increasing the occupied space and having a certain influence on the energy density of the secondary battery. SUMMARY

[0003] Therefore, it is necessary to provide a secondary battery and an electric device, which can save space and improve energy density.

[0004] Embodiments of the present application provide a secondary battery, which comprises an electrode assembly, a first tab and a second tab. The electrode assembly comprises first and second electrode sheets with opposite polarities, and the first and second electrode sheets are wound together. The first tab is connected to the first electrode sheet. The second tab is connected to the second electrode sheet. In the thickness direction of the electrode assembly, the first and second tabs are located on adjacent layers of the electrode assembly, the first electrode sheet is provided with a first empty foil groove on the side facing the second electrode sheet, the first tab is arranged in the first empty foil groove, the second electrode sheet is provided with a second empty foil groove on the side facing the first electrode sheet, and the second tab is arranged in the second empty foil groove. The first tab is insulated from the second tab. In the thickness direction of the electrode assembly, the projection of the first empty foil groove and the projection of the second empty foil groove at least partially overlap. When the area of the positive active material layer is greater than that of the negative active material layer, the lithium extraction capacity of the positive active material layer is greater than the lithium insertion capacity of the negative active material layer, and the negative active material layer cannot accommodate the lithium ions extracted from the positive active material layer, which easily causes lithium precipitation risk. If the second empty foil groove is arranged on the side of the second electrode sheet away from the adjacent first electrode sheet, in order to reduce the risk of lithium precipitation, part of the positive active material layer of another first electrode sheet adjacent to the second electrode sheet needs to be provided with an additional empty foil groove to remove part of the positive active material, resulting in a decrease in the energy density of the secondary battery. In the present application, the first and second empty foil grooves are arranged on the sides of the first and second electrode sheets facing each other, and in the thickness direction of the electrode assembly, the projection of the first empty foil groove and the projection of the second empty foil groove at least partially overlap, so that no additional empty foil groove is needed, the number of empty foil grooves is reduced, the removal of the active material layer of other electrode sheet layers is reduced, more active material layers can be accommodated on the electrode sheet, and the energy density of the secondary battery is improved.

[0005] In one or more optional embodiments above, the first electrode sheet is a positive electrode sheet, and the second electrode sheet is a negative electrode sheet.

[0006] In one or more optional embodiments above, a projection of the second empty foil groove is located within a projection of the first empty foil groove along a thickness direction of the electrode assembly. The risk of lithium plating caused by the negative active material layer being unable to accommodate lithium ions stripped from the positive active material layer is reduced.

[0007] In one or more optional embodiments above, a projection of the second tab is spaced apart from a projection of an edge of the first empty foil groove along a thickness direction of the electrode assembly. The thickness of the electrode assembly is increased by the second tab overlapping the first active material layer in the thickness direction of the electrode assembly, which affects the energy density of the secondary battery.

[0008] In one or more optional embodiments above, a projection of the second tab is spaced apart from an edge of the first empty foil groove by a distance h along a winding direction of the electrode assembly, 1mm≤h≤5mm. By h≥1mm, the second tab does not overlap the first active material layer in the thickness direction of the electrode assembly, which reduces the impact on the energy density of the secondary battery. By h≤5mm, the distance is reduced based on the second tab not overlapping the first active material layer, which maximizes the retention of the positive active material and is conducive to improving the energy density of the secondary battery.

[0009] In one or more optional embodiments above, a projection of the second tab does not exceed a projection of the first tab along a thickness direction of the electrode assembly, and the first tab is insulatedly connected to the second tab and forms a first electrical connector. By the second tab overlapping the first tab or the second tab not exceeding the first tab along the thickness direction of the electrode assembly, the first tab and the second tab form a first electrical connector. By one electrical connector, the compatibility of the secondary battery with the battery compartment is higher compared to the first tab and the second tab extending from different positions, and it is also conducive to reducing the space occupied by the tab extension and improving the energy density.

[0010] In one or more optional embodiments above, the first tab includes a first segment extending out of the electrode assembly, and the second tab includes a second segment extending out of the electrode assembly. The secondary battery includes a first insulating member between the first segment and the second segment, the first insulating member connecting the first segment and the second segment, and the first segment and the second segment forming a first electrical connector.

[0011] In one or more optional embodiments above, the first tab is welded to the first empty foil groove and forms a first weld mark, the secondary battery includes a first protective member covering the first weld mark, and the first protective member is connected to the first insulating member; and / or, the second tab is welded to the second empty foil groove and forms a second weld mark, the secondary battery includes a second protective member covering the second weld mark, and the second protective member is connected to the first insulating member. The first insulating member and the second protective member completely cover the second tab, further reducing the risk of short circuit.

[0012] In one or more optional embodiments above, the secondary battery includes a first metal piece and a second metal piece. The first metal piece is electrically connected to the portion of the first tab extending out of the electrode assembly, and the second metal piece is electrically connected to the portion of the second tab extending out of the electrode assembly. The projection of the first metal piece and the projection of the second metal piece overlap in the thickness direction of the electrode assembly, and the first metal piece is insulated from the second metal piece. The first metal piece and the second metal piece are overlapped and insulated, which facilitates the connection of the external electrical equipment. Compared with the first tab and the second tab extending out of the shell from different positions, the secondary battery has higher compatibility with the battery compartment.

[0013] In one or more optional embodiments above, the secondary battery includes a second insulating piece arranged between the first metal piece and the second metal piece, and the second insulating piece connects the first metal piece and the second metal piece and forms a second electrical connecting piece. The electrode assembly is arranged in the shell, and the second electrical connecting piece extends out of the shell. The second electrical connecting piece has an increased area sealed with the shell by the addition of the first metal piece and the second metal piece, thereby improving the sealing effect. The first metal piece and the second metal piece are external standard pieces, and the first metal piece, the second metal piece, and the second insulating piece can be pre-assembled into an integral whole, which facilitates the complete overlap of the first metal piece and the second metal piece and makes the portion of the second electrical connecting piece extending out of the shell more orderly, thereby facilitating the connection of the external electrical equipment.

[0014] In one or more optional embodiments above, the shell is provided with a recess, and the first electrical connecting piece or the second electrical connecting piece extends out of the shell from the recess. The position of the first electrical connecting piece or the second electrical connecting piece can be adjusted according to the structure of the shell, which improves the compatibility with the battery compartment and reduces the space occupied by the tab extending portion, thereby facilitating the improvement of the energy density.

[0015] The present application provides a kind of electrical equipment, including the secondary battery in any one embodiment described above. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The structure schematic diagram of the secondary battery in some embodiments is shown.

[0017] Figure 2 The cross-sectional schematic diagram of the secondary battery in some embodiments is shown.

[0018] Figure 3 The structure schematic diagram of part of the secondary battery in some embodiments is shown. Figure 2 The enlarged schematic diagram of A in Fig.

[0019] Figure 4 The structure schematic diagram of part of the secondary battery in some embodiments is shown.

[0020] Figure 5 The structure schematic diagram of part of the secondary battery in some embodiments is shown.

[0021] Figure 6 A structural diagram of the first and second tabs in some embodiments is shown.

[0022] Figure 7 A structural diagram of the secondary battery in other embodiments is shown.

[0023] Figure 8 A structural diagram of the secondary battery in still other embodiments is shown.

[0024] Figure 9 A simple diagram of the electrical device in some embodiments is shown.

[0025] Explanation of main element symbols: Secondary battery 100 Electrode assembly 10 First electrode tab 11 First empty foil groove 11a First edge 130 Second edge 140 Third insulating adhesive 150 Fourth insulating adhesive 160 First current collector 111 First active material layer 112 Second electrode tab 12 Second empty foil groove 12a Second current collector 121 Second active material layer 122 Separator 13 First tab 20 First section 21 Second tab 30 Second section 31 Third edge 310 Fourth edge 320 Housing 40 Recess 41 First insulating member 50 First insulating adhesive 51 Second insulating adhesive 52 First metal member 60 Second metal member 70 Second insulating member 80 First electrical connection member 101 First protective member 102 Second protective member 103 Second electrical connection member 104 Electrical device 200 First direction X Second direction Y The following specific embodiments will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0027] When a component is referred to as being “disposed on” another component, it can be directly disposed on the other component or there may be a component intervening therebetween. When a component is referred to as being “connected to” another component, it can be directly connected to the other component or there may be a component intervening therebetween.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] It can be understood that the term "perpendicular" is used to describe the ideal state between two components. In actual production or use, there may be a state between the two components that is approximately perpendicular or equal. For example, combined with numerical descriptions, perpendicular can refer to the angle between two straight lines being in the range of 90°±10°, perpendicular can also refer to the dihedral angle between two planes being in the range of 90°±10°, and perpendicular can also refer to the angle between a straight line and a plane being in the range of 90°±10°. The two components described as "perpendicular" may not be absolute straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if the overall extension direction is a straight line or a plane.

[0030] Unless otherwise defined, the term "plurality" herein, when used to describe the number of components, specifically means that the components are two or more.

[0031] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features of the embodiments may be combined with each other.

[0032] See also Figures 1 to 4 An embodiment of the present application provides a secondary battery 100 including an electrode assembly 10 . The electrode assembly 10 includes a first electrode sheet 11 and a second electrode sheet 12 with opposite polarities. The first electrode sheet 11 and the second electrode sheet 12 are wound together.

[0033] In some embodiments, the first tab 11 includes a first current collector 111 and a first active material layer 112 disposed on at least part of the first current collector 111. The second tab 12 includes a second current collector 121 and a second active material layer 122 disposed on at least part of the second current collector 121.

[0034] In some embodiments, the first tab 11 can be a positive electrode tab, and the second tab 12 can be a negative electrode tab. Correspondingly, the first current collector 111 is a positive electrode current collector, the first active material layer 112 includes a first active material, and the first active material is a positive electrode active material; the second current collector 121 is a negative electrode current collector, the second active material layer 122 includes a second active material, and the second active material is a negative electrode active material. The positive electrode current collector can be an aluminum foil or a nickel foil, and the negative electrode current collector can be at least one of a copper foil, a nickel foil, or a carbon-based current collector.

[0035] In some embodiments, the electrode assembly 10 includes a separator 13 disposed between the first tab 11 and the second tab 12 to reduce the risk of short circuiting between the first tab 11 and the second tab 12.

[0036] In some embodiments, the separator 13 includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.

[0037] The secondary battery 100 includes a first tab 20 connected to the first tab 11 and a second tab 30 connected to the second tab 12. The first tab 20 and the second tab 30 are located in adjacent layers of the electrode assembly 10, respectively.

[0038] For ease of description, the thickness direction of the electrode assembly 10 is defined as the first direction X. Along the first direction X, the side of the first tab 11 facing the second tab 12 is provided with a first empty foil groove 11a, and the first tab 20 is disposed in the first empty foil groove 11a. The side of the second tab 12 facing the first tab 11 is provided with a second empty foil groove 12a, and the second tab 30 is disposed in the second empty foil groove 12a. The first tab 20 and the second tab 30 are insulated, and the second empty foil groove 12a and the second empty foil groove 12b are disposed face to face, excluding the separator. The first empty foil groove 11a refers to a groove position on the first current collector 111 where the first active material layer 112 is not disposed, and the second empty foil groove 12a refers to a groove position on the second current collector 121 where the second active material layer 122 is not disposed.

[0039] When the area of the positive active material layer is greater than that of the negative active material layer, the positive active material layer can have a greater capacity for deintercalating lithium than the negative active material layer for intercalating lithium, and the negative active material layer cannot accommodate lithium ions deintercalated from the positive active material layer, which can easily cause lithium precipitation risk. If the second empty foil groove 12a is arranged on the side of the second tab 12 away from the adjacent first tab 11, in order to reduce the risk of lithium precipitation, part of the positive active material layer of the other first tab 11 adjacent to the second tab 12 needs to be removed, resulting in a decrease in the energy density of the secondary battery 100. The present application sets the first empty foil groove 11a and the second empty foil groove 12a on the side of the first tab 11 and the second tab 12 facing each other, i.e., the first empty foil groove 11a and the second empty foil groove 12a are arranged face to face and partially overlap, which reduces the removal of the active material layer of other tab layers, increases the capacity of the active material layer, and is beneficial to improve the energy density of the secondary battery 100. The number of empty foil grooves is reduced, i.e., the space occupied by the empty foil grooves is reduced, which is beneficial to improve the energy density.

[0040] In some embodiments, the secondary battery 100 includes a housing 40, and the electrode assembly 10 is arranged in the housing 40. The first electrical connection 101 extends out of the housing 40, facilitating connection to an external electrical device. Optionally, the housing 40 includes an aluminum plastic film.

[0041] In some embodiments, along the first direction X, the projection of the second empty foil groove 12a is located within the projection of the first empty foil groove 11a, reducing the risk of lithium precipitation caused by the negative active material layer being unable to accommodate lithium ions deintercalated from the positive active material layer.

[0042] In some embodiments, along the first direction X, the projection of the second tab 30 is separated from the projection of the edge of the first empty foil groove 11a, reducing the possibility of the second tab 30 overlapping the first active material layer 111 in the first direction X and increasing the thickness of the electrode assembly 10, which affects the energy density of the secondary battery 100.

[0043] In some embodiments, along the winding direction of the electrode assembly 10, the distance between the projection of the second tab 30 and the edge of the first empty foil groove 11a is h, and 1mm≤h≤5mm. By h≥1mm, the second tab 30 does not overlap the first active material layer 111 in the first direction X, reducing the impact on the energy density of the secondary battery 100. By h≤5mm, on the basis that the second tab 30 does not overlap the first active material layer 111, the distance is reduced, as much as possible to retain the positive active material, which is beneficial to improve the energy density of the secondary battery 100.

[0044] Along the first direction X, the projection of the second tab 30 does not exceed the projection of the first tab 20, the first tab 20 is insulatedly connected to the second tab 30, and forms a first electrical connection 101.

[0045] The second tab 30 is insulatedly connected with the first tab 20 by the first empty foil slot 11a. Along the first direction X, the second tab 30 overlaps the first tab 20 or the second tab 30 does not exceed the first tab 20 (as shown in Figure 6 The first tab 20 and the second tab 30 are combined to form a first electrical connection 101. The electrical energy is transmitted through the first electrical connection 101. Compared with the first tab 20 and the second tab 30 extending from different positions, the compatibility of the secondary battery to the battery compartment is higher, and it is beneficial to reduce the space occupied by the tab extension and improve the energy density.

[0046] In some embodiments, along the second direction Y, the first empty foil slot 11a includes a first edge 130 and a second edge 140, and the first tab 20 is located between the first edge 130 and the second edge 140. Along the second direction Y, the second tab 30 includes a third edge 310 and a fourth edge 320, and the interval between the fourth edge 320 and the second edge 140 along the second direction Y is h, and the interval between the first edge 130 and the third edge 310 along the second direction Y is h.

[0047] Please refer to Figure 4 In some embodiments, the first empty foil slot 11a exposes the surface of the first current collector 111 towards the adjacent second tab 12, and the first tab 20 is welded to the first current collector 111 in the first empty foil slot 11a and forms a first welding mark (not shown in the figure).

[0048] In some embodiments, the secondary battery 100 includes a first protective member 102, which is bonded to the first active material layer 112 and the first tab 20 and covers the first welding mark, thereby reducing the risk of the first welding mark piercing the isolation film 13 and causing short circuit. Optionally, the first protective member 102 includes an insulating adhesive tape.

[0049] In some embodiments, the second empty foil slot 12a exposes the surface of the second current collector 121 towards the adjacent first tab 11, and the second tab 30 is welded to the second current collector 121 in the second empty foil slot 12a and forms a second welding mark (not shown in the figure).

[0050] In some embodiments, the secondary battery 100 includes a second protective member 103, which is bonded to the second active material layer 122 and the second tab 30 and covers the second welding mark, thereby reducing the risk of the second welding mark piercing the isolation film 13 and causing short circuit. Optionally, the second protective member 103 includes an insulating adhesive tape.

[0051] Please refer to Figure 4 In some embodiments, the secondary battery 100 includes a first insulating member 50, which is located between the first tab 20 and the second tab 30 to insulate the first tab 20 and the second tab 30.

[0052] In some embodiments, the first insulating member 50 is connected to the first protective member 102, the first insulating member 50 is connected to the second protective member 103, the first insulating member 50 and the first protective member 102 completely cover the first pole ear 20, and the first insulating member 50 and the second protective member 103 completely cover the second pole ear 30, further reducing the risk of short circuit.

[0053] In some embodiments, the first electrode tab 20 includes a first segment 21 extending beyond the separator 13, and the second electrode tab 30 includes a second segment 31 extending beyond the separator 13. A first insulating member 50 is located between the first segment 21 and the second segment 31, connecting the first segment 21 and the second segment 31. The first segment 21 and the second segment 31 form a first electrical connector 101.

[0054] In some embodiments, when the second tab 30 does not extend beyond the first tab 20, along the first direction X, the projection of the first insulating member 50 overlaps with the projection of the first segment 21, and the projection of the second segment 31 is located within the projection of the first insulating member 50. When the second tab 30 overlaps with the first tab 20, along the first direction X, the projection of the first insulating member 50 overlaps with the projection of the first segment 21, and the projection of the first insulating member 50 overlaps with the projection of the second segment 31.

[0055] In some embodiments, along the first direction X, the projection of the first segment 21 is located within the projection of the first insulating member 50 . The first insulating member 50 extends beyond the first segment 21 , thereby reducing the risk of short circuit between the first segment 21 and the second segment 31 due to assembly tolerance.

[0056] In some embodiments, the first insulating member 50 includes a first insulating adhesive 51 . The first insulating adhesive 51 is bonded to a side of the first section 21 facing the second section 31 . The first insulating adhesive 51 is in contact with or partially overlaps the first protective member 102 .

[0057] In some embodiments, the first insulating member 50 includes a second insulating adhesive 52, which is bonded to a side of the second segment 31 facing the first segment 21. The second insulating adhesive 52 is connected to or partially overlaps with the second protective member 103.

[0058] In some embodiments, the first insulating adhesive 51 and the second insulating adhesive 52 include hot melt adhesive. When the housing 40 is heat-sealed, the first insulating adhesive 51 and the second insulating adhesive 52 adhere to each other.

[0059] See also Figure 5 In some embodiments, the first protective member 102 covers the side of the first electrode tab 20 facing the second electrode tab 30 , and the second protective member 103 covers the side of the second electrode tab 30 facing the first electrode tab 20 .

[0060] The secondary battery 100 includes a first metal piece 60 and a second metal piece 70. The first metal piece 60 is electrically connected to the portion of the first tab 20 extending out of the isolation film 13. The second metal piece 70 is electrically connected to the portion of the second tab 30 extending out of the isolation film 13. In the first direction X, the projection of the first metal piece 60 and the projection of the second metal piece 70 overlap, and the first metal piece 60 is insulatedly connected to the second metal piece 70. The first metal piece 60 and the second metal piece 70 are arranged to be overlapped and insulated, which facilitates the connection of the external electrical equipment, and the compatibility of the secondary battery to the battery compartment is higher compared to the first tab 20 and the second tab 30 extending out of the housing 40 from different positions.

[0061] In some embodiments, the first metal piece 60 and the first tab 20 are arranged in the first direction X, and the second tab 30 and the second metal piece 70 are arranged in the first direction X. That is, the portion of the first tab 20 and the second tab 30 extending out of the isolation film 13 is located between the first metal piece 60 and the second metal piece 70, which facilitates the welding connection of the first metal piece 60 and the first tab 20, and facilitates the welding connection of the second metal piece 70 and the second tab 30.

[0062] In some embodiments, the secondary battery 100 includes a second insulating piece 80, which is arranged between the first metal piece 60 and the second metal piece 70. The second insulating piece 80 connects the first metal piece 60 and the second metal piece 70, and forms a second electrical connecting piece 104. The second electrical connecting piece 104 extends out of the housing 40. By increasing the first metal piece 60 and the second metal piece 70, the area of the second electrical connecting piece 104 sealed with the housing 40 is increased, and the sealing effect is improved. The first metal piece 60 and the second metal piece 70 are external standard pieces, and the first metal piece 60, the second metal piece 70 and the second insulating piece 80 can be pre-assembled as a whole, which facilitates the complete overlap of the first metal piece 60 and the second metal piece 70, makes the portion of the second electrical connecting piece 104 extending out of the housing 40 more orderly, and facilitates the connection of the external electrical equipment.

[0063] In some embodiments, the secondary battery 100 includes a third insulating glue 150, which covers the welding mark formed by the welding of the first metal piece 60 and the first tab 20.

[0064] In some embodiments, the secondary battery 100 includes a fourth insulating glue 160, which covers the welding mark formed by the welding of the second metal piece 70 and the second tab 30.

[0065] Please refer to Figure 7 and Figure 8In some embodiments, the shell 40 is provided with a recess 41, and the first electrical connecting member 101 or the second electrical connecting member 104 extends out of the shell 40 from the recess 41, so that the position of the first electrical connecting member 101 or the second electrical connecting member 104 can be adjusted according to the structure of the shell 40, and the compatibility of the battery compartment is improved. Compared with the first and second pole ears 20 and 30 extending out of the shell 40 from different positions, the space occupied by the pole ear extension part is reduced, and the energy density is improved.

[0066] Optionally, the recess 41 is located at the end of the shell 40. Optionally, the recess 41 is located at the middle position of the shell 40.

[0067] Please refer to Figure 9 The application also provides a power consumption device 200 using at least one secondary battery 100. The power consumption device 200 includes a power consumption device body, and the secondary battery 100 is electrically connected to the power consumption device body. In an embodiment, the power consumption device 200 of the application can be, but is not limited to, a mobile phone, a tablet computer, a notebook computer, an industrial PDA, a drone, a backup power supply, an electric vehicle, an electric motorcycle, an electric power-assisted bicycle, an electric tool, etc.

[0068] Those skilled in the art should recognize that the above embodiments are only used to illustrate the application, and are not used as a limitation of the application. Any appropriate changes and variations made to the above embodiments within the spirit and principles of the application fall within the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: The electrode assembly includes a first electrode sheet and a second electrode sheet having opposite polarities, wherein the first electrode sheet and the second electrode sheet are wound; a first pole lug connected to the first pole piece; a second pole tab, connected to the second pole piece; Along the thickness direction of the electrode assembly, the first electrode tab and the second electrode tab are respectively located in adjacent layers of the electrode assembly; a first empty foil groove is provided on the side of the first electrode sheet facing the second electrode sheet, and the first electrode tab is arranged in the first empty foil groove; a second empty foil groove is provided on the side of the second electrode sheet facing the first electrode sheet, and the second electrode tab is arranged in the second empty foil groove; the first electrode tab is insulated from the second electrode tab; Along the thickness direction of the electrode assembly, the projection of the first empty foil slot and the projection of the second empty foil slot at least partially overlap.

2. The secondary battery according to claim 1, wherein The first pole piece is a positive pole piece, and the second pole piece is a negative pole piece.

3. The secondary battery according to claim 1 or 2, wherein: Along the thickness direction of the electrode assembly, the projection of the second empty foil slot is located within the projection of the first empty foil slot.

4. The secondary battery according to claim 1, wherein Along the thickness direction of the electrode assembly, the projection of the second electrode tab is separated from the projection of the edge of the first empty foil groove.

5. The secondary battery according to claim 4, wherein Along the winding direction of the electrode assembly, the distance between the projection of the second electrode tab and the edge of the first empty foil slot is h, 1mm≤h≤5mm.

6. The secondary battery according to claim 1, wherein Along the thickness direction of the electrode assembly, the projection of the second electrode tab does not exceed the projection of the first electrode tab, and the first electrode tab and the second electrode tab are insulated and connected to form a first electrical connector.

7. The secondary battery according to claim 6, wherein The first electrode tab includes a first section extending out of the electrode assembly, and the second electrode tab includes a second section extending out of the electrode assembly; The secondary battery includes a first insulating member located between the first segment and the second segment, the first insulating member connecting the first segment and the second segment, and the first segment and the second segment forming the first electrical connection member.

8. The secondary battery according to claim 7, wherein The secondary battery includes a shell, the electrode assembly is disposed in the shell, and the first electrical connector extends out of the shell.

9. The secondary battery according to claim 7, characterized in that: The first tab is welded to the first empty foil slot to form a first weld mark, and the secondary battery includes a first protective member, the first protective member covers the first weld mark, and the first protective member is connected to the first insulating member; And / or, the second tab is welded to the second empty foil slot to form a second weld mark, the secondary battery includes a second protective member, the second protective member covers the second weld mark, and the second protective member is connected to the first insulating member.

10. The secondary battery according to any one of claims 1 to 9, wherein The secondary battery includes: a first metal member electrically connected to a portion of the first tab extending out of the electrode assembly; a second metal member electrically connected to a portion of the second tab extending out of the electrode assembly; Along the thickness direction of the electrode assembly, the projection of the first metal member and the projection of the second metal member overlap, and the first metal member is insulated and connected to the second metal member.

11. The secondary battery according to claim 10, wherein The secondary battery includes a second insulating member, the second insulating member is provided between the first metal member and the second metal member, the second insulating member connects the first metal member and the second metal member to form a second electrical connector; The secondary battery includes a shell, the electrode assembly is disposed in the shell, and the second electrical connector extends out of the shell.

12. The secondary battery according to claim 8 or 11, wherein The housing is provided with a recess, and the first electrical connector or the second electrical connector extends out of the housing from the recess.

13. An electrical device, characterized in that: The secondary battery according to any one of claims 1 to 12 is included.

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