CN214589166U

CN214589166U - Utmost point ear, pole piece and lithium ion battery

Info

Publication number: CN214589166U
Application number: CN202120821170.1U
Authority: CN
Inventors: 张保海; 彭冲; 李俊义
Original assignee: Zhuhai Cosmx Battery Co Ltd
Current assignee: Zhuhai Cosmx Battery Co Ltd
Priority date: 2021-04-20
Filing date: 2021-04-20
Publication date: 2021-11-02
Anticipated expiration: 2031-04-20

Abstract

The utility model provides a utmost point ear, pole piece and lithium ion battery. Wherein, the utility model provides a pair of pole piece, include: mass flow body, active substance layer and utmost point ear, the active substance layer sets up the positive and negative two surfaces of mass flow body and/or on one of them is surperficial in the positive and negative two surfaces of mass flow body, at least one end of mass flow body length direction is left and is not set up the empty foil district on the active substance layer, utmost point ear sets up mass flow body length direction one end empty foil district is last, utmost point ear include first section and with the second section that first section is connected, the both sides of first section top surface all have undercut's concave part. The utility model provides a utmost point ear, pole piece and lithium ion battery for solve the pole piece at least and process into lithium ion battery, because the pole piece that the utmost point ear structure arouses processes into the unsatisfactory technical problem of roughness on electric core surface.

Description

Utmost point ear, pole piece and lithium ion battery

Technical Field

The utility model relates to a lithium ion battery field especially relates to a utmost point ear, pole piece and lithium ion battery.

Background

At present, with the strong support of the country on new energy, lithium ion batteries are rapidly developed as green and environment-friendly new energy, and have been widely applied to the fields of digital products, electric automobiles and military products, people put higher requirements on energy density, quick charging capacity and charging and discharging multiplying power of lithium ion batteries, and quick-charging lithium batteries are also the development trend of consumer lithium ion batteries.

The formation is an extremely important process in the manufacturing process of the lithium ion battery, is an important link for ensuring the service life of the battery, and plays an important role in the performance of the battery. Whether the pressure born in the formation process of the lithium ion battery is uniform or not influences the interface bonding performance of the lithium ion battery, and whether the interface bonding of the lithium ion battery is good or not can obviously influence the long cycle life of the lithium ion battery during high-rate charging, and also can cause the expansion phenomenon of the lithium ion battery in the cyclic charging and discharging process and even cause the deformation of the lithium ion battery in the use process.

The key of whether the pressure borne in the formation process of the lithium ion battery is uniform lies in whether the flatness of the whole battery cell is good, the smaller the difference between the highest point and the lowest point on the surface of the battery cell is, the better the flatness of the battery cell is, and in the formation process, the poor flatness of the battery cell can cause uneven pressure borne by a pole piece, so that the problems of uneven surface, depression, wave deformation and the like of the battery cell are finally caused. In the long circulation process, the flatness of the battery core is not ideal, so that the stress borne by the battery core in the circulation expansion process is not uniform, and finally, the battery core is expanded and deformed to cause the problems of capacity attenuation, expansion failure and the like. Therefore, there is an urgent need for improvement of a tab, a pole piece and a lithium ion battery structure, so that when the pole piece is processed into a battery cell, the flatness of the surface of the battery cell caused by the tab structure can be improved, and the service life of lithium ions can be ensured.

SUMMERY OF THE UTILITY MODEL

The utility model provides a utmost point ear, pole piece and lithium ion battery for solve at least that current pole piece is processed into the unsatisfactory technical problem of roughness on electric core surface that causes because utmost point ear structure in the lithium ion battery.

In order to achieve the above object, the present invention provides a tab, the tab includes a first section and a second section connected to the first section, both sides of the top surface of the first section all have a concave portion recessed downward.

The utility model provides a pair of in utmost point ear, the both sides of the top surface of first section all have undercut's concave part, the concave part is used for holding the insulated adhesive paper to when avoiding processing into the pole piece the insulated adhesive paper is higher than the top surface of first section arouses the difference of pole piece surface altitude variation is great, leads to the thickness of pole piece is uneven.

In one possible embodiment, the recess penetrates through both ends of the first segment in the length direction, and the width L1 of the recess is 10mm to 15 mm;

a distance H1 is arranged between the bottom surface of the concave part and the top surface of the first section, and the value of the distance H1 is in the range of 15-25 μm; and/or the presence of a gas in the gas,

the width of the first section is greater than the width of the second section.

In a possible implementation mode, the two sides of the first section are also provided with steps positioned at the bottom of the concave part, the edge of the upper end of each step is in a circular arc shape, and the radius R of the circular arc shape is 1/3 times of the thickness of the first section; or

The radius R of the circular arc is 1/6 times the thickness of the first segment.

The utility model provides a still another pole piece, include: mass flow body, active substance layer and foretell utmost point ear, the active substance layer sets up the body of collection positive and negative two surfaces and/or on one of them surface in the positive and negative two surfaces of mass flow body, at least one end of mass flow body length direction is left and is not set up the empty foil district on the active substance layer, utmost point ear sets up mass flow body length direction one end empty foil is distinguished, utmost point ear include first section and with the second section that first section is connected, the both sides of the top surface of first section all have undercut's concave part.

The utility model provides a pair of in pole piece, the both sides of the top surface of first section all have undercut's concave part, the concave part is used for holding the insulated adhesive paper, thereby avoids the insulated adhesive paper is higher than the top surface of first section arouses the difference of pole piece surface altitude is great, leads to the thickness of pole piece is uneven. Therefore, after the pole piece is wound into the battery cell, the smoothness of the surface of the battery cell caused by the structure of the pole lug is improved, the uniform thickness distribution of the surface of the battery cell is facilitated, the problems of uneven surface, depression, wave deformation and the like of the battery cell caused by uneven stress of the pole piece during formation are solved, and the condition of cyclic expansion failure of the battery cell is improved.

In one possible embodiment, the hollow foil area is rectangular, a side surface of the first section close to the active material layer in the width direction of the first section is a limiting surface, and a distance H2 is provided between an end surface of the active material layer close to the limiting surface and the limiting surface.

In a possible implementation manner, the first section extends along a width direction of the current collector, and a length of the first section is 40% to 105% of the width of the current collector.

The structure enables the thickness distribution of the pole piece to tend to be uniform along the width direction of the current collector, and is beneficial to improving the flatness of the pole piece after being processed into the battery core.

In a possible embodiment, the thickness of the second section is equal to the thickness of the first section, the thickness h of the first section having a value ranging from: h is more than or equal to 45 mu m and less than or equal to 115 mu m.

In one possible embodiment, the pole piece further includes an insulating adhesive paper, and the insulating adhesive paper covers at least the recesses of the tabs and at least a part of the empty foil areas of the pole piece.

The utility model also provides a lithium ion battery, including electric core, electric core includes negative electrode piece, positive electrode piece and the interval negative electrode piece with the diaphragm of positive electrode piece, negative electrode piece with the positive electrode piece is the above-mentioned pole piece, negative electrode piece, positive electrode piece and the diaphragm is coiled after the lamination and is constituted electric core, electric core has a plurality of circle layers that coil outward in proper order and set up;

and the lug on the negative electrode plate is positioned on the inner ring layer of the battery cell, or the lug on the negative electrode plate is positioned on the outer ring layer of the battery cell.

The utility model provides a pair of lithium ion battery, through adopting foretell pole piece and utmost point ear, the thickness spatial adjustment electric core self roughness that modified utmost point ear and pole piece structure can make full use of electricity core self, and does not increase electric core self thickness, does not influence electric core energy density, reaches the purpose that roughness and energy degree were compromise.

In a possible implementation manner, one side surface of the first section of the tab, which is close to the active material layer of the pole piece, is a limiting surface, and a distance H2 is formed between one end surface of the active material layer, which is close to the limiting surface, and the limiting surface; the separation H2 is greater than 2 times the thickness H of the first segment, and the difference between the separation H2 and 2 times the thickness H of the first segment is δ 1, the value of δ 1 ranging from: delta 1 is more than or equal to 2mm and less than or equal to 10 mm; and/or

The distance H2 is greater than pi/2 times the thickness T of the cell, and the difference between the distance H2 and pi/2 times the thickness T of the cell is δ 2, where the numerical range of δ 2 is: delta 2 is more than or equal to 1mm and less than or equal to 5mm or delta 2 is more than or equal to 1mm and less than or equal to 4 mm.

In one possible implementation manner, when the tab on the negative electrode sheet and/or the tab on the positive electrode sheet are located on the inner ring layer of the cell, the width D of the tab on the negative electrode sheet and/or the tab on the positive electrode sheet satisfies:

the inner width L2-the distance H2-1mm of the battery cell is more than or equal to D and is more than or equal to the inner width L2-the distance H2-5mm of the battery cell;

the inner width L2 of the battery cell is the width of the innermost ring layer of the battery cell in the orthographic projection direction of the battery cell.

In one possible implementation manner, when the tab on the negative electrode sheet and/or the tab on the positive electrode sheet are located on the outer ring layer of the cell, the width D of the tab on the negative electrode sheet and/or the tab on the positive electrode sheet satisfies:

the external width L3-the thickness T-1mm of the battery cell is more than or equal to D and is more than or equal to the external width L3-the thickness T-5mm of the battery cell;

the outer width L3 of the battery cell is the width of the outer ring layer of the battery cell in the orthographic projection direction of the battery cell, and the thickness T of the battery cell is the height of the outer ring layer of the battery cell in the lateral projection direction of the battery cell.

In a possible implementation manner, when the tab on the negative electrode sheet and/or the tab on the positive electrode sheet are located on the inner ring layer of the battery cell, the edge of the upper end of the step of the tab is arc-shaped, and the radius R of the arc-shaped is 1/6 times of the thickness of the first section; or

When the lug on the negative electrode plate and/or the lug on the positive electrode plate are/is located on the outer ring layer of the battery cell, the edge of the upper end of the step of the lug is arc-shaped, and the radius R of the arc-shaped is 1/3 times of the thickness of the first section.

In the lug, the pole piece and the lithium ion battery provided by the utility model, the structure of the lug and the pole piece is improved, so that the thickness distribution of the innermost layer of the battery cell can be effectively improved, and the problems of uneven surface, depression, wave deformation and the like of the shipment battery cell caused by uneven stress of the pole piece during formation are improved; the uniform formation pressure can also effectively improve the problem of poor bonding of the diaphragm; the problem of lithium precipitation caused by poor adhesion between the pole piece and the diaphragm in the later stage of cyclic charge and discharge is solved; the flatness of the battery cell is improved; and the condition of cyclic expansion failure is changed.

Improved pole piece structure can make full use of the thickness spatial adjustment electric core self roughness of electric core self in this application, and does not increase electric core self thickness, does not influence electric core energy density, reaches the purpose that roughness and energy degree were compromise. The problems of failure of a bonding section of the battery core, expansion deformation of the battery core, capacity attenuation and expansion failure caused by the nonuniform internal stress of the pole piece of the battery core in the cyclic expansion process caused by the flatness problem of the battery core in the long cycle process can be effectively improved, and the cycle life and the safety performance of the battery are improved.

In addition to the technical problems solved by the embodiments of the present invention, the technical features constituting the technical solutions, and the advantageous effects brought by the technical features of these technical solutions, the embodiments of the present invention provide a tab, a pole piece, and a lithium ion battery, which can solve other technical problems, other technical features included in the technical solutions, and advantageous effects brought by these technical features, and are further described in detail in the detailed description.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a schematic structural diagram of a conventional pole piece;

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a schematic view of another conventional pole piece structure;

FIG. 4 is a top view of FIG. 3;

fig. 5 is a schematic structural diagram of a battery cell processed by a conventional pole piece;

fig. 6 is a schematic structural diagram of a pole piece provided in the first and second embodiments of the present invention;

FIG. 7 is a top view of FIG. 6;

fig. 8 is a schematic structural diagram of another pole piece provided in the second embodiment of the present invention;

FIG. 9 is a top view of FIG. 8;

fig. 10 is a schematic structural diagram of a pole piece according to a third embodiment of the present invention;

FIG. 11 is a top view of FIG. 10;

fig. 12 is a schematic structural diagram of a pole piece according to a third embodiment of the present invention;

FIG. 13 is a top view of FIG. 12;

fig. 14 is a schematic structural diagram of a first section of a tab according to an embodiment of the present invention;

fig. 15 is a schematic structural diagram of a battery cell in a lithium ion battery according to a first embodiment of the present invention;

fig. 16 is a schematic structural diagram of a battery cell in a lithium ion battery provided in an embodiment of the present invention;

fig. 17 is a schematic structural diagram of a battery cell in a lithium ion battery provided in the third embodiment of the present invention;

fig. 18 is a schematic position diagram of thickness data acquisition according to an embodiment of the present invention;

fig. 19 is a right side view of fig. 18.

Description of reference numerals:

100-pole piece;

110-a current collector;

120-an active material layer;

130-empty foil regions;

300-pole ear;

310-a first section;

311-limiting surface;

312-a recess;

313-step;

320-a second section;

200-insulating gummed paper;

400-electric core;

420-a negative electrode sheet;

430-positive electrode sheet;

500-diaphragm.

Detailed Description

To make the objects, technical solutions and advantages of the present invention clearer, the drawings of the present invention are combined to clearly and completely describe the technical solutions of the present invention, and obviously, the described embodiments are some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Referring to fig. 1 and 2, in the conventional pole piece 100, a tab 300 is welded on the pole piece 100, and in order to prevent the edge of the active material layer 120 and burrs generated by welding the tab 300 during the production process of the pole piece 100 from piercing the separator 500 in the battery cell 400 and causing a short circuit of the battery cell 400, a certain thickness of insulating gummed paper 200 needs to be attached on the pole piece 100 to cover the burrs, thereby avoiding a safety problem. However, the thickness of the pole piece 100 may be uneven due to welding the tab 300 to the pole piece 100, attaching the adhesive tape 200, and the like.

Referring to fig. 1 and 2, an insulating gummed paper 200 is pasted on one side of a pole piece 100 on which a pole lug 300 is welded, and referring to fig. 3 and 4, the insulating gummed paper 200 is pasted on one side of the pole piece 100 on which the pole lug 300 is welded, and the insulating gummed paper 200 is also pasted on the back side of the pole lug 300, so that short circuit caused by conduction of burrs on a negative pole piece 420 and a positive pole piece 430 is avoided.

Fig. 5 is a structural view of a battery cell 400 manufactured by using the conventional pole piece 100. Especially, after the existing pole piece 100 is wound into the battery cell 400, the pole piece 100 with uneven thickness is stacked at different positions of the battery cell 400, which causes uneven thickness distribution on the plane of the battery cell 400 and poorer flatness of the battery cell 400, especially, the thickness of the innermost layer of the battery cell 400 is more uneven, and finally, the uneven stress of the pole piece 100 during formation causes the problems of uneven surface, depression, wave deformation and the like of the battery cell 400.

In view of the above background, the utility model provides a utmost point ear 300, pole piece 100 and lithium ion battery, structure through utmost point ear 300 and pole piece 100 improves, both sides at the top surface of the first section 310 of utmost point ear 300 set up undercut's concave part 312, concave part 312 is used for holding insulated adhesive tape 200, thereby it arouses pole piece 100 surface altitude variation difference great to avoid insulated adhesive tape 200 to exceed the top surface of first section 310, the thickness that leads to pole piece 100 is uneven, thereby be favorable to improving the planarization on the electric core surface that pole piece 100 structure arouses, be favorable to pole piece 100 to become electric core 400 after winding processing, thickness distribution is even, thereby pole piece 100 atress is uneven when improving into leads to electric core 400 to appear uneven surface, sunken and wave deformation scheduling problem, improve the circumstances that electric core 400 circulation inflation became invalid simultaneously.

Referring to fig. 14, the present invention provides a tab 300, the tab 300 includes a first section 310 and a second section 320 connected to the first section 310, and both sides of the top surface of the first section 310 have a recess 312 which is recessed downward. The concave portion 312 is used for accommodating the adhesive tape 200, so as to avoid the adhesive tape 200 from being higher than the top surface of the first section 310 to cause a large height variation difference on the surface of the pole piece 100, which results in uneven thickness of the pole piece 100.

Referring to fig. 14, in a possible embodiment, both sides of the top surface of the first segment 310 are provided with downward-recessed recesses 312, the recesses 312 penetrate both ends of the first segment 310 in the length direction, and the width L1 of the recesses 312 is 10mm to 15 mm; a distance H1 is provided between the bottom surface of the recess 312 and the top surface of the first section 310, and the distance H1 has a value ranging from 15 μm to 25 μm. That is, the positions 10mm to 15mm inward of both side edges in the width direction of the tab 300 are 15 μm to 25 μm thinner than the middle position of the tab; and/or the width of the first section 310 is greater than the width of the second section 320. With this arrangement, the flatness problem caused in the width direction of the first section 310 of the tab 300 can be improved.

In a possible implementation manner, the first section 310 is further provided with steps 313 at the bottom of the recess 312 on both sides, the edge of the upper end of the step 313 is in a circular arc shape, and the radius R of the circular arc shape is 1/3 times of the thickness of the first section 310; or the radius R of the circular arc is 1/6 times the thickness of the first section 310.

The edge of the upper end of the step 313 is in a circular arc-shaped structure, which is beneficial to smoothly bonding the insulation gummed paper 200 attached to the concave part 312 to the empty foil area 130, and ensures the stable bonding effect of the insulation gummed paper 200.

Referring to fig. 6 and 7, the present invention also provides a pole piece 100, including: the electrode assembly comprises a current collector 110, an active material layer 120 and a tab 300, wherein the active material layer 120 is arranged on one of the front surface and the back surface of the current collector 110 and/or the front surface and the back surface of the current collector 110, a hollow foil area 130 without the active material layer 120 is reserved at least one end of the length direction of the current collector 110, the tab 300 is arranged on the hollow foil area 130 at one end of the length direction of the current collector 110, the tab 300 comprises a first section 310 and a second section 320 connected with the first section 310, and both sides of the top surface of the first section 310 are provided with downward-recessed concave parts 312. It will be readily appreciated that the top surface of the first section 310 of the tab 300 is the side of the first section 310 facing away from the empty foil area 130.

The first section 310 of the tab 300 may be connected to the current collector 110 by welding.

Referring to fig. 8 and 9, the first section 310 of the tab 300 extends along the width direction of the current collector 110, the first section 310 is connected with the empty foil area 130 of the current collector 110, and the second section 320 is exposed outside the current collector 110.

It is easily understood that in other embodiments (not shown), the empty foil region 130 may be disposed not only at one end of the current collector 110 in the length direction, but also at the middle of the current collector 110.

It is easily understood that the length direction of the first section 310 is the width direction of the current collector 110, and the width direction of the first section 310 is the length direction of the current collector 110.

The pole piece 100 that this embodiment provided, improve through the structure to utmost point ear 300, both sides at the first section 310 of utmost point ear 300's top surface set up undercut's concave part 312, concave part 312 is used for holding insulated adhesive tape 200, thereby it is poor great to avoid insulated adhesive tape 200 to exceed the top surface of first section 310 to arouse pole piece 100 surface altitude variation, lead to pole piece 100's thickness inequality, make a pole piece 100 that this embodiment provides be favorable to improving the smoothness on the electric core surface that pole piece 100 structure arouses, reduce because the difference in height between the first section 310 of utmost point ear 300 and the mass flow body 110 influences the roughness of pole piece 100 self, be favorable to after pole piece 100 is processed into electric core, improve the relatively poor problem of electric core surface smoothness.

It is easily understood that, referring to fig. 10 and 12, in one of the pole pieces 100 provided in the present embodiment, the active material layer 120 may be disposed on both the front and back surfaces of the partial current collector 110, the active material layer 120 may be disposed on one of the front and back surfaces of the partial current collector 110, and the active material layer 120 may not be disposed on both the front and back surfaces of the remaining partial current collector 110. As shown in fig. 12 and 13, the empty foil area 130 formed by not disposing the active material layer 120 on both the front and back surfaces of the current collector 110 is located at least one end of the current collector 110 in the length direction.

In one possible implementation, referring to fig. 7 and 11, the empty foil region 130 is rectangular, and a side surface of the first section 310 close to the active material layer 120 is a limiting surface 311 along a width direction of the first section 310, and a distance H2 is provided between an end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311. Referring to fig. 7 and 14, the spacing H2 is greater than 2 times the thickness H of the first segment 310, and the difference between the spacing H2 and 2 times the thickness H of the first segment 310 is δ 1, where δ 1 has a value in the range of: delta 1 is more than or equal to 2mm and less than or equal to 10 mm.

By limiting the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311, on one hand, the influence on the width of the battery cell 400 when the pole piece 100 is bent can be avoided, and the width of the battery cell 400 is prevented from being increased; on the other hand, by limiting the distance H2 between the end face of the active material layer 120 close to the limiting face 311 and the limiting face 311, damage to the active material layer 120 can be reduced in the process of winding the pole piece 100 into the battery cell 400.

In a possible implementation manner, the present embodiment provides a pole piece 100 further comprising an insulating adhesive paper 200, wherein at least the inside of the recess 312 of the tab 300 and at least a part of the empty foil area 130 of the pole piece 100 are covered with the insulating adhesive paper 200.

In one possible embodiment, the thickness of the adhesive paper 200 is 15 μm to 25 μm.

The concave part 312 is used for accommodating the adhesive tape 200, and a distance H1 is provided between the bottom surface of the concave part 312 and the top surface of the first section 310, so that after the adhesive tape 200 is attached to the first section 310, part of the adhesive tape 200 covers the concave part 312, and the distance H1 between the bottom surface of the concave part 312 and the top surface of the first section 310 is filled with the adhesive tape 200 by the thickness of the adhesive tape 200, so that the height difference between the adhesive tape 200 and the top surface of the first section 310 is reduced, the uneven thickness of the pole piece 100 caused by the large height difference of the surface of the pole piece 100 is avoided, and the flatness of the surface of the battery cell processed by the pole piece 100 is improved.

In one possible implementation, the first section 310 extends along the width direction of the current collector 110, and the length of the first section 310 is 40% to 105% of the width of the current collector 110. In a preferred embodiment, the length of the first section 310 is 80% to 105% of the width of the current collector 110. By adopting the structure, the thickness distribution of the pole piece 100 in the length direction is improved, and the uniform thickness distribution is facilitated after the pole piece 100 is wound into the battery cell 400, so that the problems of uneven surface, depression, wave deformation and the like of the battery cell 400 caused by uneven stress of the pole piece 100 during formation are improved, and the condition of failure of the battery cell 400 due to cyclic expansion is improved.

In one possible implementation, the length of the first section 310 is 100% of the width of the current collector 110, i.e., the length of the first section 310 is equal to the width of the current collector 110.

In one possible embodiment, the thickness of the second section 320 is equal to the thickness of the first section 310, and the thickness h of the first section 310 has a value in the range of: h is more than or equal to 45 mu m and less than or equal to 115 mu m. After the first segment 310 is disposed on the empty foil area 130, it is avoided that the surface of the battery cell processed by the pole piece 100 is affected by an excessive protrusion of the first segment 310 on the empty foil area 130 due to an excessive thickness h of the first segment 310.

The utility model provides a lithium ion battery, including electric core 400, refer to fig. 15 and show, electric core 400 includes negative electrode piece 420, positive electrode piece 430, and the diaphragm 500 of interval negative electrode piece 420 and positive electrode piece 430, negative electrode piece 420 and positive electrode piece 430 are foretell pole piece 100, negative electrode piece 420, positive electrode piece 430 and the range upon range of back of diaphragm 500 convolute and constitute electric core 400, electric core 400 has the circle layer that radially outwards sets up a plurality of coiling in proper order along electric core 400 and forms, utmost point ear 300 on the negative electrode piece 420 is located the inner circle layer of electric core 400, or utmost point ear 300 on the negative electrode piece 420 is located the outer circle layer of electric core 400.

The utility model provides a pair of among lithium ion battery, its electric core 400 includes above-mentioned pole piece 100, therefore when negative electrode piece 420 and positive electrode piece 430 make electric core 400 through the coiling, the thickness distribution that is favorable to electric core 400 is even, improves the uneven electricity core 400 that leads to of pole piece 100 atress when finally becoming and appears the uneven surface, sunken and wave deformation scheduling problem.

Because the first section 310 is welded on the empty foil area 130 to generate a burr, in order to avoid the burr from piercing the diaphragm 500 to cause a short circuit of the battery cell, the insulating gummed paper 200 needs to be pasted to cover the burr, and the concave portion 312 is used for accommodating the insulating gummed paper 200, so that after the insulating gummed paper 200 is pasted, the surface of the pole piece 100 is uneven due to the fact that the height variation difference on the surface of the pole piece 100 is large, and the surface evenness of the battery cell is influenced after the pole piece 100 is processed into the battery cell.

In a possible implementation manner, referring to fig. 13, a side surface of the first section 310 of the tab 300, which is close to the active material layer 120 of the pole piece 100, is a limiting surface 311, and a distance H2 is provided between an end surface of the active material layer 120, which is close to the limiting surface 311, and the limiting surface 311; referring to fig. 7 and 14, the spacing H2 is greater than 2 times the thickness H of the first segment 310, and the difference between the spacing H2 and 2 times the thickness H of the first segment 310 is δ 1, where δ 1 has a value in the range of: delta 1 is more than or equal to 2mm and less than or equal to 10 mm; and/or the spacing H2 is greater than pi/2 times the thickness T of the cell 400, and the difference between the spacing H2 and pi/2 times the thickness T of the cell 400 is δ 2, the range of values for δ 2 being: delta 2 is more than or equal to 1mm and less than or equal to 5mm, or delta 2 is more than or equal to 1mm and less than or equal to 4 mm.

With such a structure, on one hand, the width influenced by the bending of the pole piece 100 can be avoided when the battery cell 400 is manufactured, and the width of the battery cell 400 is prevented from increasing; on the other hand, by limiting the distance H2 between the end face of the active material layer 120 close to the limiting face 311 and the limiting face 311, a sufficient distance is provided between the limiting face 311 of the tab 300 and the active material layer 120, so that in the process of winding the pole piece 100 into the battery cell 400, the damage to the active material layer 120 can be reduced, and the coated active material layer 120 is prevented from dropping off when part of the active material layer 120 is located at the position where the curvature of the pole piece 100 is extremely small.

In one possible implementation, when the tab 300 on the negative electrode sheet 420 and/or the tab 300 on the positive electrode sheet 430 are located on the inner ring layer of the battery cell 400, the width D of the tab 300 on the negative electrode sheet 420 and/or the tab 300 on the positive electrode sheet 430 satisfies:

the inner width L2-spacing H2-1mm of the battery cell 400 is more than or equal to D which is more than or equal to the inner width L2-spacing H2-5mm of the battery cell 400;

the inner width L2 of the battery cell 400 is the width of the inner ring layer of the battery cell 400 in the orthogonal projection direction of the battery cell 400.

In one possible implementation, when the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 are located on the outer ring layer of the battery cell 400, the width D of the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 satisfies:

the external width L3 of the battery cell 400, namely the thickness T-1mm of the battery cell 400, is more than or equal to D, and is more than or equal to the external width L3 of the battery cell 400, and the thickness T-5mm of the battery cell 400;

the outer width L3 of the battery cell 400 is the width of the outer ring layer of the battery cell 400 in the orthogonal projection direction of the battery cell 400, and the thickness T of the battery cell 400 is the height of the outer ring layer of the battery cell 400 in the lateral projection direction of the battery cell 400.

In a possible implementation manner, when the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 are located on the inner ring layer of the battery cell 400, as shown in fig. 14, the edge of the upper end of the step 313 of the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 is in a circular arc shape, and the radius R of the circular arc shape is 1/6 times the thickness of the first section 310.

In a possible implementation manner, when the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 are located on the outer ring layer of the battery cell 400, the edge of the upper end of the step 313 of the tab 300 on the negative electrode tab 420 and/or the tab 300 on the positive electrode tab 430 is in a circular arc shape, and the radius R of the circular arc shape is 1/3 times the thickness of the first section 310.

It is easily understood that the present embodiment provides a lithium ion battery, which further includes an encapsulation casing, the battery cell 400 is accommodated in the encapsulation casing, and the encapsulation casing is filled with an electrolyte.

In this embodiment, the materials of the current collector 110 in the negative electrode sheet 420 and the positive electrode sheet 430 may be set according to actual needs, and are not further limited herein. For example, the current collector 110 in the positive electrode sheet 430 may be an aluminum foil, and the current collector 110 in the negative electrode sheet 420 may be a copper foil.

In this embodiment, the kind and ratio of the active material in active material layer 120 in negative electrode sheet 420 and positive electrode sheet 430 may be set according to actual needs, and are not further limited herein. For example, the active material in the active material layer 120 in the negative electrode sheet 420 may include graphite, hard carbon, silicon monoxide, and the like, and the active material in the active material layer 120 in the positive electrode sheet 430 may include lithium cobaltate, lithium iron phosphate, lithium manganate, and the like.

The separator 500 may include a substrate, which may be a Polyethylene (PE) monolayer film, a polypropylene (PP) monolayer film, or a polypropylene-polyethylene-polypropylene three-layer composite film, and a coating layer, which may be at least one of porous silicon dioxide, aluminum oxide, titanium dioxide, and zirconium dioxide.

Example one

Referring to fig. 15, when the tab 300 on the negative electrode tab 420 and the tab 300 on the positive electrode tab 430 are both located on the inner ring layer of the battery cell 400:

in the width direction along the first segment 310, one side surface of the first segment 310 close to the active material layer 120 is a stopper surface 311, and a distance between one end surface of the active material layer 120 close to the stopper surface 311 and the stopper surface 311 is a distance H2. The spacing H2 is greater than 2 times the thickness H of the first segment 310, and the difference between the spacing H2 and 2 times the thickness H of the first segment 310 is δ 1, where δ 1 has a value in the range of: delta 1 is more than or equal to 2mm and less than or equal to 10 mm.

The inner width L2 of the battery cell 400 is the width of the inner ring layer of the battery cell 400 in the orthogonal projection direction, and the widths D of the tab 300 on the negative electrode plate 420 and the tab 300 on the positive electrode plate 430 both satisfy:

the inner width L2-spacing H2-1mm of the battery cell 400 is more than or equal to D, and the inner width L2-spacing H2-5mm of the battery cell 400 is more than or equal to 0.

In the tab 300 on the negative electrode sheet 420 and the tab 300 on the positive electrode sheet 430, the edge of the upper end of the step 313 of the tab 300 is arc-shaped, and the radius R of the arc-shaped is 1/6 times of the thickness of the first section 310.

The lengths of the tab 300 on the negative electrode plate 420 and the tab 300 on the positive electrode plate 430 satisfy: the length of the first section 310 is 40% to 105% of the width of the current collector 110.

The thickness of the second section 320 is equal to the thickness of the first section 310, and the thickness h of the first section 310 has a value in the range: h is more than or equal to 45 mu m and less than or equal to 115 mu m.

The length and width of the second section 320 and the position of the second section 320 in the first section 310 may be determined according to the use requirement.

Example two

Referring to fig. 16, when the tab 300 on the negative electrode sheet 420 is located on the inner circle layer of the battery cell 400, and the tab 300 on the positive electrode sheet 430 is located on the outer circle layer of the battery cell 400:

for tab 300 on negative electrode tab 420:

The inner width L2 of the battery cell 400 is the width of the inner ring layer of the battery cell 400 in the orthographic projection direction, and the width D of the tab 300 on the negative electrode tab 420 satisfies:

In tab 300 on negative electrode tab 420: the edges of the upper ends of the steps 313 of the tab 300 are all arc-shaped, and the radius R of the arc shape is 1/6 times of the thickness of the first section 310.

For the tab 300 on the positive electrode sheet 430:

in the width direction of the first segment 310, one side surface of the first segment 310 close to the active material layer 120 is a limiting surface 311, and a distance H2 is provided between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311. The distance H2 is greater than pi/2 times the thickness T of the cell 400, and the difference between the distance H2 and pi/2 times the thickness T of the cell 400 is δ 2, where the value range of δ 2 is: delta 2 is more than or equal to 1mm and less than or equal to 5 mm.

The outer width L3 of the battery cell 400 is the width of the outer ring layer of the battery cell 400 in the orthogonal projection direction of the battery cell 400, the thickness T of the battery cell 400 is the height of the outer ring layer of the battery cell 400 in the side projection direction, and the width D of the tab 300 on the positive electrode plate 430 satisfies:

the external width L3 of the battery cell 400, the thickness T-1mm of the battery cell 400 is more than or equal to D, the external width L3 of the battery cell 400, and the thickness T-5mm of the battery cell 400 is more than or equal to 0.

In the tab 300 on the positive electrode sheet 430: the edges of the upper ends of the steps 313 of the tab 300 are all arc-shaped, and the radius R of the arc shape is 1/3 times of the thickness of the first section 310.

With such a structure, on one hand, the width influenced by the bending of the pole piece 100 can be avoided when the battery cell 400 is manufactured, and the width of the battery cell 400 is prevented from increasing; on the other hand, by limiting the distance H2 between the end face of the active material layer 120 close to the limiting face 311 and the limiting face 311, a sufficient distance is provided between the limiting face 311 of the tab 300 and the active material layer 120, so that in the process of winding the pole piece 100 into the battery cell 400, damage to the active material layer 120 can be reduced, and the active material layer 120 can be prevented from falling off when part of the active material layer 120 is located at a position where the curvature of the pole piece 100 is extremely small, for example, at the bending position of the pole piece 100 located at the innermost circle of the battery cell 400.

EXAMPLE III

Referring to fig. 17, when the tab 300 on the positive electrode tab 430 is located on the inner ring layer of the battery cell 400, and the tab 300 on the negative electrode tab 420 is located on the outer ring layer of the battery cell 400:

for the tab 300 on the positive electrode sheet 430:

The inner width L2 of the battery cell 400 is the width of the inner ring layer of the battery cell 400 in the orthographic projection direction, and the width D of the tab 300 on the positive electrode plate 430 satisfies:

The edge of the upper end of the step 313 of the tab 300 on the positive electrode sheet 430 is arc-shaped, and the radius R of the arc is 1/6 times of the thickness of the first section 310.

For tab 300 on negative electrode tab 420:

in the width direction of the first segment 310, one side surface of the first segment 310 close to the active material layer 120 is a limiting surface 311, and a distance H2 is provided between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311. The distance H2 is greater than pi/2 times the thickness T of the cell 400, and the difference between the distance H2 and pi/2 times the thickness T of the cell 400 is δ 2, where the value range of δ 2 is: delta 2 is more than or equal to 1mm and less than or equal to 4 mm.

The outer width L3 of the battery cell 400 is the width of the outer ring layer of the battery cell 400 in the orthogonal projection direction, the thickness T of the battery cell 400 is the height of the battery cell 400 in the lateral projection direction of the battery cell 400, and the width D of the tab 300 on the negative electrode plate 420 satisfies:

In tab 300 on negative electrode tab 420: the edges of the upper ends of the steps 313 of the tab 300 are all arc-shaped, and the radius R of the arc shape is 1/3 times of the thickness of the first section 310.

The embodiment of the utility model provides a pair of lithium ion battery, the roughness of the thickness spatial adjustment electric core of make full use of electricity core self, and do not increase electricity core self thickness, do not influence electric core energy density, reach the purpose that roughness and energy degree were compromise.

The embodiment of the utility model provides a pair of lithium ion battery, through improving utmost point ear 300's structure, can effectively improve the thickness distribution of electric core 400 inner circle one deck, improve when becoming because pole piece 100 atress is uneven to lead to pole piece 100 to appear uneven, sunken and wave deformation scheduling problem.

The embodiment of the utility model provides a pair of lithium ion battery, its even formation pressure can also effectively improve the bad problem of diaphragm 500 bonding, improves the poor interface department of arousing of cohesiveness between charge-discharge cycle later stage pole piece 100 and diaphragm 500 and analyse the problem of lithium, also can improve the roughness of electric core 400.

The utility model provides a pair of lithium ion battery can effectively improve long cycle in-process can be because the roughness problem of electricity core 400, and it is inhomogeneous to lead to the internal stress that electricity core 400 receives at cyclic expansion in-process pole piece 100, finally leads to electric core 400 face of bonding to become invalid, and electricity core 400 bulging deformation causes the problem of capacity decay, inflation inefficacy, promotes lithium ion battery's cycle life and security performance.

The utility model provides a pair of pole piece 100 is applicable to all electric core models, explains below with lithium ion battery's electric core 400 as an example, can explain for example with the lithium ion battery that the model is "366283" as an example:

example 1

Example one as an example of embodiment one:

referring to fig. 15, the tab 300 on the negative electrode tab 420 and the tab 300 on the positive electrode tab 430 are both located on the inner circle layer of the battery cell 400, the outer width L3 of the battery cell 400 is 60mm, the inner width L2 of the battery cell 400 is 57mm, and the height of the battery cell 400 is 80 mm.

In the positive electrode sheet 430: the width of the pole piece 100 is 75.5mm, the length of the empty foil area 130 on the positive pole piece 430 where the tab 300 is mounted is 55mm, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 50mm, and the length of the first section 310 of the tab 300 is 75.5 mm. The distance H1 between the bottom surface of the recess 312 and the top surface of the first segment 310 has a value of 15 μm, i.e., the position 10mm inward of the widthwise edge of the tab 300 is 15 μm thinner than the middle position of the tab, and the edges of the upper ends of the two steps 313 of the tab 300 are required to be rounded with a radius R of a circular arc shape 1/6 times the thickness of the first segment 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 4mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

In the negative electrode sheet 420: the width of the pole piece 100 is 77.5mm, the length of the empty foil area 130 on which the tab 300 is mounted on the negative pole piece 420 is 56mm, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 50mm, and the length of the first section 310 of the tab 300 is 75.5 mm. The distance H1 between the bottom surface of the recess 312 and the top surface of the first segment 310 has a value of 15 μm, i.e., the position 10mm inward of the widthwise edge of the tab 300 is 15 μm thinner than the middle position of the tab 300, and the edges of the upper ends of the two steps 313 of the tab 300 are required to be rounded with a radius R of a rounded arc shape 1/6 times the thickness of the first segment 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 5mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

Example two

Example two as an example of embodiment two:

referring to fig. 16, the tab 300 on the negative electrode tab 420 is located on the inner circle layer of the battery cell 400, the tab 300 on the positive electrode tab 430 is located on the outer circle layer of the battery cell 400, the outer width L3 of the battery cell 400 is 60mm, the inner width L2 of the battery cell 400 is 57mm, and the height of the battery cell 400 is 80 mm.

In the positive electrode sheet 430: the width of the pole piece 100 is 75.5mm, the length of the empty foil area 130 for mounting the tab 300 on the positive electrode piece 430 is 85mm, the tab 300 on the positive electrode piece 430 is arranged on the outer ring layer of the battery core 400, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 55mm, the length of the first section 310 of the tab 300 is 75.5mm, the distance H1 between the bottom surface of the recess 312 and the top surface of the first section 310 is 15 μm, that is, the position of the inward 10mm of the edge in the width direction of the tab 300 is 15 μm thinner than the middle position of the tab, and the edges of the upper ends of two steps 313 of the tab 300 both need to be rounded corners, and the radius R of the circular arc is 1/3 times of the thickness of the first section 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 5mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

In the negative electrode sheet 420: the width of the pole piece 100 is 77.5mm, the length of the empty foil area 130 on which the tab 300 is mounted on the negative pole piece 420 is 56mm, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 50mm, and the length of the first section 310 of the tab 300 is 77.5 mm. The distance H1 between the bottom surface of the recess 312 and the top surface of the first segment 310 has a value of 15 μm, i.e., the position 10mm inward of the widthwise edge of the tab 300 is 15 μm thinner than the middle position of the tab 300, and the edges of the upper ends of the two steps 313 of the tab 300 are required to be rounded with a radius R of a rounded arc shape 1/6 times the thickness of the first segment 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 5mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

Example three

Example three as an example of embodiment three:

referring to fig. 17, the tab 300 on the positive electrode plate 430 is located on the inner circle layer of the battery cell 400, the tab 300 on the negative electrode plate 420 is located on the outer circle layer of the battery cell 400, the outer width L3 of the battery cell 400 is 60mm, the inner width L2 of the battery cell 400 is 57mm, and the height of the battery cell 400 is 80 mm.

In the positive electrode sheet 430: the width of the pole piece 100 is 75.5mm, the length of the empty foil area 130 for mounting the tab 300 on the positive electrode piece 430 is 55mm, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 50mm, the length of the first section 310 of the tab 300 is 75.5mm, the distance H1 between the bottom surface of the recess 312 and the top surface of the first section 310 is 15 μm, that is, the position of the inward 10mm of the edge of the tab 300 in the width direction is 15 μm thinner than the middle position of the tab, and the edges of the upper ends of two steps 313 of the tab 300 are required to be rounded, and the radius R of the circular arc is 1/6 times of the thickness of the first section 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 4mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

In the negative electrode sheet 420: the width of the pole piece 100 is 77.5mm, the length of the empty foil area 130 on which the tab 300 is mounted on the negative pole piece 420 is 63mm, the tab 300 on the negative pole piece 420 is arranged on the outer ring layer of the battery core 400, the thickness of the tab 300 is 80 μm, the width of the tab 300 is 54mm, and the length of the first section 310 of the tab 300 is 77.5 mm. The distance H1 between the bottom surface of the recess 312 and the top surface of the first segment 310 has a value of 15 μm, i.e., the position 10mm inward of the widthwise edge of the tab 300 is 15 μm thinner than the middle position of the tab, and the edges of the upper ends of the two steps 313 of the tab 300 each require rounded corners having a radius R of a rounded arc 1/3 times the thickness of the first segment 310. When the tab 300 is welded, the distance H2 between one end surface of the active material layer 120 close to the limiting surface 311 and the limiting surface 311 is 5mm, the thickness of the second section 320 is equal to the thickness of the first section 310, and the length, the width and the position of the protruding end of the second section 320 can be determined according to the use requirement.

Referring to fig. 18 and 19, using a conventional battery cell 400 as a comparative example, and using the battery cells 400 of examples 1, 2, and 3, thickness distributions of 7 different positions a, b, c, d, e, f, and g were selected, and thickness data were collected, and cycle test data are shown in table 1 below:

TABLE 1

The thickness is tested by using a 3D high-resolution microscope, certain errors exist in measurement due to operation problems, but the errors can be controlled within an error range of 0.01mm, meanwhile, in the battery preparation process, the errors exist in a design value and an actual measurement value due to the influence of factors such as the thickness difference of a coating pole piece, and basically the controllable errors are within a range of 0.03 mm.

Through the data in the analysis table 1, learn to improve through the structure to utmost point ear 300 and pole piece 100, can effectively improve the thickness distribution of the one deck of electric core 400 innermost circle layer, pole piece 100 atress is uneven when improving into leads to electric core 400 to appear the surface not smooth, sunken and wave deformation scheduling problem, even formation pressure can also effectively improve the poor problem of diaphragm 500 bonding, it is poor to improve the cohesiveness between circulation later stage pole piece 100 and diaphragm 500, cause the problem of lithium analysis, improve the roughness of electric core 400, change the condition that the circulation inflation became invalid simultaneously.

The utility model provides a pair of lithium ion battery can effectively improve long cycle in-process can be because the roughness problem of electricity core 400, and it is inhomogeneous to lead to the internal stress that electricity core 400 received at circulation inflation in-process pole piece 100, finally leads to electricity core 400 to bond cross-section inefficacy, electric core 400 dilatational strain, causes the problem of capacity decay, inflation inefficacy, promotes battery cycle life and security performance.

It should be noted that the numerical values and numerical ranges referred to in this application are approximate values, and there may be some error due to the manufacturing process, and the error may be considered to be negligible by those skilled in the art.

In the description of the present invention, it is to be understood that the terms "center", "length", "width", "thickness", "top", "bottom", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "axial", "circumferential", and the like, which are used to indicate the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for convenience of description and simplification of the description, and do not indicate or imply that the position or element referred to must have a particular orientation, be of particular construction and operation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly, e.g., as meaning fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; either directly or indirectly through intervening media, such as through internal communication or through an interaction between two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

In the present disclosure, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise direct contact between the first and second features, or may comprise contact between the first and second features not directly. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention.

Claims

1. A pole ear, characterized in that, comprises a first section (310) and a second section (320) connected with the first section (310), both sides of the top surface of the first section (310) are provided with a concave part (312) which is concave downwards.

2. The tab as claimed in claim 1, wherein the recesses (312) penetrate through both ends of the first segment (310) in the length direction, and the width L1 of the recesses (312) is 10mm to 15 mm; a distance H1 is arranged between the bottom surface of the concave part (312) and the top surface of the first section (310), and the value of the distance H1 is 15-25 μm; and/or

The width of the first section (310) is greater than the width of the second section (320).

3. The tab as claimed in claim 2, wherein the first section (310) is further provided with steps (313) at the bottom of the recess (312) on both sides, the edge of the upper end of the step (313) is in the shape of a circular arc, and the radius R of the circular arc is 1/3 times the thickness of the first section (310); or

The radius R of the circular arc is 1/6 times the thickness of the first segment (310).

4. A pole piece, comprising: a current collector (110), an active material layer (120), and the tab (300) according to any one of claims 1 to 3, wherein the active material layer (120) is disposed on one of the front and back surfaces of the current collector (110) and/or the front and back surfaces of the current collector (110), at least one end of the length direction of the current collector (110) is left with a hollow foil area (130) where the active material layer (120) is not disposed, the tab (300) is disposed on the hollow foil area (130) of the current collector (110), the tab (300) comprises a first section (310) and a second section (320) connected with the first section (310), and both sides of the top surface of the first section (310) are provided with a recess (312) recessed downwards.

5. The pole piece of claim 4, wherein the first section (310) extends along a width direction of the current collector (110), and a length of the first section (310) is 40% to 105% of the width of the current collector (110).

6. A lithium ion battery comprising a battery cell (400), wherein the battery cell (400) comprises a negative electrode sheet (420), a positive electrode sheet (430), and a diaphragm (500) separating the negative electrode sheet (420) and the positive electrode sheet (430), the negative electrode sheet (420) and the positive electrode sheet (430) are the electrode sheets (100) of any one of claims 4 to 5, the negative electrode sheet (420), the positive electrode sheet (430), and the diaphragm (500) are laminated and then wound to form the battery cell (400), and the battery cell (400) has a plurality of coil layers sequentially wound outward;

the pole lug (300) on the negative electrode plate (420) is positioned on the inner ring layer of the battery cell (400), or the pole lug (300) on the negative electrode plate (420) is positioned on the outer ring layer of the battery cell (400).

7. The lithium ion battery according to claim 6, characterized in that, a side of the first section (310) of the tab (300) close to the active material layer (120) of the pole piece (100) is a limiting surface (311), and a distance H2 is provided between one end surface of the active material layer (120) close to the limiting surface (311) and the limiting surface (311);

the separation H2 is greater than 2 times the thickness H of the first segment (310), and the difference between the separation H2 and 2 times the thickness H of the first segment (310) is δ 1, the value of δ 1 ranging from: delta 1 is more than or equal to 2mm and less than or equal to 10 mm; and/or

The distance H2 is greater than pi/2 times the thickness T of the battery cell (400), the difference between the distance H2 and pi/2 times the thickness T of the battery cell (400) is delta 2, and the numerical range of the delta 2 is as follows: delta 2 is more than or equal to 1mm and less than or equal to 5mm or delta 2 is more than or equal to 1mm and less than or equal to 4 mm.

8. The lithium ion battery according to claim 7, wherein when the tab (300) on the negative electrode sheet (420) and/or the tab (300) on the positive electrode sheet (430) are located on the inner ring layer of the battery cell (400), the width D of the tab (300) on the negative electrode sheet (420) and/or the tab (300) on the positive electrode sheet (430) satisfies:

the inner width L2-the distance H2-1mm of the battery cell (400) is more than or equal to D and is more than or equal to the inner width L2-the distance H2-5mm of the battery cell (400);

wherein the inner width L2 of the battery cell (400) is the width of the innermost ring layer of the battery cell (400) in the orthographic projection direction of the battery cell (400).

9. The lithium ion battery according to claim 8, wherein when the tab (300) on the negative electrode sheet (420) and/or the tab (300) on the positive electrode sheet (430) are located on the outer ring layer of the battery cell (400), the width D of the tab (300) on the negative electrode sheet (420) and/or the tab (300) on the positive electrode sheet (430) satisfies:

the external width L3 of the battery cell (400), namely the thickness T-1mm of the battery cell (400) is more than or equal to D, the external width L3 of the battery cell (400), and the thickness T-5mm of the battery cell (400) are more than or equal to D;

the outer width L3 of the battery cell (400) is the width of the outer ring layer of the battery cell (400) in the orthographic projection direction of the battery cell (400), and the thickness T of the battery cell (400) is the height of the outer ring layer of the battery cell (400) in the lateral projection direction of the battery cell (400).

10. The lithium ion battery according to claim 9, wherein when the tab (300) on the negative electrode sheet (420) and/or the tab (300) on the positive electrode sheet (430) are positioned on the inner ring layer of the battery cell (400), the edge of the upper end of the step (313) of the tab (300) is in a circular arc shape, and the radius R of the circular arc shape is 1/6 times the thickness of the first section (310); or

When the tab (300) on the negative electrode plate (420) and/or the tab (300) on the positive electrode plate (430) are positioned on the outer ring layer of the battery core (400), the edge of the upper end of the step (313) of the tab (300) is arc-shaped, and the radius R of the arc-shaped is 1/3 times of the thickness of the first section (310).