Battery cell and electrochemical device

Abstract

A second electrode assembly is arranged on the outer side of a first electrode assembly, tabs are electrically connected with the first electrode assembly and the second electrode assembly respectively, meanwhile, a current collector in the second electrode assembly is an empty foil without an active material layer, and when the second electrode assembly is short-circuited, the current collector is electrically connected with the first electrode assembly and the second electrode assembly. The current originally flowing through the failure point of the battery is absorbed by a short-circuit loop of the second electrode assembly, so that the current flowing through the failure point of the battery is reduced, and the heat generated at the failure point is reduced; and the second electrode assembly can play a role in shunting, so that the current flowing through the short circuit point is further reduced, and in addition, the discharge speed is accelerated, thereby improving the safety.

Description

Technical Field

[0001] The utility model relates to the technical field of electrochemistry, in particular to an electric core and an electrochemical device provided with the electric core. Background Art

[0002] With the development of science and technology, batteries have become an indispensable part of our daily lives. From mobile phones and laptops to electric vehicles and large-scale grid energy storage, batteries play an important role. However, with the widespread popularity of battery applications, safety issues have become increasingly prominent. This is not only related to the safety of the equipment, but also to the life safety of the user and the stability of the entire society. Therefore, battery application safety is of great significance. As an energy storage device, batteries have advantages such as high energy density and portability, but they also have certain safety hazards. For example, overcharging, over-discharging, external short circuit, internal short circuit and other problems may lead to safety accidents such as battery fire and explosion.

[0003] During daily use or assembly, when lithium-ion batteries are subjected to mechanical abuse such as impact, drop, or extrusion, they may cause a vicious short circuit inside the battery, triggering local hot spots and electrochemical reactions. The superposition effect leads to thermal runaway and fire failure of the battery. Current means of improving safety include more stable positive and negative electrode materials, electrolyte additives, and safety coatings, but these measures will lose other battery properties, such as cycle capacity attenuation, multiple charge and discharge, and volume and mass energy density.

[0004] Therefore, how to improve the safety performance, high and low temperature performance, and charge and discharge rate performance of batteries under various malicious mechanical abuses is a technical problem that needs to be solved urgently. Utility Model Content

[0005] In view of this, the purpose of the present invention is to provide a battery cell and an electrochemical device for solving the problem of how to improve the safety performance of the battery cell under mechanical abuse.

[0006] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0007] A battery cell, comprising a first electrode assembly, the first electrode assembly comprising a first pole piece, a second pole piece, and a first isolation film disposed between the first pole piece and the second pole piece, the first pole piece comprising a first current collector and a first active material layer disposed on a surface of the first current collector, the second pole piece comprising a second current collector and a second active material layer disposed on a surface of the second current collector;

[0008] The battery cell further includes a second electrode assembly, the second electrode assembly includes a third electrode sheet, a fourth electrode sheet, and a second isolation film disposed between the third electrode sheet and the fourth electrode sheet, the third electrode sheet includes a third current collector without an active material layer, the fourth electrode sheet includes a fourth current collector without an active material layer, and the second electrode assembly is disposed outside the first electrode assembly;

[0009] The battery cell further includes a first pole tab and a second pole tab, wherein the first pole tab is electrically connected to the first current collector and the third current collector, respectively, and the second pole tab is electrically connected to the second current collector and the fourth current collector, respectively.

[0010] Optionally, in the above battery cell, a tab transfer structure is further included, wherein the tab transfer structure includes a tab body, a first portion and a second portion;

[0011] The first portion and the second portion are respectively connected to the fixed ends of the tab body, the first portion is electrically connected to the first electrode assembly, and the second portion is electrically connected to the second electrode assembly.

[0012] Optionally, in the above-mentioned battery core, an insulating layer is provided inside the first part and the second part;

[0013] And / or, the tab body is provided with tab glue.

[0014] Optionally, in the above battery cell, on the projection of the battery cell in the second direction, the length of the second portion is H1,5 mm

[0015] Optionally, in the above-mentioned battery cell, the first current collector and the third current collector are integrally formed into a fifth current collector, the second current collector and the fourth current collector are integrally formed into a sixth current collector, the first isolation film and the second isolation film are integrally formed into a third isolation film, and the fifth current collector, the third isolation film and the sixth current collector are stacked and wound to form a core.

[0016] Optionally, in the above-mentioned battery cell, the total number of folds of the winding core is n, the number of the second electrode assemblies is m, the number of the first electrode tabs is N, and 0<N≤nm;

[0017] The number of the first electrode tabs is equal to the number of the second electrode tabs.

[0018] ​Optionally, in the above-mentioned battery cell, when N is 1, the first pole lug is located at the innermost head of the winding core; the second pole lug is located at the innermost head of the winding core, the first part of one pole lug transition structure is connected to the first pole lug, and the first part of another pole lug transition structure is connected to the second pole lug;

[0019] Alternatively, when 1≤N<nm, the innermost side of the winding core is the first fold, the first pole lug is located at any position except the first fold, the second pole lug is located at any position except the first fold, the first portion of one pole lug transition structure is connected to the first pole lug, and the first portion of another pole lug transition structure is connected to the second pole lug;

[0020] Alternatively, when N=nm, the first portion of one of the tab transfer structures is connected to a plurality of the first tabs, and the first portion of another of the tab transfer structures is connected to a plurality of the second tabs.

[0021] Optionally, in the above battery cell, the first current collector at least partially protrudes along a first direction to form a first region, and the second current collector at least partially protrudes along the first direction to form a second region;

[0022] Wherein, the first portion of one of the tab transition structures is integrally arranged with the first region, or the first portion of one of the tab transition structures is welded with the first region;

[0023] And / or, the first portion of another of the tab transition structures is integrally arranged with the second region, or the first portion of another of the tab transition structures is welded to the second region.

[0024] Optionally, in the above battery cell, the battery cell comprises a plurality of the first electrode assemblies and the second electrode assemblies stacked in sequence;

[0025] The first electrode tab is electrically connected to a plurality of the first current collectors and the third current collector, and the second electrode tab is electrically connected to a plurality of the second current collectors and the fourth current collector.

[0026] Optionally, in the above battery cell, the second electrode assembly is at least arranged on two sides of the first electrode assembly along the second direction.

[0027] Optionally, in the above battery cell, along the first direction, at least a portion of the second electrode assembly is bent and extended to the top of the first electrode assembly to form a protruding area, and the second portions of the first electrode lug and the second electrode lug are both electrically connected to the protruding area.

[0028] Optionally, in the above battery cell, 0 <W1<40mm;0<T1<1mm。

[0029] An electrochemical device comprises the above-mentioned battery cell.

[0030] It can be seen from the above technical solution that in the battery cell provided by the utility model, the second electrode assembly is arranged on the outside of the first electrode assembly, and the pole ears are electrically connected to the first electrode assembly and the second electrode assembly respectively. At the same time, the current collector in the second electrode assembly is a hollow foil without an active material layer. When the second electrode assembly is short-circuited, the original current flowing through the failure point of the battery is absorbed by the short-circuit loop of the second electrode assembly, and then the current flowing through the failure point of the battery is reduced, and the heat generation at the failure point is reduced; and the second electrode assembly can play a role of shunting, so that the current flowing through the short-circuit point is further reduced, and the discharge speed is also accelerated, thereby improving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the conventional structure of the winding core provided in the first embodiment of the present utility model;

[0033] Figure 2 A schematic diagram of the structure of a pole piece punched to form a pole ear provided in an embodiment of the utility model;

[0034] Figure 3 A top view of the connection between the pole tab connection area formed by pole piece washing and the pole tab transfer structure provided in an embodiment of the utility model;

[0035] Figure 4 A schematic diagram of the structure of welding the connecting sheet and the second electrode assembly provided in an embodiment of the utility model;

[0036] Figure 5 A schematic diagram of the structure of the tab adapter structure provided in the fifth embodiment of the present utility model;

[0037] Figure 6 A schematic diagram of the structure of the tab adapter structure provided in the sixth embodiment of the present utility model;

[0038] Figure 7 A schematic diagram of the structure of the second electrode assembly in the stacked core provided in an embodiment of the utility model;

[0039] Figure 8 A top view of the second electrode assembly and the first electrode assembly in the stacked core provided by an embodiment of the utility model;

[0040] Fig. 9 This is a side view of the battery cell provided in the tenth and eleventh embodiments of the present utility model.

[0041] in:

[0042] 1- a first electrode assembly,

[0043] 11-first current collector, 111-first region, 12-second current collector, 121-second region,

[0044] 2-second electrode assembly, 21-third current collector, 22-fourth current collector, 23-second isolation film,

[0045] 31-ear body, 32-first part, 33-second part, 34-ear glue. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0047] In the description of the utility model, it should be noted that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the utility model product is usually placed when in use, and are only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0048] like Figures 1 to 9 As shown, an embodiment of the utility model provides a battery cell.

[0049] First, the battery cell includes a first electrode assembly 1, a second electrode assembly 2, a first pole ear and a second pole ear, wherein the first electrode assembly 1 includes a first pole piece, a second pole piece, and a first isolation membrane arranged between the first pole piece and the second pole piece, the first pole piece includes a first current collector 11 and a first active material layer arranged on the surface of the first current collector 11, and the second pole piece includes a second current collector 12 and a second active material layer arranged on the surface of the second current collector 12; the second electrode assembly 2 includes a third pole piece, a fourth pole piece, and a second isolation membrane 23 arranged between the third pole piece and the fourth pole piece, the third pole piece includes a third current collector 21 without an active material layer, the fourth pole piece includes a fourth current collector 22 without an active material layer, and the second electrode assembly 2 is arranged on the outside of the first electrode assembly 1; the first pole ear is electrically connected to the first current collector 11 and the third current collector 21 respectively, and the second pole ear is electrically connected to the second current collector 12 and the fourth current collector 22 respectively.

[0050] It should be noted that the first electrode assembly 1 includes a stacked plurality of first pole pieces, a second pole piece, and a first isolation film disposed between the first pole piece and the second pole piece, and the outside refers to the outermost pole piece or the outer surface of the first isolation film.

[0051] It can be seen that in the battery cell provided by the embodiment of the utility model, the second electrode assembly 2 is arranged on the outside of the first electrode assembly 1, and the pole ears are electrically connected to the first electrode assembly 1 and the second electrode assembly 2 respectively. At the same time, the current collector in the second electrode assembly 2 is a hollow foil without an active material layer. When the second electrode assembly 2 is short-circuited, the original current flowing through the battery failure point is absorbed by the short-circuit loop of the second electrode assembly 2, and then the current flowing through the battery failure point is reduced, and the heat generation at the failure point is reduced; and the second electrode assembly 2 can play a role of shunting, so that the current flowing through the short-circuit point is further reduced, and the discharge speed is also accelerated, thereby improving safety.

[0052] In a specific implementation, it also includes a pole tab transfer structure, which includes a pole tab body 31, a first part 32 and a second part 33; the fixed ends of the pole tab body 31 are respectively connected to the first part 32 and the second part 33, the first part 32 is electrically connected to the first electrode assembly 1, and the second part 33 is electrically connected to the second electrode assembly 2.

[0053] See also Figure 5 The tab body 31 , the first portion 32 and the second portion 33 are integrally formed into a Y-shaped tab, which simplifies the structure.

[0054] In a specific implementation, an insulating layer is provided inside the first portion 32 and the second portion 33 to prevent the tab transfer structure from contacting the pole piece of the battery cell and causing a short circuit in the battery.

[0055] It should be noted that the insulating layer is disposed on the opposite inner surfaces of the first portion 32 and the second portion 33 .

[0056] It should be noted that the insulating layer can be glue or adhesive tape, and the specific material type is not specifically limited. Those skilled in the art can make specific designs according to actual needs.

[0057] During specific implementation, the tab body 31 is provided with tab glue 34. The tab glue 34 is arranged at the root position of one end of the tab body 31 close to the battery cell side. The tab glue 34 covers the upper surface and the lower surface of the root position of the tab body 31 respectively, and is used for encapsulating the battery cell.

[0058] During specific implementation, in the projection in the second direction of the battery cell, the length of the second part 33 is H1, 5mm < H1 < 100mm; the width is W1, 0 < W1 < 100mm; the thickness is T1, 0 < T1 < 3mm; preferably, 0 < W1 < 40mm; 0 < T1 < 1mm.

[0059] With such a setting, the current-carrying capacity of the tab转接 structure can be ensured, and the second part 33 is not easily melted, thereby improving safety; in addition, the occupied space of the second part 33 can be reduced, and the energy density of the battery cell can be increased. In addition, those skilled in the art can also make specific designs for the specific dimensions of the second part 33 according to actual needs.

[0060] Particularly, in the field of small-sized 3C consumer batteries, the dimensions of the length and width of the second part 33 can be 0 < W1 < 40mm; 0 < T1 < 1mm. It can play a safety role and avoid material waste at the same time.

[0061] During specific implementation, the second part 33 is welded to the second electrode assembly 2 to form a welding area. The length of the welding area is H2, H2 ≤ H1; the welding width is W2, W2 ≤ W1. It should be noted that the welding connection can be ultrasonic welding or laser welding, but it is not limited thereto. Those skilled in the art can make specific designs according to actual needs.

[0062] During specific implementation, the first current collector 11 and the third current collector 21 are integrally formed into a fifth current collector, the second current collector 12 and the fourth current collector 22 are integrally formed into a sixth current collector, the first separator and the second separator 23 are integrally formed into a third separator, and the fifth current collector, the third separator and the sixth current collector are laminated and wound to form a wound core.

[0063] In this way, on the one hand, the manufacturing efficiency of the battery cell can be improved, and on the other hand, the internal resistance at the welding joint when the first current collector 11 and the third current collector 21 or the second current collector 12 and the fourth current collector 22 are welded can be reduced, thereby reducing the heat generation at the welding joint and improving the flatness of the battery cell.

[0064] In a specific implementation, the total number of folds of the winding core is n, the number of the second electrode assemblies 2 is m, the number of the first pole ears is N, 0<N≤nm; the number of the first pole ears is equal to the number of the second pole ears. It should be noted that in the winding core structure, the winding tails of the fifth current collector and the sixth current collector are respectively exposed current collectors (i.e., no active material layer is provided), and the exposed current collectors and the third isolation film are wound to form the second electrode assembly 2; and / or, the winding middle parts of the fifth current collector and the sixth current collector are respectively exposed current collectors, and the exposed current collectors and the third isolation film are wound to form the second electrode assembly 2.

[0065] In a specific implementation, one of the first electrode sheet and the second electrode sheet is a negative electrode sheet, and the other is a positive electrode sheet, and the size of the second separator is larger than that of the negative electrode sheet. The negative electrode active material layer can cover the positive electrode active material layer to prevent the positive electrode active material from being embedded in the structure of the negative electrode active material, thereby preventing lithium precipitation.

[0066] Specifically, during implementation, the first isolation film of the first electrode assembly 1 is disposed between the first pole piece and the second pole piece, and the first electrode assembly 1 is wound to form a winding core. Two first isolation films are required during the winding process of the winding core, which are respectively located on both sides of the first pole piece, or respectively located on both sides of the second pole piece. The two first isolation films are wound 0.5 to 2 turns at the starting end of the winding. The two first isolation films are wound first to prevent short circuits inside the winding core.

[0067] In specific implementation, a fixing layer is provided at the tail of the exposed current collector of the outermost winding of the winding core. The fixing layer may be adhesive tape or other materials. Those skilled in the art may make a specific design according to actual needs.

[0068] In specific implementation, the first current collector 11 in the core structure includes a single-sided coating area and a double-sided coating area. The single-sided coating area is the first current collector 11 and the active material layer arranged on one surface of the first current collector 11, and the double-sided coating area is the first current collector 11 and the active material layer arranged on both surfaces of the first current collector 11. The empty foil surface of the single-sided coating area faces the inner side of the core; the second current collector 12 in the core structure includes a single-sided coating area and a double-sided coating area. The single-sided coating area is the second current collector 12 and the active material layer arranged on one surface of the second current collector 12, and the double-sided coating area is the second current collector 12 and the active material layer arranged on both surfaces of the second current collector 12. The empty foil surface of the single-sided coating area faces the inner side of the core; one of the first current collector 11 and the second current collector 12 is a copper foil, and the other is an aluminum foil.

[0069] In a specific implementation, the lead-out positions of the tabs in the winding core structure may be consistent or staggered in the thickness direction of the battery cell.

[0070] In a specific implementation, when N is 1, the first pole tab is located at the innermost head of the winding core; the second pole tab is located at the innermost head of the winding core, the first portion 32 of one pole tab transition structure is connected to the first pole tab, and the first portion 32 of another pole tab transition structure is connected to the second pole tab, forming a conventional structure;

[0071] Alternatively, when 1≤N<nm, the innermost side of the winding core is the first fold, the first pole lug is located at any position except the first fold, the second pole lug is located at any position except the first fold, the first portion 32 of one pole lug transition structure is connected to the first pole lug, and the first portion 32 of another pole lug transition structure is connected to the second pole lug, forming a pole lug center structure;

[0072] Alternatively, when N=nm, the first portion 32 of one tab transition structure is connected to a plurality of first tabs, and the first portion 32 of another tab transition structure is connected to a plurality of second tabs, forming a multi-tab structure.

[0073] In a specific implementation, the first current collector 11 at least partially protrudes along the first direction to form a first area 111, and the second current collector 12 at least partially protrudes along the first direction to form a second area 121; wherein, the first portion 32 of a tab transition structure is integrally arranged with the first area 111, or the first portion 32 of a tab transition structure is welded to the first area 111; and / or, the first portion 32 of another tab transition structure is integrally arranged with the second area 121, or the first portion 32 of another tab transition structure is welded to the second area 121. The battery head space can be reasonably used to reduce the thickness of the tab occupying the overall thickness of the battery and improve the battery energy density. It should be noted that the first current collector 11 is formed into a structure with a first area 111 by punching; the second current collector 12 is formed into a structure with a second area 121 by punching, but it is not limited to this. The structural form of the local protrusion of the current collector can be specifically designed by those skilled in the art according to actual needs.

[0074] During specific implementation, the first pole piece is cleaned and coated with the active coating on the first current collector 11, exposing the first current collector 11 to form a first cleaning zone, and the first part 32 of a pole ear transition structure is connected to the first cleaning zone; the second pole piece is cleaned and coated with the active coating on the second current collector 12, exposing the second current collector 12 to form a second cleaning zone, and the first part 32 of another pole ear transition structure is connected to the second cleaning zone.

[0075] In a specific implementation, the battery cell includes a plurality of first electrode assemblies 1 and second electrode assemblies 2 stacked in sequence, i.e., forming a stacked core structure; wherein the first pole tab is electrically connected to a plurality of first current collectors 11 and a third current collector 21, and the second pole tab is electrically connected to a plurality of second current collectors 12 and a fourth current collector 22.

[0076] In a specific implementation, the third pole piece is a positive pole piece, the fourth pole piece is a negative pole piece, the second portion 33 of the pole tab transition structure connected to the third pole piece includes one or both of aluminum and nickel, and the second portion 33 of the pole tab transition structure connected to the fourth pole piece includes one or both of copper and nickel, but is not limited thereto. The specific material of the second portion 33 of the pole tab transition structure can be specifically designed by a person skilled in the art according to actual needs. In addition, the third pole piece 11 can also be a negative pole piece, and the fourth pole piece 12 can be a positive pole piece, and the material type of the second portion 33 of the corresponding pole tab transition structure can be adjusted according to the positive and negative pole pieces to which it is connected.

[0077] In a specific implementation, the second electrode assembly 2 is at least provided on both sides of the first electrode assembly 1 along the second direction. It should be noted that the second direction is the thickness direction of the battery cell. When the battery cell is a roll core, during the winding process of the roll core, the empty foil area at the tail of the fifth current collector surrounds the roll core at least one circle (i.e., two folds), and the empty foil area at the tail of the sixth current collector surrounds the roll core at least one circle (i.e., two folds). The empty foil area at the tail of the fifth current collector and the empty foil area at the tail of the sixth current collector both surround the roll core at least one circle, so that after any side of the roll core is damaged by mechanical parts, the empty foil surfaces of the empty foil area at the tail of the fifth current collector and the empty foil area at the tail of the sixth current collector are preferentially short-circuited to release battery energy.

[0078] When the battery cell is stacked, the second electrode assembly 2 is located on the upper and lower sides of the thickness direction of the battery cell. However, it is not limited to this. A plurality of second electrode assemblies 2 are provided, and the second electrode assembly 2 is provided at the outermost side of the first electrode assembly 1. If there are too few second electrode assemblies 2, the third current collector 21 and the fourth current collector 22 will be too thin to have insufficient current capacity during short circuit, and the short circuit damage point will be melted, making it impossible to continue short circuiting. If there are too many second electrode assemblies 2, the thickness of the battery cell will increase and the battery energy density will be lost. The specific number and setting position of the second electrode assembly 2 can be specifically designed by those skilled in the art according to actual needs. In addition, the empty foil area at the tail of the fifth current collector and the empty foil area at the tail of the sixth current collector can also surround the core half a circle (i.e., one fold) to protect one side of the core from being damaged by mechanical parts.

[0079] For specific implementation, see Fig. 9 Along the first direction, at least part of the second electrode assembly 2 is bent and extended to the top of the first electrode assembly 1 to form a protruding area, and the second parts 33 of the first pole ear and the second pole ear are electrically connected to the protruding area to form a connecting portion, and the connecting portion is folded along the edge of the first electrode assembly 1 toward the second direction and close to one side of the battery cell, which can reasonably utilize the head space of the multi-pole ear battery, reduce the thickness of the pole ear occupied by the overall thickness of the battery, and improve the battery energy density.

[0080] An embodiment of the utility model provides an electrochemical device, comprising the above-mentioned battery cell.

[0081] It can be seen that the second electrode assembly 2 of the battery cell in the electrochemical device provided in the embodiment of the utility model is arranged on the outside of the first electrode assembly 1, and the pole ears are electrically connected to the first electrode assembly 1 and the second electrode assembly 2 respectively. At the same time, the current collector in the second electrode assembly 2 is a hollow foil without an active material layer. When the second electrode assembly 2 is short-circuited, the original current flowing through the failure point of the battery is absorbed by the short-circuit loop of the second electrode assembly 2, and then the current flowing through the failure point of the battery is reduced, and the heat generation at the failure point is reduced; and the second electrode assembly can play a role of shunting, so that the current flowing through the short-circuit point is further reduced, and the discharge speed is also accelerated, thereby improving safety.

[0082] The electronic equipment of the present invention is not particularly limited, and may include but is not limited to: laptop computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

[0083] According to the different structures of the battery cells and the sizes of the connecting pieces, the following examples and comparative data analysis were performed:

[0084] Example 1

[0085] like Figure 1 As shown, embodiment 1 of the utility model provides a battery cell, wherein the first electrode assembly 11 includes a first electrode piece and a second electrode piece, wherein the first electrode piece is cleaned and coated with an active coating on the first current collector 11, exposing the first current collector 11 to form a first cleaning area; the second electrode piece is cleaned and coated with an active coating on the second current collector 12, exposing the second current collector 12 to form a second cleaning area.

[0086] In a specific implementation, the tab transfer structure includes a tab body 31, a first portion 32 and a second portion 33, the fixed ends of the tab body 31 are respectively connected to the first portion 32 and the second portion 33, the first portion 32 is electrically connected to the first electrode assembly 1, the second portion 33 is electrically connected to the second electrode assembly 2, and the first portion 32 and the tab body 31 are an integrated structure tab area;

[0087] The first portion 32 of one tab transfer structure is connected to the first cleaning zone, and the first portion 32 of the other tab transfer structure is connected to the second cleaning zone.

[0088] In a specific implementation, the first current collector 11 and the third current collector 21 are integrally formed into a fifth current collector, the second current collector 12 and the fourth current collector 22 are integrally formed into a sixth current collector, the first isolation film and the second isolation film 23 are integrally formed into a third isolation film, and the fifth current collector, the third isolation film and the sixth current collector are stacked and wound to form a winding core;

[0089] In a specific implementation, the total number of folds of the winding core is n, the number of the second electrode assemblies 2 is m, the number of the first electrode tabs is N, and 0<N≤nm;

[0090] The number of the first electrode tabs is equal to the number of the second electrode tabs.

[0091] In specific implementation, when N is 1, the first pole ear is located at the innermost head of the winding core; the second pole ear is located at the innermost head of the winding core, the first part 32 of one pole ear transition structure is connected to the first pole ear, and the first part 32 of the other pole ear transition structure is connected to the second pole ear.

[0092] In a specific implementation, the empty foil area at the tail of the fifth current collector surrounds the winding core once (ie, folds twice), and the empty foil area at the tail of the sixth current collector surrounds the winding core once (ie, folds twice).

[0093] In specific implementation, in the projection of the second direction of the battery cell, the width W1 of the second portion 33 is 6 mm, which is consistent with the width of the tab body 31, the length H1 is 15 mm, and the thickness T1 is 20 μm. The insulating layer is an insulating glue with a thickness of 15 μm. The welding position of the second portion 33 is consistent with the position of the current collector on the first electrode assembly 1 in the thickness direction of the battery cell, which facilitates the welding operation.

[0094] In a specific implementation, the second portion 33 is welded to the second electrode assembly 2 to form a welding zone, wherein the welding is performed by laser welding, the welding width W2 of the welding zone is 6 mm, and the welding length H2 is 8 mm.

[0095] Example 2

[0096] The second embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0097] In specific implementation, the thickness T1 of the second portion 33 is 100 μm. This design can enhance the current carrying capacity of the connecting sheet, prevent the tab from overheating or even melting when the second electrode assembly 2 actively triggers a short circuit, and reduce the transmission resistance of the second electrode assembly 2 short circuit, thereby achieving better shunt effect and improving the safety of the battery.

[0098] Example 3

[0099] The third embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0100] In specific implementation, the width W1 of the second portion 33 is 10 mm, and the thickness T1 is 100 μm. This design can further enhance the current carrying capacity of the connecting piece, prevent the tab from overheating or even melting when the second electrode assembly 2 actively triggers a short circuit, and reduce the transmission resistance of the second electrode assembly 2 short circuit, thereby achieving a better shunt effect and improving the safety of the battery.

[0101] Example 4

[0102] The fourth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0103] In a specific implementation, the welding length H2 of the welding area is 10 mm, which can reduce the welding contact resistance between the connecting sheet and the battery core and reduce the heating of the pole piece.

[0104] Example 5

[0105] like Figure 5 As shown, the fifth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0106] During specific implementation, the pole ear body 31, the first part 32, and the second part 33 are an integrated structure, that is, the pole ear transition structure is an integral structural member; the pole ear body 31 is provided with a pole ear glue 34. The pole ear glue 34 is set at the root position of the pole ear body 31 close to one end of the battery cell side. The pole ear glue 34 covers the upper and lower surfaces of the root position of the pole ear body 31 respectively, and is used to encapsulate the battery cell. It should be noted that since the winding core is a conventional structure, that is, the first pole piece and the second pole piece each contain only one pole ear, the pole ear transition structure of the integrated structure is Y-shaped. At the same time, an insulating layer is provided on the side of the integrated structure close to the battery cell to ensure that the connecting piece does not contact the positive and negative pole pieces at the top sealing position to prevent short circuit. This design can effectively simplify the manufacturing process of the structure, while reducing the thickness of the battery and reducing energy loss.

[0107] Example 6

[0108] like Figure 6 As shown, the sixth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0109] In a specific implementation, the tab body 31, the first part 32, and the second part 33 are an integrated structure, that is, the tab transfer structure is an integral structural member; the tab body 31 is provided with a tab glue 34. The tab glue 34 is provided at the root position of the tab body 31 close to one end of the battery cell side. The tab glue 34 covers the upper surface and the lower surface of the root position of the tab body 31 respectively, and is used to encapsulate the battery cell.

[0110] In a specific implementation, the first pole piece includes two first pole tabs, and the second pole piece includes two second pole tabs, so that the pole tab transition structure of the integrated structure is E-type. This design can further enhance the shunting effect of the second electrode assembly 2 .

[0111] Example 7

[0112] The seventh embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0113] In a specific implementation, the first insulating layer is ceramic with a thickness of 10 μm.

[0114] Exemplary Embodiment Eight

[0115] The eighth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0116] In specific implementation, when 1≤N<nm, the innermost side of the winding core is the first fold, the first pole ear 111 is located at any position except the first fold, and the second pole ear 121 is located at any position except the first fold, forming a pole ear center structure. Compared with the structure of the first embodiment, its mechanical safety test has a better effect, and at the same time, the safety test of the battery with the pole ear center structure is also significantly improved.

[0117] Exemplary Embodiment Nine

[0118] like Figure 7 , Figure 8 As shown, the ninth embodiment of the present utility model provides a battery cell which is generally different from the first embodiment described above in that:

[0119] In a specific implementation, the battery cell includes a plurality of first electrode assemblies 1 and second electrode assemblies 2 stacked in sequence, i.e., forming a stacked core structure; wherein the first pole tab is electrically connected to a plurality of first current collectors 11 and a third current collector 21, and the second pole tab is electrically connected to a plurality of second current collectors 12 and a fourth current collector 22.

[0120] In a specific implementation, the second electrode assembly 2 covers the upper and lower sides of the stacked core.

[0121] Compared with the battery cell structure in Example 1, the mechanical safety test has better results, and also has obvious improvements compared with the safety test of multi-electrode structure batteries.

[0122] Exemplary Embodiment 10

[0123] The tenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0124] In a specific implementation, when N=nm, the first portion 32 of one tab transition structure is connected to a plurality of first tabs, and the first portion 32 of another tab transition structure is connected to a plurality of second tabs, forming a multi-tab structure.

[0125] In specific implementation, along the first direction, at least part of the second electrode assembly 2 is bent and extended to the top of the first electrode assembly 1 to form a protruding area, and the first pole tab and the second portion 33 of the second pole tab are both electrically connected to the protruding area. The protruding length along the first direction is 2 mm.

[0126] In a specific implementation, the second portion 33 has a width W1 of 10 mm, a length H1 of 15 mm, and a thickness T1 of 100 μm.

[0127] In specific implementation, the welding width W2 of the welding area is 10 mm, and the welding length H2 is 2 mm. The head space of the multi-tab battery can be reasonably utilized, the thickness of the tab occupies the overall thickness of the battery, and the battery energy density is improved.

[0128] Exemplary Embodiment Eleven

[0129] The eleventh embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0130] In a specific implementation, the battery cell includes a plurality of first electrode assemblies 1 and second electrode assemblies 2 stacked in sequence, i.e., forming a stacked core structure; wherein the first pole tab is electrically connected to a plurality of first current collectors 11 and a third current collector 21, and the second pole tab is electrically connected to a plurality of second current collectors 12 and a fourth current collector 22.

[0131] In specific implementation, along the first direction, at least part of the second electrode assembly 2 is bent and extended to the top of the first electrode assembly 1 to form a protruding area, and the first pole tab and the second portion 33 of the second pole tab are both electrically connected to the protruding area. The protruding length along the first direction is 2 mm.

[0132] In a specific implementation, the second portion 33 has a width W1 of 10 mm, a length H1 of 15 mm, and a thickness T1 of 100 μm.

[0133] In specific implementation, the welding width W2 of the welding area is 10 mm, and the welding length H2 is 2 mm. The head space of the multi-tab battery can be reasonably utilized, the thickness of the tab occupies the overall thickness of the battery, and the battery energy density is improved.

[0134] Exemplary Embodiment Twelve

[0135] The twelfth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0136] In specific implementation, the empty foil area at the tail of the fifth current collector surrounds the winding core 0.5 times (i.e., one fold), and the empty foil area at the tail of the sixth current collector surrounds the winding core 0.5 times (i.e., one fold). This can reduce the thickness of the battery and increase the energy density of the battery.

[0137] Exemplary Embodiment Thirteen

[0138] The thirteenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0139] In specific implementation, the fifth current collector of the winding core leads out the first pole ear in the head empty foil area and the 10th fold respectively. The position of the pole ear is in the same vertical direction of the winding core, and the welding method and welding size are the same as those of the head empty foil area. The sixth current collector leads out the second pole ear in the head empty foil area and the 12th fold respectively. The position of the pole ear is in the same vertical direction of the winding core, and the welding method and welding size are the same as those of the head empty foil area. The first part 32 of one pole ear transition structure is welded to the first pole ear, and the first part 32 of the other pole ear transition structure is welded to the second pole ear. It can increase the shunting effect of the second electrode assembly 2 on the short-circuit point, and the mechanical safety improvement effect is significantly enhanced.

[0140] Exemplary Embodiment Fourteen

[0141] The fourteenth embodiment of the present utility model provides a battery cell which is generally different from the first embodiment described above in that:

[0142] In specific implementation, the fifth current collector of the core leads out the first pole lug in the head empty foil area, the first fold, the third fold, and the fifth fold, respectively. The pole lug positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil area. The sixth current collector of the core leads out the second pole lug in the head empty foil area, the third fold, the fifth fold, and the seventh fold, respectively. The pole lug positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil.

[0143] In a specific implementation, the width W1 of the second portion 33 is 10 mm, and the thickness T1 is 100 μm, which can enhance the current carrying capacity of the tab and prevent the tab from overheating or fusing.

[0144] Exemplary Embodiment Fifteen

[0145] The fifteenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0146] In specific implementation, the fifth current collector of the core leads out the first tab at the head empty foil area, the 13th fold, the 15th fold, and the 17th fold, respectively. The tab positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil area. The sixth current collector of the core leads out the second tab at the head empty foil area, the 15th fold, the 17th fold, and the 19th fold, respectively. The tab positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil.

[0147] In a specific implementation, the width W1 of the second portion 33 is 10 mm, and the thickness T1 is 100 μm, which can enhance the current carrying capacity of the tab and prevent the tab from overheating or fusing.

[0148] Exemplary Embodiment 16

[0149] The sixteenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0150] In specific implementation, the fifth current collector of the core leads out the first tab at the head empty foil area, the 5th fold, the 9th fold, and the 13th fold, respectively. The tab positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil area. The sixth current collector of the core leads out the second tab at the head empty foil area, the 7th fold, the 11th fold, and the 15th fold, respectively. The tab positions are in the same vertical direction of the core, and the welding method and welding size are the same as those of the head empty foil.

[0151] In a specific implementation, the width W1 of the second portion 33 is 10 mm, and the thickness T1 is 100 μm, which can enhance the current carrying capacity of the tab and prevent the tab from overheating or fusing.

[0152] Exemplary Embodiment 17

[0153] The seventeenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0154] In a specific implementation, the first current collector 11 at least partially protrudes along the first direction to form a first area 111, and the second current collector 12 at least partially protrudes along the first direction to form a second area 121; wherein, the first portion 32 of a tab transition structure is integrally arranged with the first area 111, or the first portion 32 of a tab transition structure is welded to the first area 111; and / or, the first portion 32 of another tab transition structure is integrally arranged with the second area 121, or the first portion 32 of another tab transition structure is welded to the second area 121. It should be noted that the first current collector 11 is formed into a structure with the first area 111 by punching; and the second current collector 12 is formed into a structure with the second area 121 by punching.

[0155] In a specific implementation, the fifth current collector of the winding core leads out the first pole tab 111 at the head empty foil area, the fifth fold, the ninth fold, and the thirteenth fold, respectively, and the pole tab positions are in the same vertical direction of the winding core. The sixth current collector of the winding core leads out the second pole tab 121 at the head empty foil area, the seventh fold, the eleventh fold, and the fifteenth fold, respectively, and the pole tab positions are in the same vertical direction of the winding core.

[0156] In a specific implementation, the width W1 of the second portion 33 is 10 mm, and the thickness T1 is 100 μm, which can enhance the current carrying capacity of the tab and prevent the tab from overheating or fusing.

[0157] Exemplary Embodiment 18

[0158] The eighteenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0159] In specific implementation, the third current collector 21 and the second part 33 of one tab transition structure are an integral structure formed by punching; the fourth current collector 22 and the second part 33 of another tab transition structure are an integral structure formed by punching. The width W1 of the punched second part 33 is 6 mm, the length H1 is 10 mm, and the thickness is consistent with the thickness of the third current collector 21 and the fourth current collector 22. It can reduce the energy density loss of the battery.

[0160] In specific implementation, the empty foil area at the tail of the fifth current collector is wrapped around the winding core twice (i.e., four folds), and the empty foil area at the tail of the sixth current collector is wrapped around the winding core twice (i.e., four folds). The double-layer second electrode assembly 2 has a smaller short-circuit resistance and a stronger shunt effect; secondly, the thickness of the tab punched out of the double-layer foil is thicker, the current capacity is strong, and it is not easy to fuse.

[0161] Exemplary Embodiment Nineteen

[0162] The nineteenth embodiment of the present invention provides a battery cell which is generally different from the first embodiment described above in that:

[0163] In a specific implementation, the first current collector 11 is punched to form a first electrode tab, and the second current collector 12 is punched to form a second electrode tab.

[0164] In a specific implementation, the fifth current collector of the winding core leads out the first pole lug 111 in the head empty foil area, the 5th fold, the 9th fold, and the 13th fold, respectively, and the pole lug positions are not in the same vertical direction of the winding core (i.e., they are misaligned). The sixth current collector of the winding core leads out the second pole lug 121 in the head empty foil area, the 7th fold, the 11th fold, and the 15th fold, respectively, and the pole lug positions are not in the same vertical direction of the winding core (i.e., they are misaligned).

[0165] The core is changed from a conventional structure to a multi-electrode ear structure. The positive electrode ears are punched out at the head empty foil, the 5th fold, the 9th fold, and the 13th fold of the positive electrode sheet of the core, and the positions of the ears are not in the same vertical direction of the core. The negative electrode ears are punched out at the head empty foil, the 7th fold, the 11th fold, and the 15th fold of the negative electrode sheet of the core, and the positions of the ears are not in the same vertical direction of the core.

[0166] Comparative Example 1

[0167] The utility model provides a battery cell in comparative example 1, which is generally different from the above-mentioned embodiment 1 in that:

[0168] The first electrode sheet, the first isolation film and the second electrode sheet in the first electrode assembly 1 are stacked and wound to obtain a battery cell.

[0169] Comparative Example 2

[0170] The utility model provides a battery cell in comparative example 2, which is generally different from the above-mentioned embodiment 1 in that:

[0171] An empty foil area is set at the tail of the fifth current collector, and the empty foil area is folded in two; an empty foil area is set at the tail of the sixth current collector, and the empty foil area is folded in two; the fifth current collector, the third isolation film and the sixth current collector are stacked and wound to obtain a battery cell.

[0172] Comparative Example 3

[0173] The utility model provides a battery cell in comparative example 3, which is generally different from the above-mentioned embodiment 1 in that:

[0174] The battery cell comprises a plurality of first electrode assemblies 1 and second electrode assemblies 2 stacked in sequence;

[0175] The second electrode assembly 2 is disposed on both sides of the first electrode assembly 1 along the second direction.

[0176] The following tests were performed on the batteries of the embodiment and the comparative example, and the test results are shown in Table 1;

[0177] 1) Heavy object impact test

[0178] The battery is fully charged and placed on a plane. A steel column with a diameter of 15.8±0.2mm is placed at the center of the battery with the longitudinal axis of the steel column parallel to the plane. A weight with a mass of 9.1±0.1kg is allowed to fall freely from a height of 610±25mm to the steel column above the battery. 15 batteries obtained from the same embodiment or comparative example are tested in parallel, and the weight impact pass rate of the batteries is calculated.

[0179] 2) Flat plate extrusion test

[0180] Take a fully charged battery, place it between two flat plates, and squeeze it in a direction perpendicular to the plates. Apply a squeezing force of 13.0 kN ± 0.78 kN between the two plates. Stop the squeezing test when the squeezing force reaches the maximum value.

[0181] 3) Screw extrusion test

[0182] Take a fully charged battery and place it between two plates. Place M2*3.5 and M2*4 screws on the surface of the battery and extrude it in a direction perpendicular to the plates. The plate descends at a speed of 900mm / min until the pressure between the two plates reaches 13.0kN±0.78kN. Stop extrusion and maintain the extrusion time for 1s before lifting the extruder.

[0183] 4) Acupuncture test

[0184] Take a fully charged battery and place it on the flat surface. Use a 4mm tungsten steel needle to penetrate the center of the battery at a speed of 200mm / s, hold for 30 minutes, and then slowly lift it up.

[0185] 5) Drop test

[0186] Take a fully charged battery and drop it from a height of 1m onto a hardwood surface three times in the direction most vulnerable to damage (connector end face).

[0187] Table 1

[0188]

[0189] It can be seen from Table 1 that, compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3, the battery of the embodiment of the present invention has a higher mechanical safety test pass rate, including relatively excellent drop performance (the self-discharge rate of the battery remains basically unchanged before and after the drop); significantly improved battery puncture test pass rate and extrusion test pass rate; heavy object impact test pass rate can also be improved to a certain extent.

[0190] Furthermore, it can be seen from Examples 1, 2 and 3 that improvement in the size of the second portion 33 of the second electrode assembly 2 can enhance its current carrying capacity, reduce the transmission impedance of the second electrode assembly 2 when it is short-circuited, enhance the shunt capacity of the second electrode assembly 2, and further improve the safety performance. However, when the size of the second portion 33 reaches a certain level, the safety performance is not significantly improved, and instead the energy density loss of the battery will increase.

[0191] Furthermore, from the safety test results of Example 8 and Comparative Example 3, it can be seen that the second electrode assembly 2 still has a significant improvement effect on the safety of batteries with different structures (ear center structure, multiple ear structure, and laminated structure). It can be seen that the utility model has greatly improved the safety performance of the battery without affecting its electrochemical performance.

[0192] Furthermore, it can be seen from Examples 1 and 14, 15, and 16 that increasing the number of tabs extending from the winding core body can further increase its safety performance. The utility model preferably recommends the use of a solution in which the tabs are extended from the end of the winding core.

[0193] Furthermore, it can be seen from the results of Example 1 and Example 18 that increasing the number of layers of the second electrode assembly 2 can increase the effect of improving safety, and the improvement effect on the impact of heavy objects is most obvious.

[0194] Furthermore, it can be seen from the experimental results of Examples 10 and 11 that this method can reduce the loss of battery energy density while also ensuring the improvement of mechanical safety.

[0195] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

[0196] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0197] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0198] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery cell, comprising a first electrode assembly (1), the first electrode assembly (1) including a first electrode tab, a second electrode tab, and a first separator disposed between the first electrode tab and the second electrode tab, the first electrode tab including a first current collector (11) and a first active material layer disposed on the surface of the first current collector (11), the second electrode tab including a second current collector (12) and a second active material layer disposed on the surface of the second current collector (12); It is characterized in that The battery cell further includes a second electrode assembly (2), the second electrode assembly (2) including a third electrode tab, a fourth electrode tab, and a second separator (23) disposed between the third electrode tab and the fourth electrode tab, the third electrode tab including a third current collector (21) without an active material layer, the fourth electrode tab including a fourth current collector (22) without an active material layer, the second electrode assembly (2) being disposed outside the first electrode assembly (1); The battery cell further includes a first tab and a second tab, the first tab being electrically connected to the first current collector (11) and the third current collector (21) respectively, and the second tab being electrically connected to the second current collector (12) and the fourth current collector (22) respectively.

2. The battery cell according to claim 1, characterized in that: It further includes a tab transfer structure, the tab transfer structure including a tab body (31), a first part (32), and a second part (33); The fixed ends of the tab body (31) are respectively connected to the first part (32) and the second part (33), the first part (32) being electrically connected to the first electrode assembly (1), and the second part (33) being electrically connected to the second electrode assembly (2).

3. The battery cell according to claim 2, characterized in that: Insulating layers are provided on the inner sides of the first part (32) and the second part (33); and / or, the tab body (31) is provided with tab glue (34).

4. The battery cell according to claim 2, characterized in that: In the projection of the battery cell in the second direction, the length of the second part (33) is H1, 5mm < H1 < 100mm; the width is W1, 0 < W1 < 100mm; the thickness is T1, 0 < T1 < 3mm; and / or, the second part (33) and the second electrode assembly (2) are welded to form a welding area, the length of the welding area is H2, H2 ≤ H1; the welding width is W2, W2 ≤ W1.

5. The battery cell according to claim 2, characterized in that: The first current collector (11) and the third current collector (21) are integrally formed into a fifth current collector, the second current collector (12) and the fourth current collector (22) are integrally formed into a sixth current collector, the first separator and the second separator (23) are integrally formed into a third separator, and the fifth current collector, the third separator, and the sixth current collector are laminated and wound to form a wound core.

6. The battery cell according to claim 5, characterized in that: The total number of folds of the wound core is n, the number of the second electrode assemblies (2) is m, and the number of the first tabs is N, 0 < N ≤ n - m; The number of the first tabs is equal to the number of the second tabs.

7. The battery cell according to claim 6, wherein, When N is 1, the first pole tab is located at the innermost head of the winding core; the second pole tab is located at the innermost head of the winding core, the first portion (32) of one pole tab transition structure is connected to the first pole tab, and the first portion (32) of another pole tab transition structure is connected to the second pole tab; Alternatively, when 1≤N<nm, the innermost side of the winding core is the first fold, the first pole lug is located at any position except the first fold, the second pole lug is located at any position except the first fold, the first portion (32) of one pole lug transition structure is connected to the first pole lug, and the first portion (32) of another pole lug transition structure is connected to the second pole lug; Alternatively, when N=nm, the first portion (32) of one of the tab transition structures is connected to a plurality of the first tabs, and the first portion (32) of another of the tab transition structures is connected to a plurality of the second tabs.

8. The battery cell according to claim 2, characterized in that: The first current collector (11) at least partially protrudes along a first direction to form a first region (111), and the second current collector (12) at least partially protrudes along the first direction to form a second region (121); Wherein, the first portion (32) of one of the tab transition structures is integrally arranged with the first region (111), or the first portion (32) of one of the tab transition structures is welded with the first region (111); And / or, the first portion (32) of another of the tab transition structures is integrally arranged with the second region (121), or the first portion (32) of another of the tab transition structures is welded with the second region (121).

9. The battery cell according to claim 2, characterized in that: The battery cell comprises a plurality of first electrode assemblies (1) and second electrode assemblies (2) stacked in sequence; The first electrode tab is electrically connected to a plurality of the first current collectors (11) and the third current collector (21), and the second electrode tab is electrically connected to a plurality of the second current collectors (12) and the fourth current collector (22).

10. The battery cell according to claim 1, characterized in that: The second electrode assembly (2) is at least arranged on two sides of the first electrode assembly (1) along a second direction.

11. The battery cell according to claim 2, characterized in that: Along a first direction, at least a portion of the second electrode assembly (2) is bent and extended to the top of the first electrode assembly (1) to form a protruding area, and the first electrode tab and the second portion (33) of the second electrode tab are both electrically connected to the protruding area.

12. The battery cell according to claim 2, characterized in that: 0 <W1<40mm;0<T1<1mm。 13. An electrochemical device, characterized in that: A battery cell comprising any one of claims 1 to 12.

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