CN213936240U

CN213936240U - Negative pole piece and lithium ion battery

Info

Publication number: CN213936240U
Application number: CN202021076826.3U
Authority: CN
Inventors: 不公告发明人
Original assignee: Evergrande New Energy Technology Shenzhen Co Ltd
Current assignee: Evergrande New Energy Technology Shenzhen Co Ltd
Priority date: 2020-06-11
Filing date: 2020-06-11
Publication date: 2021-08-10
Anticipated expiration: 2030-06-11

Abstract

The utility model belongs to the technical field of lithium ion battery, more specifically say, relate to a negative pole piece and lithium ion battery. The negative pole piece comprises a current collector and a coating layer covering the surface of the current collector, the current collector is provided with a main body part and edge parts arranged on two side parts of the main body part, the coating layer comprises a middle layer and edge layers arranged on two side parts of the middle layer, the inner edges of the edge layers are tightly attached to the outer edges of the middle layer, the middle layer correspondingly covers the main body part, the edge layers correspondingly cover the edge parts, the negative pole capacity per unit area of the edge layers is higher than that of the negative pole capacity per unit area of the middle layer, the negative pole capacity per unit area of the middle layer is equal to the preset negative pole capacity per unit area, therefore, the negative pole capacity of the edge layers of the coating layer is increased, even if the thickness of the outer edge of the edge layer is reduced due to the flowing of the slurry, the negative electrode capacity of the edge layer is not lower than the designed negative electrode capacity, and the negative electrode capacity of the negative electrode plate is prevented from being reduced, so that the lithium precipitation risk of the negative electrode plate is effectively reduced, and the safety performance is improved.

Description

Negative pole piece and lithium ion battery

Technical Field

The utility model belongs to the technical field of lithium ion battery, more specifically say, relate to a negative pole piece and lithium ion battery.

Background

Among a plurality of chemical energy storage products, the lithium ion battery has the characteristics of high energy density, high power density, long service life and the like, shows great market advantages, is widely applied to various portable electronic products such as mobile phones, flat panels, electronic watches and the like, and in recent years, along with the continuous improvement and development of the lithium ion battery technology, the application and the demand of the lithium ion battery in the field of electric vehicles and the like which need large-scale energy storage are gradually increased. However, the lithium ion battery in the prior art still has some defects in the using process, for example, the traditional negative pole piece is easy to generate a lithium separation phenomenon, once the lithium separation phenomenon occurs, the separated metal lithium is oxidized into lithium ions, which causes battery capacity attenuation and battery energy storage density reduction, and in addition, the separated metal lithium forms lithium dendrites, and the dendrites may puncture the diaphragm due to continuous growth, thereby inducing battery short circuit, generating irreversible influence on the service life and safety of the lithium ion battery, and even possibly causing safety accidents in severe cases.

In the process of manufacturing the positive and negative pole pieces, when the surface of the current collector is coated with active material slurry, the slurry is a solid-liquid mixture with certain fluidity, so that the coated slurry flows and extends towards the edge of the current collector and can form an edge casting area at the edge of the current collector, and further the coating thickness of the slurry at the edge of the current collector is smaller than the designed coating thickness, the NP ratio (negative capacity per unit area/positive capacity per unit area) of the edge area of the positive and negative pole pieces after the electric core is wound is reduced, so that the edge of the negative pole piece has a large lithium precipitation risk, and in addition, the edge of the pole piece generally has larger current density, so that the deposition speed of lithium at the edge of the negative pole piece can be accelerated, and the occurrence of the lithium precipitation phenomenon is accelerated. In order to solve the problem, when the pole piece is manufactured, the size of the negative pole piece is slightly larger than that of the positive pole piece, namely, the allowance size is designed between the positive pole piece and the negative pole piece, however, in order to ensure the normal winding of the battery cell, the sizes of the positive pole piece and the negative pole piece are not too different, however, the size of the thinning of the edge of the negative pole piece due to casting is far larger than the allowance size which can be reserved between the positive pole piece and the negative pole piece when the slurry is coated, and the occurrence of lithium precipitation of the negative pole piece cannot be effectively avoided.

SUMMERY OF THE UTILITY MODEL

An object of the embodiment of the utility model is to provide a negative pole piece and lithium ion battery to lithium ion battery among the solution prior art easily takes place at negative pole piece edge and analyse the technical problem of lithium.

In order to achieve the above object, the utility model adopts the following technical scheme: the utility model provides a negative pole piece, including the mass flow body and cover in the dressing layer on the mass flow body surface, the mass flow body is including the main part that is located the middle part and set up in the edge part of the relative both sides portion of main part along length direction, the dressing layer includes middle part layer and sets up in the marginal layer of the relative both sides portion of middle part layer along length direction, the middle part layer corresponds and covers the main part, the marginal layer corresponds and covers the edge part, the unit area negative pole capacity on marginal layer is higher than the unit area negative pole capacity on middle part layer, the unit area negative pole capacity on middle part layer equals with predetermineeing unit area negative pole capacity.

By adopting the technical scheme, the coating layer is divided into the middle layer and the edge layer, the middle layer correspondingly covers the main body part of the current collector, and the edge layer correspondingly covers the edge part of the current collector.

Optionally, the gram capacity of the active material in the edge layer is higher than the gram capacity of the active material in the central layer.

By adopting the technical scheme, the active material with high gram capacity is selected to ensure that the negative electrode capacity per unit area of the edge layer is higher than that of the middle layer, the control of the negative electrode capacity per unit area of the edge layer and the middle layer can be realized by depending on the selection of the active material, and the actual control of the negative electrode capacity per unit area is more convenient.

Optionally, the gram capacity of the active substance in the middle layer is one or more of graphite, hard carbon, soft carbon, silicon-carbon composite material, silicon-oxygen compound, carbon microsphere intermediate phase, lithium titanate and other active substances with the gram capacity of 250 mAh/g-400 mAh/g, and the gram capacity of the active substance in the edge layer is one or more of graphite, hard carbon, soft carbon, silicon-carbon composite material, silicon-oxygen compound, carbon microsphere intermediate phase, lithium titanate and other active substances with the gram capacity of 300 mAh/g-450 mAh/g.

By adopting the technical scheme, different active substances are selected within the gram volume numerical range according to the selection requirements of the edge layer and the middle layer on the gram volume of the active substances, the selection range of the active substances is narrowed, and the calculation difficulty is prevented from being increased due to mass selection.

Optionally, the width of the edge layer is 0.5mm to 50 mm.

By adopting the technical scheme, the width of the edge layer is ensured to be larger than or equal to the width of the region with gradually reduced thickness of the coating layer on the traditional negative pole piece due to casting or edge effect, so that the reduction of the negative pole capacity caused by casting or edge effect can be counteracted by arranging the edge layer.

Preferably, the width of the edge layer is 5mm to 15 mm.

By adopting the technical scheme, the width of the edge layer can be ensured, and the lithium separation phenomenon can not occur on the edge of most of the negative pole pieces.

Optionally, the height of the surface of the edge layer facing away from the edge portion is no higher than the height of the surface of the central layer facing away from the main body portion.

By adopting the technical scheme, the phenomenon that the edge of the negative pole piece bulges due to overhigh setting of the thickness of the edge layer is avoided, and the negative pole piece is prevented from cracking and falling powder.

Optionally, the outer edge of the middle layer extends with a casting lip towards the edge layer, and the inner edge of the edge layer extends with a lapping lip towards the middle layer;

or the inner edge of the edge layer extends towards the middle layer to form a casting edge part, and the outer edge of the middle layer extends towards the edge layer to form a lap joint edge part;

the overlapping edge part covers the casting edge part.

Through adopting above-mentioned technical scheme, when not scribbling middle part layer and edge layer simultaneously, the outward flange on middle part layer (the inward flange on edge layer) can appear the curtain coating marginal part because of curtain coating or edge effect, the overlap joint marginal part also can appear because of curtain coating or edge effect in the inward flange on edge layer (the outward flange on middle part layer), overlap joint marginal part covers to the curtain coating source portion on, avoid appearing the region of sinking at the contact site of middle part layer and edge layer, ensure that dressing layer surfacing, guarantee that the negative pole capacity of dressing layer optional position all satisfies the design demand in the thickness direction.

Optionally, the connecting portions of the central layer and the edge layer merge with each other and form a merged edge portion.

Through adopting above-mentioned technical scheme, when coating middle part layer and edge layer simultaneously, the outward flange on middle part layer contacts and fuses each other with the inward flange on edge layer and forms and fuses the marginal portion, and the edge layer pastes tight middle part layer, and the region of sinking can not appear in the position department of middle part layer to the transition of edge layer, and the negative pole capacity of dressing layer optional position all satisfies the design demand in the thickness direction.

Optionally, the current collector further comprises a blank portion arranged on the side, opposite to the main body portion, of the edge portion along the length direction, the blank portion is not covered by the dressing layer, and the edge portion is located between the blank portion and the main body portion.

Through adopting above-mentioned technical scheme, the thick liquids overflow when setting up blank portion and avoiding coating the marginal layer, and blank portion can also be used for placing utmost point ear.

The utility model provides an above-mentioned one or more technical scheme in the negative pole piece have one of following technological effect at least: because the unit area negative pole capacity of edge layer is higher than the unit area negative pole capacity of middle part layer, when the unit area negative pole capacity of middle part layer equals the design unit area negative pole capacity of negative pole piece, the negative pole capacity of edge layer has been improved in other words, even the thickness of the outward flange of edge layer reduces because of the thick liquids flows gradually, the negative pole capacity that also can ensure the edge layer is not less than the design negative pole capacity to can avoid the negative pole piece because the coating layer edge region is not enough because of the negative pole capacity that curtain coating or edge effect caused, reduce the utility model discloses the lithium risk of analyzing of negative pole piece improves the security performance when using.

The utility model discloses another technical scheme is: a lithium ion battery is provided, which comprises the negative pole piece.

The utility model discloses a lithium ion battery, owing to used foretell negative pole piece, lithium ion battery takes place to analyse the risk greatly reduced of lithium, and battery safety can promote, and life is longer.

Drawings

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

Fig. 1 is a front view of a negative electrode tab according to an embodiment of the present invention;

fig. 2 is a sectional view of a negative electrode plate according to another embodiment of the present invention;

fig. 3 is a cross-sectional view of a negative electrode plate according to another embodiment of the present invention;

fig. 4 is a sectional view of a negative electrode plate according to still another embodiment of the present invention.

Wherein, in the figures, the respective reference numerals:

10-a current collector; 11-a body portion; 12-an edge portion; 13-blank; 20-a dressing layer; 21-middle layer; 211-casting edge; 212-a fusion edge; 22-an edge layer; 221-overlapping edge portions; 222-casting the edge region.

Detailed Description

In order to make the technical problem, technical scheme and beneficial effect that the utility model will solve more clearly understand, it is right to combine fig. 1 ~ 4 and embodiment below the utility model discloses further detailed description proceeds. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It is to be understood that the terms "length," "width," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention. Furthermore, the terms "first", "second", etc. 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. The meaning of "plurality" is two or more unless specifically limited otherwise.

As shown in fig. 1-4, the utility model provides a negative pole piece, including the mass flow body 10 and cover in the dressing layer 20 on the mass flow body 10 surface, in this embodiment, the mass flow body 10 can be for copper foil, aluminium foil, functional coating paper tinsel, stainless steel foil, nickel foil, carbon paper etc. have the metal foil layer or the arbitrary one in the non-metallic film layer of conducting capacity, and the upper surface and the lower surface of the mass flow body 10 all cover dressing layer 20.

In one embodiment, the current collector 10 has a main body 11 located in the middle and edge portions 12 disposed on opposite sides of the main body 11 along the length direction, the dressing layer 20 includes a middle layer 21 and edge layers 22 disposed on opposite sides of the middle layer 21 along the length direction, the inner edges of the edge layers 22 are closely attached to the outer edges of the middle layer 21, and in this embodiment, "the edge layers 22 disposed on opposite sides of the middle layer 21" means: the edge layer 22 is closely butted against the central layer 21, or the material of the contact part between the edge layer 22 and the central layer 21 is fused, and the width of the fused part is not strictly limited. The middle layer 21 correspondingly covers the main body part 11, the edge layer 22 correspondingly covers the edge part 12, the negative electrode capacity per unit area of the edge layer 22 is higher than that of the middle layer 21, and the negative electrode capacity per unit area of the middle layer 21 is equal to the preset negative electrode capacity per unit area, wherein the negative electrode capacity per unit area refers to the capacity which can be provided by the negative electrode active material per unit area, and the preset negative electrode capacity per unit area refers to the negative electrode capacity per unit area which is required to be achieved after the negative electrode pole piece is molded.

The negative pole piece of the embodiment of the utility model divides the coating layer 20 into the middle layer 21 and the edge layer 22, the middle layer 21 corresponds to the main body part 11 covering the current collector 10, the edge layer 22 corresponds to the edge part 12 covering the current collector 10, because the unit area negative capacity of the edge layer 22 is higher than the unit area negative capacity of the middle layer 21, when the unit area negative capacity of the middle layer 21 is equal to the design unit area negative capacity of the negative pole piece, the negative pole capacity of the edge layer 22 is increased, thus, even if the thickness of the outer edge of the edge layer 22 is gradually reduced due to slurry flow, the negative pole capacity of the edge layer 22 is not lower than the design negative pole capacity, the lithium precipitation risk of the negative pole piece of the utility model can be avoided because the edge part 12 of the coating layer 20 is insufficient due to the negative pole capacity caused by flow casting or edge effect, the safety performance in use is improved.

It should be noted that, in the conventional lithium ion battery production process, a negative electrode plate is generally manufactured by a method of coating first and then cutting, that is, slurry is coated on a coiled current collector substrate first, and the current collector substrate coated with the slurry is cut in sections after the slurry coating is completed, so as to manufacture a single negative electrode plate. Thus, when slurry is coated, due to the influence of casting or edge effect, edge casting areas can appear at the edges of the two sides of the length direction of the current collector substrate and at the edges of the two ends along the width direction, and the casting edge areas at the two sides in the length direction still can exist on a single negative electrode plate after cutting, and the casting edge areas at the two ends in the width direction can not appear on the single negative electrode plate due to cutting, that is, for the negative electrode plate produced by using the production process of coating first and cutting second, the edge casting areas can only appear at the two sides in the length direction generally, therefore, for the embodiment, the edge parts 12 are reserved at the two sides of the length direction of the current collector 10, and the problem of lithium precipitation can be effectively solved by setting the edge layer 22 with higher negative electrode capacity per unit area to cover the edge parts 12 correspondingly.

In particular, for the production method of the coating slurry after cutting, the edge casting area may be present at the position of the peripheral edge of the current collector 10 due to the influence of casting or edge effect, and in this case, the edge portion 12 may be provided at the peripheral edge of the current collector 10, and the edge layer 22 may be provided at the peripheral edge of the coating layer 20.

In this embodiment, as shown in fig. 1, the central layer 21 and the edge layer 22 are coated with different dressings to ensure that the negative capacity per unit area of the edge layer 22 is greater than that of the central layer 21. In a particular fabrication process, the dressing used to apply the central layer 21 includes a first active substance, a first conductive agent, and a first adhesive, and the dressing used to apply the edge layer 22 includes a second active substance, a second conductive agent, and a second adhesive. The first active substance and the second active substance can be one or more of active substances such as artificial graphite, natural graphite, hard carbon, soft carbon, silicon-carbon composite material, silica compound, carbon microsphere intermediate phase, lithium titanate and the like, the first conductive agent and the second conductive agent can be one or more of conductive agents such as carbon black, carbon tubes, graphene, carbon fibers, conductive graphite and the like, and the first adhesive and the second adhesive can be one or more of adhesives such as polyacrylic acid, polyacrylate, polyacrylonitrile copolymer, polytetrafluoroethylene, polyvinylidene fluoride, styrene butadiene rubber, sodium carboxymethylcellulose and the like. After the materials are selected, the dressing of the middle layer 21 and the edge layer 22 can be obtained by stirring by a conventional stirring method.

In another embodiment of the present invention, as shown in fig. 1, the gram capacity of the active material in the edge layer 22 is higher than that of the active material in the middle layer 21, so that the negative electrode capacity per unit area of the edge layer 22 is higher than that of the middle layer 21 by selecting the active material with high gram capacity. Therefore, when different dressings are selected to coat the middle layer 21 and the edge layer 22, only active substances with different gram volumes need to be distinguished and selected, other materials such as the same conductive agent and adhesive can be selected, and the materials are more convenient to select. Where gram volume refers to the ratio of the amount of capacitance that can be released by the active material in the dressing layer 20 to the mass of the active material.

Specifically, in this embodiment, as shown in fig. 1, the dressing material of the middle layer 21 may be a composite of artificial graphite, conductive carbon black SP and carbon nanotubes CNTs, styrene butadiene rubber SBR and sodium carboxymethyl cellulose CMC, wherein the weight ratio of the artificial graphite, SP, CNTs, SBR and CMC may be 90-98: 0.5-3.0: 1.2-3.0: 0.5-2, specifically 93.6: 2: 1.5: 1.5: 1.4, or 95.3:1:0.2:2.3:1.2, etc.; the dressing material of the edge layer 22 can be selected from the compound of artificial graphite, conductive carbon black SP carbon tubes CNTs and graphene, styrene butadiene rubber SBR and sodium carboxymethyl cellulose CMC, wherein the weight ratio of the artificial graphite, SP, CNTs, graphene, SBR and CMC can also be 90-98: 0.5-3.0: 1.2-3.0: 0.5-2, for example, can be specifically 93.6: 2: 1.1: 0.4: 1.5: 1.4, etc.; specifically, the central layer 21 and the edge layer 22 can be designed within the same mixture ratio range, and it is only necessary to satisfy that the weight of the artificial graphite of the edge layer 22 is higher than that of the central layer 21, so as to ensure that the gram volume of the active material in the edge layer 22 is larger than that of the active material in the central layer 21.

Further, in the present embodiment, as shown in fig. 1, the gram capacity of the active material in the middle layer 21 is preferably 250mAh/g to 400mAh/g, such as 250mAh/g, 280mAh/g, 300mAh/g, 320mAh/g, 350mAh/g, 380mAh/g, or 400mAh/g, and the gram capacity of the active material in the edge layer 22 is preferably 300mAh/g to 450mAh/g, such as 300mAh/g, 320mAh/g, 350mAh/g, 380mAh/g, 400mAh/g, 420mAh/g, or 450 mAh/g. During design, on the basis that the gram volume of the active substances in the edge layer 22 is larger than that of the active substances in the middle layer 21, the active substances can be selected according to specific design requirements, different active substances are selected in the gram volume numerical range, the selection range of the active substances is narrowed, and the calculation difficulty is prevented from being increased excessively due to mass selection.

Of course, in some other embodiments, as shown in fig. 1, the active material in the central layer 21 and the active material in the edge layer 22 may also be active materials with other gram volume values, which is not limited herein.

In another embodiment of the present invention, as shown in fig. 1, the width of the edge layer 22 is 0.5mm to 50mm, that is, the distance between the outer edge of the edge layer 22 and the outer edge of the middle layer 21 is 0.5mm to 50mm, and the width range basically covers the width dimension of the region where the thickness of the traditional negative electrode plate gradually decreases due to the casting or the edge effect, so as to ensure that the width of the edge layer 22 is greater than or equal to the width of the region where the thickness of the dressing layer 20 on the traditional negative electrode plate gradually decreases due to the casting or the edge effect, and ensure that the setting of the edge layer 22 can offset the reduction of the negative electrode capacity due to the casting or the edge effect. In particular embodiments, the width of the edge layer 22 may be any value from 0.5mm to 50 mm.

Further, in the present embodiment, as shown in fig. 1, the width of the edge layer 22 is preferably 2mm to 15mm, and the provision of the edge layer 22 within the width range can ensure that most of the negative electrode tab does not have a lithium deposition phenomenon at the edge, specifically, the width of the edge layer 22 may be 2mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 13mm, or 15mm, etc.

In another embodiment of the utility model, as shown in fig. 2 ~ 4, the height that the edge layer 22 deviates from the surface of edge portion 12 is not higher than the height that middle part layer 21 deviates from the surface of main part 11, the setting height of edge layer 22 is equal to or is less than the setting height of middle part layer 21 promptly, that is to say, when the mass flow body 10 surfacing, the thickness of the dressing that covers on the edge portion 12 equals or is less than the thickness of the dressing that covers on the main part 11, so, in order to avoid leading to negative pole piece edge bulging because of edge layer 22 thickness sets up too high, avoid the negative pole piece fracture to fall whitewashed. Specifically, in this embodiment, the specific thicknesses of the side insulating layer 22 and the middle layer 21 do not need to be limited, and the specific setting may be performed according to the gram volume of the active material in the dressing, the negative electrode capacity required by the negative electrode sheet, and the NP ratio between the negative electrode sheet and the positive electrode sheet in the lithium battery manufacturing process.

In another embodiment of the invention, as shown in fig. 2 and 3, the outer edge of the middle layer 21 extends towards the edge layer 22 with a casting edge 211 and the inner edge of the edge layer 22 extends towards the middle layer 21 with a lapping edge 221, or the inner edge of the edge layer 22 extends towards the middle layer 21 with a casting edge 211 and the outer edge of the middle layer 21 extends towards the edge layer 22 with a lapping edge 221; the overlapping edge 221 covers the casting edge 211. Specifically, in the actual manufacturing process, when the middle layer 21 is coated first, the outer edge of the middle layer 21 may have the casting edge 211 due to the casting or edge effect, and thus when the edge layer 22 is coated again, the inner edge of the edge layer 22 may have the overlapping edge 221 covering the casting edge 211 due to the casting or edge effect, as shown in fig. 2; alternatively, when the edge layer 22 is coated first, the inner edge of the edge layer 22 may extend toward the middle layer 21 to form the casting edge 211 due to casting or edge effect, and when the middle layer 21 is coated again, the outer edge of the middle layer 21 may extend toward the edge layer 22 to form the overlapping edge 221 covering the casting edge 211 due to casting or edge effect, as shown in fig. 3. Thus, when the middle layer 21 and the edge layer 22 are not coated simultaneously, the lapping edge part 221 is lapped and covered on the casting edge part 211 due to casting or edge effect, so that a sinking region is avoided at the contact part of the middle layer 21 and the edge layer 22, the surface smoothness of the dressing layer 20 departing from the current collector 10 is ensured, and the negative electrode capacity of any position of the dressing layer 20 in the thickness direction can meet the design requirement.

Further, in the embodiment, as shown in fig. 2 and 3, the surface of the casting lip 211 formed by the first applied middle layer 21 or edge layer 22 is convex arc-shaped with a convex center, and correspondingly, the surface of the overlapping lip 221 formed by the second applied edge layer 22 or edge layer 21 is concave arc-shaped with a concave center, due to the flow characteristics of the dressing. The central bulge is a bulge formed along the fashion direction of the dressing, and the central concave is a concave formed back to the fashion direction of the dressing, and the central concave is a left bulge or a right bulge or a concave with the horizontal direction in fig. 2 or fig. 3 as a reference.

In another embodiment of the present invention, as shown in fig. 4, unlike the above-mentioned embodiment, the connecting portions of the middle layer 21 and the edge layer 22 are fused with each other to form a fused edge portion 212. Thus, when the middle layer 21 and the edge layer 22 are coated simultaneously, the outer edge of the middle layer 21 contacts with the inner edge of the edge layer 22 and is fused with each other to form a fused edge 212, the edge layer 22 is attached to the middle layer 21, no sinking region is generated at the transition position of the middle layer 21 to the edge layer 22, and the cathode capacity at any position of the dressing layer 20 in the thickness direction meets the design requirement.

In the above two embodiments, as shown in fig. 2, fig. 3 and fig. 4, the casting edge region 222 appears at the outer edge of the edge layer 22 away from the middle layer 21 due to casting or edge effect, and since the negative electrode capacity per unit area of the edge layer 22 is larger than the designed negative electrode capacity per unit area of the negative electrode sheet of this embodiment, the occurrence of the casting edge region 222 does not cause the reduction of the negative electrode capacity of the sheet.

In another embodiment of the present invention, as shown in fig. 1 and 4, the current collector 10 further includes a blank portion 13 disposed on the edge portion 12 along the length direction and facing away from the main body portion 11, the edge portion 12 is disposed between the blank portion 13 and the main body portion 11, the blank portion 13 is not coated with the coating layer 20, so that the slurry overflows when the edge layer 22 is coated, the reduction of the negative electrode capacity caused by slurry overflow is avoided, and the blank portion 13 can also be used for placing the tab.

Another embodiment of the utility model provides a lithium ion battery (not shown), including foretell negative pole piece, this lithium ion battery is owing to used foretell negative pole piece, and lithium ion battery takes place to analyse the risk greatly reduced of lithium, and battery safety can promotes, and life is longer.

Specifically, in the lithium ion battery of this embodiment, except that the negative pole piece adopts the utility model discloses the negative pole piece that above-mentioned embodiment provided, other all can be but not limited to use current material like positive pole piece, utmost point ear, diaphragm, electrolyte and shell etc. specifically select can satisfy the material of battery electrical property requirement can. And, also can but not be limited to the equipment process to lithium ion battery and adopt current process, will according to current mode the utility model discloses after negative pole piece, diaphragm, positive pole piece and utmost point ear etc. of above-mentioned embodiment are stacked gradually and are convoluteed into electric core, put into battery case, can obtain finished product lithium ion battery after flow such as toasting, notes liquid, seal, formation, ageing, partial volume.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. The negative pole piece is characterized in that the current collector comprises a main body part positioned in the middle and edge parts arranged on two opposite sides of the main body part along the length direction, the dressing layer comprises a middle layer and edge layers arranged on two opposite sides of the middle layer along the length direction, the middle layer correspondingly covers the main body part, the edge layers correspondingly cover the edge parts, and the negative capacity per unit area of the edge layers is higher than that of the middle layer.

2. The negative electrode tab of claim 1, wherein: the width of the edge layer is 0.5 mm-50 mm.

3. The negative electrode tab of claim 2, wherein: the width of the edge layer is 2 mm-15 mm.

4. The negative electrode tab of claim 1, wherein: the height of the surface of the edge layer facing away from the edge portion is not higher than the height of the surface of the middle layer facing away from the main body portion.

5. The negative electrode plate as claimed in any one of claims 1 to 4, wherein: the outer edge of the middle layer extends towards the edge layer to form a casting edge, and the inner edge of the edge layer extends towards the middle layer to form a lapping edge;

or the inner edge of the edge layer extends towards the middle layer to form a casting edge part, and the outer edge of the middle layer extends towards the edge layer to form a lap edge part;

the lap edge portion covers the casting edge portion.

6. The negative electrode plate as claimed in any one of claims 1 to 4, wherein: the middle layer and the connecting part of the edge layer are mutually fused to form a fused edge part.

7. The negative electrode plate as claimed in any one of claims 1 to 4, wherein: the mass flow body still includes along length direction set up in the edge part dorsad the blank portion of main part one side, the edge part is located blank portion with between the main part.

8. A lithium ion battery, characterized by comprising the negative electrode sheet of any one of claims 1 to 7.