CN111313102A

CN111313102A - Battery cell, electrochemical device comprising same and electronic device

Info

Publication number: CN111313102A
Application number: CN202010139691.9A
Authority: CN
Inventors: 李魁; 安家新
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2020-03-03
Filing date: 2020-03-03
Publication date: 2020-06-19

Abstract

The present application relates to a battery cell, and an electrochemical device and an electronic device including the same. Specifically, the application provides a battery cell, which includes an outer ring of the battery cell with a tab disposed thereon, and in the thickness direction of the battery cell, the tab is disposed opposite to the region of the corresponding pole piece where the active material is disposed. The application provides a battery core has improved security performance.

Description

Battery cell, electrochemical device comprising same and electronic device

Technical Field

The present application relates to a battery cell, and an electrochemical device and an electronic device including the same, and more particularly, to a battery cell having improved safety performance.

Background

At present, electrochemical devices (e.g., lithium ion batteries) are widely used and have been closely related to people's daily life. With the rapid development of intelligent electronic products, the performance requirements of electrochemical devices are higher and higher. However, the safety of the lithium ion battery cannot be effectively guaranteed, and a safety problem caused by the battery being punctured by an external force occasionally occurs at a user end, and even a serious person causes battery explosion. Therefore, with the great popularity of batteries, users, after-sales terminals, and battery manufacturers have made new demands on the safety of batteries. However, the safety problem of the pierced tab has not been solved.

In view of the above, it is necessary to provide a battery cell with improved safety performance.

Disclosure of Invention

Embodiments of the present application seek to solve at least one of the problems in the related art to at least some extent by providing a battery cell and an electrochemical device and an electronic device including the same.

In one aspect of the present application, the present application provides a battery cell comprising a first pole piece and a second pole piece, the first pole piece and the second pole piece being wound to form the battery cell, the first pole piece comprising a first portion and a second portion, the first portion comprising a first current collector, a first active material, and a second active material, wherein: the first current collector includes a first region in which the first active material is disposed, and the second active material is disposed in the first region; the first current collector extends to form the second part along the winding direction of the battery core; the battery cell further comprises a first tab disposed on the second portion; and the second portion is disposed opposite to the first region in a thickness direction of the battery cell.

According to an embodiment of the present application, the first current collector further includes a second region where the first active material is not provided and where the second active material is provided.

According to the embodiment of the application, the battery cell further comprises a second pole lug, the second pole lug is arranged on the second pole piece, and the projections of the first pole lug and the second pole lug in the thickness direction of the battery cell are not overlapped.

According to the embodiment of the application, the first pole lug and the second pole lug are arranged on two sides of a center line along the thickness direction of the battery cell.

According to the embodiment of the application, the first pole lug and the second pole lug are arranged on the same side of the central line of the battery cell in the thickness direction.

According to an embodiment of the present application, the first tab is disposed on a side of the second portion facing the inside of the battery cell.

According to the embodiment of the application, the first tab is arranged on one side of the second portion facing the outside of the battery cell.

According to an embodiment of the present application, the battery cell further includes a separator film present between the first tab and the first region in a winding direction.

According to an embodiment of the present application, the first current collector has a thickness of H1, the first active material has a thickness of H2, the second active material has a thickness of H3, 30 μm H3 100 μm, and 0.5H 1H 2H 3. In some embodiments, 40 μm H3 ≦ 80 μm. In some embodiments, 50 μm H3 ≦ 70 μm. In some embodiments, the thickness H3 of the second active material is 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm. In some embodiments, the thickness H2 of the first active material is 6 μm to 50 μm. In some embodiments, the thickness H2 of the first active material is 10 μm to 40 μm. In some embodiments, the thickness H2 of the first active material is 20 μm to 30 μm. In some embodiments, the thickness H2 of the first active material is 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

According to an embodiment of the present application, the thickness H1 of the first current collector is not greater than 12 μm. In some embodiments, the thickness H1 of the first current collector is no greater than 10 μm. In some embodiments, the thickness H1 of the first current collector is no greater than 5 μm. In some embodiments, the thickness H1 of the first current collector is 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm.

According to an embodiment of the application, at least a part of the first portion is provided with an insulating material.

According to the embodiment of the application, the thickness of the insulating material is H4, and 0.5H1 ≦ H4 ≦ 5H 1. In some embodiments, the thickness H4 of the insulating material is 0.5H1, 1.0H1, 2H1, 3H1, 4H1, or 5H 1.

According to an embodiment of the application, the insulating material is arranged on a side of the first portion opposite to the first active substance.

According to an embodiment of the application, at least a part of the second portion is provided with an insulating material.

According to an embodiment of the present application, the insulating material includes an inorganic compound, a polymer binder, or a combination thereof. In some embodiments, the inorganic compound comprises at least one of alumina, magnesia, silica, zirconia, calcia, or boehmite. In some embodiments, the polymeric binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, styrene butadiene rubber, or polyacrylate.

According to an embodiment of the application, the mohs hardness of the insulating material does not exceed 5. In some embodiments, the insulating material has a mohs hardness of 1, 2, 3, 4, or 5.

According to an embodiment of the application, the insulating material is provided at 5% to 100% of the area of the first portion. In some embodiments, the insulating material is disposed between 10% and 80% of the area of the first portion. In some embodiments, the insulating material is disposed between 20% and 70% of the area of the first portion. In some embodiments, the insulating material is disposed between 30% and 50% of the area of the first portion. In some embodiments, the insulating material is 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100% of the area of the first portion.

According to the embodiment of the application, the thickness of the first current collector is H1, the thickness of the insulating material is H4, and 0.5H1 ≦ H4 ≦ 5H 1. In some embodiments, the thickness H4 of the insulating material is 6 μm to 70 μm. In some embodiments, the thickness H4 of the insulating material is 10 μm to 60 μm. In some embodiments, the thickness H4 of the insulating material is 20 μm to 50 μm. In some embodiments, the thickness H4 of the insulating material is 30 μm to 40 μm. In some embodiments, the thickness H4 of the insulating material is 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 55 μm, or 70 μm.

According to an embodiment of the present application, a side of the second portion opposite to the first tab is provided with an insulating layer.

According to an embodiment of the application, the insulating layer has the same thickness as the insulating material. In some embodiments, the insulating layer has a thickness of 6 μm to 50 μm. In some embodiments, the insulating layer has a thickness of 10 μm to 40 μm. In some embodiments, the insulating layer has a thickness of 20 μm to 30 μm. In some embodiments, the insulating layer has a thickness of 6 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm.

According to the embodiment of this application, the second pole piece includes the second mass flow body, the second mass flow body includes originated straight section and first bend section, originated straight section with first bend section is connected, originated straight section with first bend section with the second pole piece sets up relatively.

According to an embodiment of the present application, the second portion of the first current collector overlaps a projection of the initial straight section of the second current collector in a thickness direction of the cell.

According to an embodiment of the present application, the first active material includes a first binder, the second active material includes a second binder, and a content of the first binder is greater than a content of the second binder.

According to an embodiment of the present application, an ion transfer resistance of the first active material to lithium ions is smaller than an ion transfer resistance of the second active material to lithium ions.

According to an embodiment of the present application, a ratio of the average particle diameter of the second active material to the average particle diameter of the first active material is in a range of 1:1 to 40: 1. In some embodiments, the ratio of the average particle size of the second active material to the average particle size of the first active material is in the range of 5:1 to 30: 1. In some embodiments, the ratio of the average particle size of the second active material to the average particle size of the first active material is in the range of 10:1 to 20: 1. In some embodiments, the ratio of the average particle size of the second active material to the average particle size of the first active material is 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40: 1.

According to an embodiment of the present application, the first active material includes at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium vanadate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium titanate, lithium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, or sodium vanadyl phosphate.

According to an embodiment of the present application, the second active material includes at least one of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, a lithium rich manganese based material, or lithium iron phosphate.

In another aspect of the present application, there is provided an electrochemical device comprising a cell according to the present application.

In yet another aspect of the present application, there is provided an electronic device comprising an electrochemical device according to the present application.

Additional aspects and advantages of embodiments of the present application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the present application.

Drawings

Drawings necessary for describing embodiments of the present application or the prior art will be briefly described below in order to describe the embodiments of the present application. It is to be understood that the drawings in the following description are only some of the embodiments of the present application. It will be apparent to those skilled in the art that other embodiments of the drawings can be obtained from the structures illustrated in these drawings without the need for inventive work.

Fig. 1 is a schematic structural diagram of a battery cell 1 according to the prior art.

Fig. 2 is a schematic structural diagram of a battery cell 2 according to the prior art.

Fig. 3A is a schematic structural diagram of a battery cell 3 according to an embodiment of the present application.

Fig. 3B shows an unfolded structure of a first pole piece 31 of the battery cell 3 of fig. 3A.

Fig. 3C shows an expanded structure of another first pole piece 31 of the battery cell 3 of fig. 3A.

Fig. 3D shows a development structure of yet another first pole piece 31 of the battery cell 3 of fig. 3A.

Fig. 4 is a schematic structural diagram of a battery cell 4 according to an embodiment of the present application.

Fig. 5 is a schematic structural diagram of a battery cell 5 according to an embodiment of the present application.

Fig. 6A is a schematic structural diagram of a battery cell 6 according to an embodiment of the present application.

Fig. 6B shows an unfolded structure of the first pole piece 61 of the battery cell 6 of fig. 6A.

Fig. 7A is a schematic structural diagram of a battery cell 7 according to an embodiment of the present application.

Fig. 7B shows an expanded structure of the first pole piece 71 of the battery cell 7 of fig. 7A.

Fig. 8 is a schematic structural diagram of a battery cell 8 according to an embodiment of the present application.

Fig. 9 is a schematic structural diagram of a battery cell 9 according to an embodiment of the present application.

Fig. 10A shows a schematic diagram of a piercing performed at the end of the first pole piece of the cell.

Fig. 10B shows a schematic diagram of a piercing performed at the ending section of the cell that is not the first pole piece.

Detailed Description

Embodiments of the present application will be described in detail below. In the present specification, the same or similar components and components having the same or similar functions are denoted by like reference numerals. The embodiments described herein with respect to the figures are illustrative in nature, are diagrammatic in nature, and are used to provide a basic understanding of the present application. The embodiments of the present application should not be construed as limiting the present application.

In this application, unless specified or limited otherwise, when a first feature is located "on" or "under" a second feature in a structure, the structure may comprise an embodiment in which the first feature is in direct contact with the second feature, and may comprise another embodiment in which the first feature is not in direct contact with the second feature, but is in contact with an additional feature formed therebetween. Furthermore, when a first feature is located "on," over "or" on top of "a second feature, it can include embodiments in which the first feature is located" on, "over" or "on top" the second feature, directly or obliquely, or merely represents that the height of the first feature is higher than that of the second feature; when a first feature is located "under," under "or" at the bottom of "a second feature, embodiments may be included in which the first feature is located" under, "under" or "at the bottom of" the second feature, either directly or obliquely, or simply represents that the height of the first feature is lower than the height of the second feature.

The most stringent of the tests that are effective in evaluating the safety performance of an electrochemical device (e.g., a lithium ion battery, which is described below as an example) are the nail penetration tests: the lithium ion battery is punctured by a pointed steel nail with a certain diameter at a certain speed, so that the lithium ion battery is short-circuited. The short circuit types can be summarized in two categories: the internal short circuit of the lithium ion battery pole piece, namely the lithium ion battery pole piece contacts and is conducted in the nail piercing process to form a short circuit; and the pole pieces are indirectly short-circuited through the nail, namely the pole pieces of the lithium ion battery are not directly conducted but are all contacted with the nail penetrated by the nail; the nail is made of steel materials and can conduct electricity, so that the pole piece is conducted.

Specifically, the lithium ion battery will have four short circuit modes in the process of nailing: the current collector includes a first active material-a second active material, a first active material-a second current collector, a first current collector-a second current collector, and a first current collector-a second active material. The first pole piece and the second pole piece disclosed by the application are two pole pieces with opposite properties. Therefore, the first active material and the second active material are two corresponding active materials. The first active material may be a positive electrode active material or a negative electrode active material; the second active material may be a negative electrode active material or a positive electrode active material; the first current collector can be a positive current collector or a negative current collector; the second current collector may be a negative electrode current collector or a positive electrode current collector. In some embodiments, the positive electrode current collector may be an aluminum foil or a nickel foil, and the negative electrode current collector may be a copper foil or a nickel foil.

Fig. 1 shows a schematic structural diagram of a battery cell 1 according to the prior art. As shown in fig. 1, in the wound battery cell 1, the first tab 111 and the second tab 121 are located at the inner circle of the battery cell 1, and only one insulating layer 15, one isolating film 13 and one second current collector 122 are arranged between the first tab 111 and the active material 123 of the closest second tab 12.

Fig. 2 shows a schematic structural diagram of a battery cell 2 according to the prior art. The cell 2 differs from the cell 1 in that the end of the first pole piece 21 in the winding direction is provided with an insulating material 24. Similar to the battery cell 1 shown in fig. 1, in the wound battery cell 2, the first tab 211 and the second tab 221 are located at the inner circle of the battery cell 1, and only one insulating layer 15, one isolating film 23 and one second current collector 222 are arranged between the first tab 211 and the active material 223 of the closest second tab 22.

To ensure high energy density, the separator and current collector are typically thin, e.g., the total thickness of the separator and second current collector is typically less than 30 μm. When the first tab (111 in fig. 1 and 211 in fig. 2) is subjected to external force impact or a nail penetration test, burrs or burrs generated from the first tab (111 in fig. 1 and 211 in fig. 2) easily penetrate through the isolation film (13 in fig. 1 and 23 in fig. 2) and the second current collector (122 in fig. 1 and 222 in fig. 2), so that the first current collector (112 in fig. 1 and 212 in fig. 2) is in contact with the active material (123 in fig. 1 and 223 in fig. 2) of the second tab (12 in fig. 1 and 22 in fig. 2) through the burrs or burrs of the first tab (111 in fig. 1 and 211 in fig. 2), causing rapid heat generation of the battery cell and easy risk of combustion and even explosion. Even if two layers of active materials (113 and 114 in fig. 1) are disposed on the first current collector 112 of the battery cell 1 or the insulating material 24 is disposed on the first pole piece 21 of the battery cell 2 at the ending section in the winding direction, the mechanical safety hazard of the battery cell at the pole lug cannot be avoided.

This application is through welding a utmost point ear in order to solve above-mentioned problem at the final phase of the electric core after convoluteing to promote the mechanical security of electric core in utmost point ear position. Specifically, the present application provides a battery cell, the battery cell includes a first pole piece and a second pole piece, the first pole piece and the second pole piece are wound to form the battery cell, the first pole piece includes a first portion and a second portion, the first portion includes a first current collector, a first active material and a second active material, wherein: the first current collector includes a first region in which the first active material is disposed, and the second active material is disposed in the first region; the first current collector extends to form the second part along the winding direction of the battery core; the battery cell further comprises a first tab disposed on the second portion; and the second portion is disposed opposite to the first region in a thickness direction of the battery cell.

The first tab is arranged on the second part of the first pole piece, so that empty foil of the winding initial section of the battery cell can be shortened or eliminated, the probability of contact between the empty foil area of the first pole piece in the battery cell and the second pole piece is reduced, and meanwhile, an insulating layer (such as 15 in fig. 1 and 25 in fig. 2) for protecting the empty foil area of the second pole piece can be removed, so that the safety performance of the battery cell can be improved, the material cost is reduced, and the processing procedures are reduced. When the piercing position is located at the tail end section of the first pole piece of the battery cell (as shown in fig. 10A), the distance between the active materials of the first pole piece and the second pole piece is increased, so that the mechanical safety at the first pole piece can be improved. When the piercing position is located at the non-first pole piece tail section of the battery cell (as shown in fig. 10B), the flash or burr generated by the first pole tab does not contact the active substance of the second pole tab, so that the mechanical safety of the first pole tab can be improved. In addition, the first tab is arranged on the second part of the first pole piece, namely the outer ring of the wound battery cell, so that the number of layers of the isolating film at the initial winding section of the battery cell can be reduced. As shown in fig. 1, the winding start section of the battery cell 1 in the related art has 4 layers of the separator 13. As shown in fig. 3A, the winding start section of the battery cell 3 of the present application has 2 layers of the separator 33, i.e., 2 layers of the separator are reduced compared to the battery cell 1. The reduction of the number of layers of the isolating membrane at the initial section of the battery core is beneficial to improving the energy density of the lithium ion battery. In addition, for the narrow battery cell, the first tab and the second tab are arranged inside the winding battery cell, so that the processing difficulty is increased, the first tab is arranged on the second part of the first tab, the problem is solved, and the processability of the narrow battery cell is improved.

Fig. 3A illustrates a cell structure according to an embodiment of the present application. Fig. 3B shows a schematic expanded structural view of a first pole piece 31 of the battery cell 3 in fig. 3A, where the first pole piece 31 includes a first portion 3101 and a second portion 3102, and the first portion 3101 includes a first current collector 312, a first active material 313 disposed on a surface of the first current collector 312, and a second active material 314 disposed on a surface of the first active material 313. The first portion 3101 in fig. 3B includes a first region including a region a and a region B. In the region a of the first portion 3101, the first active material 313 and the second active material 314 are disposed on both sides of the first current collector 312. In the region b of the first portion 3101, the first active material 313 and the second active material 314 are disposed on one side of the first current collector 312. The first tab 311 is disposed at the second portion 3102. The first pole piece 31 is wound from the first portion 3101 and the second pole piece 32 is wound from the empty foil region where the second pole ear 312 is located. After winding, the second portion 3102 of the first pole piece 31 is disposed opposite the first region. This configuration effectively reduces the chance of the first tab 311 coming into contact with the active material 323 of the second tab 32 when the cell is subjected to an external impact or a nail penetration test at the first tab 311.

Fig. 3C shows a schematic expanded structural view of another first pole piece 31 of the battery cell 3 in fig. 3A, where the first pole piece 31 includes a first portion 3101 and a second portion 3102, and the first portion 3101 includes a first current collector 312, a first active material 313 disposed on a surface of the first current collector 312, and a second active material 314 disposed on a surface of the first active material 313. The first portion 3101 in fig. 3C includes a first region including a region C and a second region including a region d. In the region c of the first portion 3101, the first active material 313 and the second active material 314 are disposed on both sides of the first current collector 312. In the region d of the first portion 3101, only the second active material 314 is provided on the surface of the first current collector 3102. The first tab 311 is disposed at the second portion 3102. The first pole piece 31 is wound from the first portion 3101 and the second pole piece 32 is wound from the empty foil region where the second pole ear 312 is located. After winding, the second portion 3102 of the first pole piece 31 is disposed opposite the first region.

Fig. 3D shows a schematic expanded structural view of another first pole piece 31 of the battery cell 3 in fig. 3A, where the first pole piece 31 includes a first portion 3101 and a second portion 3102, and the first portion 3101 includes a first current collector 312, a first active material 313 disposed on a surface of the first current collector 312, and a second active material 314 disposed on a surface of the first active material 313. The first portion 3101 in fig. 3D includes a first region including a region e and a region g, and a second region including a region f. In the region e of the first portion 3101, the first active material 313 and the second active material 314 are disposed on both sides of the first current collector 312. In the region g of the first portion 3101, the first active material 313 and the second active material 314 are disposed on one side of the first current collector 312. In the region f of the first portion 3101, only the second active material 314 is provided on the surface of the first current collector 3102. The first tab 311 is disposed at the second portion 3102. The first pole piece 31 is wound from the first portion 3101 and the second pole piece 32 is wound from the empty foil region where the second pole ear 312 is located. After winding, the second portion 3102 of the first pole piece 31 is disposed opposite the first region.

According to an embodiment of the present application, the first tab and the second tab may be disposed at both sides of a center line along a thickness direction of the battery cell. As shown in fig. 3A, the first tab 311 and the second tab 321 are disposed on both sides of a center line C in the thickness direction of the battery cell 3.

According to an embodiment of the present application, the first tab and the second tab may be disposed at the same side along a center line of the battery cell in a thickness direction. As shown in fig. 9, the first tab 911 and the second tab 921 are disposed on the same side of the center line C in the thickness direction of the battery cell 9, and the projections of the two tabs in the thickness direction of the battery cell 9 do not overlap.

According to an embodiment of the present application, the first tab may be disposed on a side of the second portion facing an interior of the cell. As shown in fig. 3A, the first tab 311 is located at the second portion of the first pole piece 31, i.e. the tail end in the winding direction, and faces the inside of the wound battery cell.

According to an embodiment of the present application, the first tab may be disposed on a side of the second portion facing an outside of the battery cell. As shown in fig. 4, the first tab 411 is located at the second portion of the first pole piece 41, i.e. the tail end in the winding direction, and faces the outside of the wound battery cell.

According to the embodiment of the application, the battery cell further comprises an isolation film, and the isolation film is arranged between the first tab and the first area along the winding direction. As shown in fig. 5, a separator film 53 is interposed between the first and

second pole pieces

51, 52 and extends to the end of the wound cell, i.e., there is a separator film 53 between the first tab 511 and the first region.

According to an embodiment of the application, at least a part of the first portion is provided with an insulating material. The first pole piece 61 shown in fig. 6A has an expanded configuration as shown in fig. 6B. The first pole piece 61 includes a first portion 6101 and a second portion 6102. The first portion 6101 includes a first current collector 612, a first active material 613 disposed on a surface of the first current collector 612, and a second active material 614 disposed on a surface of the first active material 613. The first portion 6101 includes a first region including a region h and a region i. In the region h of the first portion 6101, the first active material 613 and the second active material 614 are disposed on both sides of the first current collector 612. In the area i of the first portion 6101, the first active material 613 and the second active material 614 are disposed on one side of the first current collector 612, and the insulating material 64 is disposed on the other side of the first current collector 612. The second portion 6102 includes a first empty foil region j and a second empty foil region k. The insulating material 64 extends from area i of the first portion 6101 to the first empty foil area j of the second portion 6102. The first tab 611 is disposed in the second empty foil area k of the second portion 6102. After winding, the second portion 6102 of the first pole piece 61 is disposed opposite the first region.

According to an embodiment of the application, the insulating material is arranged on a side of the first portion opposite to the first active substance. As shown in fig. 6B, in the area i of the first portion 6101, the first active material 613 is disposed on one side of the first current collector 612, and the insulating material 64 is disposed on the other side of the first current collector 612, i.e., opposite to the first active material 613.

According to an embodiment of the application, at least a part of the second portion is provided with an insulating material. As shown in fig. 6B, the second portion 6102 includes a region j and a region k, and an insulating material 64 is disposed in the region j of the second portion 6102.

According to an embodiment of the application, the second portion is provided with an insulating material. Fig. 7B shows an expanded structure diagram of the first pole piece 71 of the battery cell 7 shown in fig. 7A, wherein the first pole piece 71 includes a first portion 7101 and a second portion 7102. The first section 7101 includes regions l and m. In the region m of the first portion 7101, the first active material 713 and the second active material 714 are disposed on one side of the first current collector 712, and the insulating material 74 is disposed on the other side of the first current collector 712. The second section 7102 includes a first empty foil region n and a second empty foil region o. The insulating material 74 extends from the region m of the first section 7101 to the first empty foil region n of the second section 7102. In the second empty foil area o of the second portion 7102, a first tab 711 is disposed on one side of the first current collector 712, and an insulating material 74 is disposed on the other side of the first current collector 712.

According to an embodiment of the application, the mohs hardness of the insulating material does not exceed 5, for example 1, 2, 3, 4 or 5.

According to an embodiment of the present application, a side of the second portion opposite to the first tab is provided with an insulating layer. As shown in fig. 8, an insulating layer 85 is provided between the first tab 811 and the separator 83. In some embodiments, the insulating layer is selected from an insulating glue or a green glue.

According to the embodiment of this application, the second pole piece includes the second mass flow body, the second mass flow body includes originated straight section and first bend section, originated straight section with first bend section is connected, originated straight section with first bend section with the second pole piece sets up relatively. As shown in fig. 9, the second current collector 922 of the second pole piece 92 is connected to the first bent section w along the initial straight section s of the winding direction, and the initial straight section s and the first bent section w are opposite to the second pole piece 32.

According to an embodiment of the present application, the second portion of the first current collector overlaps a projection of the initial straight section of the second current collector in a thickness direction of the cell. As shown in fig. 9, the first current collector 912 of the first pole piece 91 extends along the second portion, i.e., the tail end of the winding direction, to the same side of the perpendicular projection of the first tab 911 and the second tab 912 in the thickness direction of the battery cell 9, so that the projection of the second portion of the first current collector 912 and the initial straight section s of the second pole piece 92 along the winding direction in the thickness direction of the battery cell overlap.

According to an embodiment of the present application, the first active material includes a first binder, the second active material includes a second binder, and a content of the first binder is greater than a content of the second binder. In some embodiments, the weight ratio of the first binder to the second binder is 1.1 to 4, e.g., 1.1, 1.5, 2.5, 3, 3.5, or 4. In some embodiments, the second binder is present in an amount of 0.1 to 5 weight percent, e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, based on the total weight of the first pole piece. In some embodiments, the first binder and the second binder are each selected from at least one of polyvinylidene fluoride, copolymers of vinylidene fluoride-fluorinated olefins, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene butadiene rubber, polyurethane, fluorinated rubber, or polyvinyl alcohol. In some embodiments, the first binder and the second binder are the same or different.

According to an embodiment of the present application, an ion transfer resistance of the first active material to lithium ions is smaller than an ion transfer resistance of the second active material to lithium ions. In some embodiments, the first active material comprises a first metal oxide and the second active material comprises a second metal oxide, the first metal oxide and the second metal oxide being the same or different. In some embodiments, the first metal oxide is selected from zirconia and the second metal oxide is selected from at least one of alumina, magnesia, zinc oxide, or manganese dioxide. In some embodiments, the first metal oxide and the second metal oxide are the same, and the content of the first metal oxide is less than the content of the second metal oxide. In some embodiments, the first metal oxide is present in an amount of 0.01 wt% to 5 wt%, for example, 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%, based on the total weight of the first pole piece. In some embodiments, the second metal oxide is present in an amount of 0.01 wt% to 10 wt%, e.g., 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, or 9.5 wt%, 10 wt%.

According to an embodiment of the application, the ratio of the average particle size of the second active substance to the average particle size of the first active substance is in the range of 1:1 to 40:1, e.g. 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1 or 40: 1. In some embodiments, the first active material has an average particle size in a range of 0.2 μm to 15 μm, for example, 0.2 μm, 0.5 μm, 0.8 μm, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 12 μm, or 15 μm. In some embodiments, the particle size of the first active material that accumulates 90% by volume is 40 μm or less, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or 40 μm.

The electrochemical device of the present application includes any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The use of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the art. In one embodiment, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.

Taking a lithium ion battery as an example and describing the preparation of the lithium ion battery with reference to specific examples, those skilled in the art will understand that the preparation method described in the present application is only an example, and any other suitable preparation method is within the scope of the present application.

Examples

1. Preparation method of lithium ion battery

Preparation of the Positive electrode

Dissolving lithium iron phosphate, polyvinylidene fluoride and conductive carbon black in N-methyl pyrrolidone according to the weight ratio of 92.6:6:1.4, and uniformly stirring to obtain first active material slurry. The first active material slurry was coated on both sides of a 10 μm aluminum foil and dried at 85 ℃. And dissolving lithium cobaltate, a binder and a conductive agent in N-methyl pyrrolidone according to the weight ratio of 96:2:2, and uniformly stirring to obtain second active material slurry. The second active material slurry was coated on both sides of the above aluminum foil coated with the first active material slurry. And drying, cold pressing and splitting to obtain the anode.

Preparation of the negative electrode

Graphite, sodium carboxymethylcellulose (CMC) and styrene butadiene rubber are dissolved in deionized water according to the weight ratio of 97.5:1.5:1 to prepare negative electrode slurry. And uniformly coating the negative electrode slurry on two sides of a copper foil with the thickness of 6 microns, drying at 85 ℃, and then cold-pressing and splitting to obtain the negative electrode.

Preparation of insulating materials

Dissolving aluminum oxide and polyvinylidene fluoride in a weight ratio of 80:20 in N-methyl pyrrolidone, and uniformly stirring to obtain the insulating material slurry. An insulating material slurry was applied to the surface of the pole piece according to the setup of the example.

Preparation of the separator

An 8 μm polyethylene film was used as the separator.

Preparation of the electrolyte

Uniformly mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) according to a weight ratio of 30:30:40 to obtain the non-aqueous solvent. Mixing LiPF₆And uniformly mixing the electrolyte with a nonaqueous organic solvent according to the weight ratio of 8:92 to obtain the electrolyte.

Preparation of lithium ion battery

And sequentially laminating the positive electrode, the isolating film and the negative electrode, and winding to obtain the bare cell. And (3) placing the wound bare cell into an aluminum-plastic touch packaging bag, injecting electrolyte, packaging, forming, and performing air exhaust forming to prepare the lithium ion battery.

The cell structures used in the examples and comparative examples of the present application are explained below. In each of the following cell structures, the first electrode sheet is a positive electrode, and the second electrode sheet is a negative electrode. In an alternative embodiment, the first pole piece can also be a negative pole, and the second pole piece can also be a positive pole.

Battery cell 1

As shown in fig. 1, the battery cell 1 includes a first pole piece 11, a second pole piece 12, and a separation film 13 disposed between the first pole piece 11 and the second pole piece 12, where the first pole piece 11 includes a first current collector 112, a first active material 113 disposed on a surface of the first current collector 112, and a second active material 114 disposed on a surface of the first active material 113, the second pole piece 12 includes a second current collector 122 and an active material 123 disposed on a surface of the second current collector 122, a first tab 111 is disposed on a surface of the first current collector 112 of the first pole piece 11, an insulating layer 15 is disposed on a surface of the first tab 111, and a second tab 121 is disposed on a surface of the second current collector 122 of the second pole piece 12. After winding, the first tab 111 and the second tab 121 are located at the inner circle of the battery cell 1. Only one insulating layer 15, one isolating film 13 and one second current collector 122 are arranged between the first tab 111 and the active material 123 of the nearest second pole piece 12.

Battery cell 2

As shown in fig. 2, the battery cell 2 includes a first pole piece 21, a second pole piece 22, and a separation film 23 disposed between the first pole piece 21 and the second pole piece 22, the first pole piece 21 has a first current collector 212, a first active material 213 disposed on a surface of the first current collector 212, and a second active material 214 disposed on a surface of the first active material 213, the second pole piece 22 includes a second current collector 222 and an active material 223 disposed on a surface of the second current collector 222, the first tab 211 is disposed on a surface of the first current collector 212 of the first pole piece 21, the insulation layer 25 is disposed on a surface of the first tab 211, and the second tab 221 is disposed on a surface of the second current collector 222 of the second pole piece 22. The battery cell 2 differs from the battery cell 1 in that, in the winding direction, the first current collector 212, which is not provided with the first active material 213 or the second active material 214 at the tail end of the first pole piece 21 of the battery cell 2, contains the insulating material 24. Similar to the battery cell 1 shown in fig. 1, after winding, the first tab 211 and the second tab 221 are located at the inner circle of the battery cell 1. Only one insulating layer 25, one isolating film 23 and one second current collector 222 are arranged between the first tab 211 and the active material 223 of the nearest second tab 22.

Battery cell 3

As shown in fig. 3A, the battery cell 3 includes a first pole piece 31, a second pole piece 32, and a separation film 33 disposed between the first pole piece 31 and the second pole piece 32, the first pole piece 31 includes a first current collector 312, a first active material 313 disposed on a surface of the first current collector 312, and a second active material 314 disposed on a surface of the first active material 313, the second pole piece 32 includes a second current collector 322 and an active material 323 disposed on a surface of the second current collector 322, the first tab 311 is disposed on a surface of the first current collector 212 of the first pole piece 21, and the second tab 321 is disposed on a surface of the second current collector 222 of the second pole piece 22. The first pole piece 31 of the battery cell 3 has an expanded structure as shown in fig. 3B, wherein the first pole piece 31 includes a first portion 3101 and a second portion 3102. The first portion 3101 includes a first region including a region a and a region b. In the region a of the first portion 3101, the first active material 313 and the second active material 314 are disposed on both sides of the first current collector 312. In the region b of the first portion 3101, the first active material 313 and the second active material 314 are disposed on the first current collector 312 side. The first tab 311 is disposed at the second portion 3102. The first pole piece 31 is wound from the first portion 3101 and the second pole piece 32 is wound from the empty foil region where the second pole ear 312 is located. After winding, the first tab 311 is located at the outer ring of the battery cell and faces the inside of the battery cell, and the second tab 321 is located at the inner ring of the battery cell. The first tab 311 and the active material 323 of the nearest second tab 32 are separated by a layer of first current collector 312, a layer of first active material 313, a layer of second active material 314, and a layer of separator 33.

Battery cell 4

As shown in fig. 4, the battery cell 4 includes a first pole piece 41, a second pole piece 42, and a separation film 43 disposed between the first pole piece 41 and the second pole piece 42, where the first pole piece 41 includes a first current collector 412, a first active material 413 disposed on a surface of the first current collector 412, and a second active material 414 disposed on a surface of the first active material 413, the second pole piece 42 includes a second current collector 422 and an active material 423 disposed on a surface of the second current collector 422, the first tab 411 is disposed on a surface of the first current collector 412 of the first pole piece 41, and the second tab 421 is disposed on a surface of the second current collector 422 of the second pole piece 42. The first pole piece 41 has the same structure as shown in fig. 3B. One of the differences between the battery cell 4 and the battery cell 3 is that the first tab 411 in the battery cell 4 is located at the outer ring of the battery cell and faces the outside of the battery cell. Two layers of first current collectors 412, one layer of first active material 413, one layer of second active material 414 and one layer of isolating film 43 are arranged between the first tab 411 and the active material 423 of the nearest second pole piece 42.

Battery cell 5

As shown in fig. 5, the battery cell 5 includes a first pole piece 51, a second pole piece 52, and a separation film 53 disposed between the first pole piece 51 and the second pole piece 52, where the first pole piece 51 includes a first current collector 512, a first active material 513 disposed on a surface of the first current collector 512, and a second active material 514 disposed on the first active material 513, the second pole piece 52 includes a second current collector 522 and an active material 523 disposed on a surface of the second current collector 522, a first tab 511 is disposed on the surface of the first current collector 512 of the first pole piece 51, and a second tab 521 is disposed on the surface of the second current collector 522 of the second pole piece 52. The first pole piece 51 has the same structure as shown in fig. 3B. One of the differences between the battery cell 5 and the battery cell 4 is that the separator 53 in the battery cell 5 extends between the first tab 511 and the active material 523 of the nearest second tab 52. The first tab 511 is separated from the active material 523 of the nearest second tab 52 by two layers of a first current collector 512, one layer of a first active material 513, one layer of a second active material 514, and three layers of a separator 53.

Battery cell 6

As shown in fig. 6A, the battery cell 6 includes a first pole piece 61, a second pole piece 62, and a separation film 63 disposed between the first pole piece 61 and the second pole piece 62, the first pole piece 61 includes a first current collector 612, a first active material 613 disposed on a surface of the first current collector 612, and a second active material 614 disposed on a surface of the first active material 613, the second pole piece 62 includes a second current collector 622 and an active material 623 disposed on a surface of the second current collector 622, the first tab 611 is disposed on a surface of the first current collector 612 of the first pole piece 61, and the second tab 621 is disposed on a surface of the second current collector 622 of the second pole piece 62. The first pole piece 61 of the battery cell 6 has an expanded structure as shown in fig. 6B, in which the first pole piece 61 includes a first portion 6101 and a second portion 6102. The first portion 6101 includes a first region including a region h and a region i. In the region h of the first portion 6101, the first active material 613 and the second active material 614 are disposed on both sides of the first current collector 612. In the area i of the first portion 6101, the first active material 613 and the second active material 614 are disposed on one side of the first current collector 612, and the insulating material 64 is disposed on the other side of the first current collector 612. The second portion 6102 includes a first empty foil region j and a second empty foil region k. The insulating material 64 extends from area i of the first portion 6101 to the first empty foil area j of the second portion 6102. The first tab 611 is disposed in the second empty foil area k of the second portion 6102. The first pole piece 61 is wound from the first portion 6101 and the second pole piece 62 is wound from the empty foil region where the second pole ear 612 is located. After winding, the first tab 611 is located at the outer ring of the cell and faces the outside of the cell, and the second tab 621 is located at the inner ring of the cell. One of the differences between the cell 6 and the cell 5 is that the end of the first pole piece 61 of the cell 6 includes an insulating material 64. The first tab 611 is separated from the active material 623 of the nearest second tab 62 by a layer of a first current collector 612, a layer of a first active material 613, a layer of a second active material 614, a three-layer separator 33, and a layer of insulating material 64.

Battery cell 7

As shown in fig. 7A, the battery cell 7 includes a first pole piece 71, a second pole piece 72, and a separation film 73 disposed between the first pole piece 71 and the second pole piece 72, the first pole piece 71 includes a first current collector 712, a first active material 713 disposed on a surface of the first current collector 712, and a second active material 714 disposed on a surface of the first active material 713, the second pole piece 72 includes a second current collector 722 and an active material 723 disposed on a surface of the second current collector 722, the first tab 711 is disposed on the surface of the first current collector 712 of the first pole piece 71, and the second tab 721 is disposed on the surface of the second current collector 722 of the second pole piece 72. The battery cell 7 has an expanded structure schematic diagram of a first pole piece 71 shown in fig. 7B, where the first pole piece includes a first portion 7101 and a second portion 7102. The first section 7101 includes a first region including region i and region m. In a region l of the first portion 7101, the first active material 713 and the second active material 714 are disposed on both sides of the first current collector 712. In the region m of the first portion 6101, the first active material 713 and the second active material 714 are disposed on one side of the first current collector 712, and the insulating material 74 is disposed on the other side of the first current collector 712. The second section 7102 includes a first empty foil region n and a second empty foil region o. The insulating material 74 extends from the region m of the first section 7101 to the first empty foil region n of the second section 7102. In the second empty foil area o of the second portion 7102, a first tab 711 is disposed on one side of the first current collector 712, and an insulating material 74 is disposed on the other side of the first current collector 712. After winding, the second portion 7102 is positioned opposite the first region. The first pole piece 71 is wound from the first section 7101 and the second pole piece 72 is wound from the empty foil area of the second pole ear 712. After winding, the first tab 711 is located at the outer ring of the battery cell and faces the outside of the battery cell, and the second tab 721 is located at the inner ring of the battery cell. One of the differences between cell 7 and cell 6 is that the insulating material 74 is disposed on the side of the first current collector 712 opposite the first tab 711. A first current collector 712, a first active material 713, a second active material 714, a three-layer isolating film 73 and two layers of insulating materials 74 are arranged between the first tab 711 and the active material 723 of the nearest second pole piece 72.

Battery cell 8

As shown in fig. 8, the battery cell 8 includes a first pole piece 81, a second pole piece 82, and a separation film 83 disposed between the first pole piece 81 and the second pole piece 82, the first pole piece 81 has a first current collector 812, a first active material 813 disposed on a surface of the first current collector 812, and a second active material 814 disposed on a surface of the first active material 813, the second pole piece 82 has a second current collector 822 and an active material 823 disposed on a surface of the second current collector 822, a first tab 811 is disposed on a surface of the first current collector 812 of the first pole piece 81, and a second tab 821 is disposed on a surface of the second current collector 822 of the second pole piece 82. The first pole piece 81 has the same structure as shown in fig. 7B. One of the differences between the battery cell 8 and the battery cell 7 is that an insulating layer 85 is further disposed between the first tab 811 and the active material 823 of the closest second tab 82, the insulating layer 85 is disposed on the surface of the insulating material 84 opposite to the first tab 811, and the projection of the insulating layer 85 in the vertical direction is larger than the projection of the first tab 811 in the vertical direction. The first tab 811 is separated from the active material 823 of the nearest second tab 82 by a first current collector 812, a first active material 813, a second active material 814, a three-layer separator 73, two layers of insulating material 84, and an insulating layer 85.

Battery cell 9

As shown in fig. 9, the battery cell 9 includes a first pole piece 91, a second pole piece 92, and a separation film 93 disposed between the first pole piece 91 and the second pole piece 92, the first pole piece 91 includes a first current collector 912, a first active material 913 disposed on a surface of the first current collector 912, and a second active material 914 disposed on a surface of the first active material 913, the second pole piece 92 includes a second current collector 922 and an active material 923 disposed on a surface of the second current collector 922, the first tab 911 is disposed on a surface of the first current collector 912 of the first pole piece 91, and the second tab 921 is disposed on a surface of the second current collector 922 of the second pole piece 92. The first pole piece 91 has the same structure as shown in fig. 7B. One of the differences between the battery cell 9 and the battery cell 8 is that the first tab 911 and the second tab 921 are located on the same side of the battery cell 9 in the thickness direction (i.e., the center line C), and the second portion of the first current collector 912 overlaps with the projection of the initial straight section s of the second tab 92 in the winding direction in the thickness direction of the battery cell, but the projections of the first tab 911 and the second tab 912 in the thickness direction of the battery cell do not overlap. A first current collector 912, a first active material 913, a second active material 914, three layers of separators 93, two layers of insulating materials 94 and an insulating layer 95 are interposed between the first tab 911 and the active material 923 of the nearest second electrode sheet 92.

2. Method for testing safety of lithium ion battery

And (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. The lithium ion battery reaching the constant temperature is charged at a constant current of 0.5C until the cut-off voltage is 4.45V, and then the lithium ion battery is charged at a constant voltage until the current is 0.02C. And transferring the fully charged lithium ion battery to a nail penetration testing machine, keeping the ambient temperature at 25 +/-3 ℃, and uniformly penetrating the position of a first tab of the battery cell by using a steel nail with the diameter of 4mm at a speed of 30mm/s for 5 minutes. Taking the embodiment of the present application as an example, the position of the nail passing through the first pole piece from the trailing surface is shown in fig. 10A, and the position of the nail passing through the first pole piece from the non-trailing surface is shown in fig. 10B. After the test was completed, the lithium ion battery was observed and recorded as passing with no smoke, no fire and no explosion. 20 samples were tested per example or comparative example and the nail penetration test pass rate was calculated by the following formula:

the nail penetration test pass rate (number of samples passed the nail penetration test/total number of samples tested) x 100%.

3. Test results

The following table shows the cell structures used in the examples and comparative examples of the present application and their mechanical safety at the tabs.

As shown in comparative examples 1 to 5, the mechanical safety at the tab was poor with the cell structure of the prior art. As shown in examples 1 to 10, with the cell structure of the present application, a distance between the first tab and the active material of the closest second pole piece may be increased, so that mechanical safety of the cell at the tab may be significantly improved. The greater the distance between the first pole lug and the active material of the second pole piece closest to the first pole lug, the higher the safety of the battery cell at the pole lug.

As shown in

embodiments

1 and 2, with the

cell structure

3 or 4 of the present application (i.e., one tab is located at the outer ring of the cell, and the other tab is located at the inner ring of the cell), the mechanical safety at the tab is significantly improved. The first tab of the cell structure 3 in embodiment 1 is located in the outer ring of the cell and faces the inside of the cell, and the first tab of the cell structure 4 in embodiment 2 is located in the outer ring of the cell and faces the outside of the cell. According to the above result, the mechanical safety of the tab position can be further improved by making the tab of the outer ring of the battery cell face the outside of the battery cell than the inside of the battery cell, because compared with the tab of the outer ring of the battery cell facing the inside of the battery cell, when the tab of the outer ring of the battery cell faces the outside of the battery cell, the first tab and the active material of the closest second pole piece are additionally separated by the first current collector.

As shown in examples 2 to 4, increasing the thickness of the first active material and/or the second active material of the first pole piece can further improve the mechanical safety at the tab.

As shown in examples 4 and 5, the mechanical safety of the tab can be further improved by extending the length of the separator at the end of the wound cell.

As shown in examples 6 and 7, the provision of the insulating material on the cell structure can further improve the mechanical safety at the tab. The greater the thickness of the insulating material, the higher the mechanical safety at the tab.

As shown in examples 7 and 8, additionally providing an insulating material at the first tab may further improve mechanical safety at the tab.

As shown in examples 8 and 9, the additional provision of an insulating layer at the first tab can further improve the mechanical safety at the tab.

As shown in example 10, when the first tab and the second tab are disposed on the same side of the center line of the cell structure in the thickness direction, but the projections of the first tab and the second tab in the thickness direction do not overlap, the same safety performance as that when the first tab and the second tab are disposed on both sides of the center line of the cell structure in the thickness direction can be achieved.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment," "another example," "an example," "a specific example," or "some examples" means that at least one embodiment or example in this application includes a particular feature, structure, material, or characteristic described in the embodiment or example. Thus, throughout the specification, descriptions appear, for example: "in some embodiments," "in an embodiment," "in one embodiment," "in another example," "in one example," "in a particular example," or "by example," which do not necessarily refer to the same embodiment or example in this application. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims

1. A cell comprising a first pole piece and a second pole piece wound to form the cell, the first pole piece comprising a first portion comprising a first current collector, a first active material, and a second active material, wherein:

the first current collector includes a first region in which the first active material is disposed, and the second active material is disposed in the first region;

the first current collector extends to form the second part along the winding direction of the battery core;

the battery cell further comprises a first tab disposed on the second portion; and

the second portion is disposed opposite to the first region in a thickness direction of the battery cell.

2. The electrical core of claim 1, the first current collector further comprising a second region where the first active species is not disposed and where the second active species is disposed.

3. The cell of claim 1, further comprising a second tab disposed on the second pole piece, wherein projections of the first tab and the second tab in a thickness direction of the cell do not overlap.

4. The cell of claim 3, wherein the first and second tabs are disposed on either side of a center line along a thickness direction of the cell.

5. The cell of claim 1, wherein the first tab is disposed on a side of the second portion facing an interior of the cell or the first tab is disposed on a side of the second portion facing an exterior of the cell.

6. The cell of claim 1, further comprising a separator film present between the first tab and the first region in a winding direction.

7. The battery cell of claim 1, wherein the first current collector has a thickness of H1, the first active material has a thickness of H2, the second active material has a thickness of H3, 30 μm H3 100 μm, and 0.5H 1H 2 0.5H 3.

8. The electrical core of claim 1, wherein at least a portion of the first portion is provided with an insulating material.

9. The electrical core of claim 8, wherein the insulating material is disposed on a side of the first portion opposite the first active material.

10. The electrical core of claim 8, wherein at least a portion of the second portion is provided with an insulating material.

11. The electrical core of claim 8, wherein the insulating material is disposed between 5% and 100% of the area of the first portion.

12. The cell of claim 8, wherein the first current collector has a thickness of H1, the insulating material has a thickness of H4, and 0.5H1 ≦ H4 ≦ 5H 1.

13. The cell of claim 8, wherein a side of the second portion opposite the first tab is provided with an insulating layer.

14. The electrical core of claim 13, wherein the insulating layer has the same thickness as the insulating material.

15. The cell of claim 1, wherein the second pole piece comprises a second current collector comprising a starting straight section and a first bent section, the starting straight section being connected to the first bent section, the starting straight section and the first bent section being disposed opposite the second pole piece.

16. The cell of claim 15, wherein the second portion of the first current collector overlaps a projection of the initial straight section of the second current collector in a thickness direction of the cell.

17. An electrochemical device comprising the cell of any of claims 1-16.

18. An electronic device comprising the electrochemical device of claim 17.