CN114156488A

CN114156488A - Pole piece, preparation method thereof and battery

Info

Publication number: CN114156488A
Application number: CN202111434767.1A
Authority: CN
Inventors: 翟艳云; 彭冲
Original assignee: Zhuhai Cosmx Battery Co Ltd
Current assignee: Zhuhai Cosmx Battery Co Ltd
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2022-03-08

Abstract

The invention provides a pole piece, a preparation method thereof and a battery. The pole piece provided by the invention comprises a current collector, an active substance layer and a pole lug sheet, wherein the current collector comprises a first conducting layer, a substrate layer and a second conducting layer which are sequentially stacked; the current collector is divided into a first area and a second area along the width direction of the current collector, and the active substance layer covers the two side surfaces of the current collector in the first area; at least one passage is formed in the second area, the passage penetrates through the two side surfaces of the current collector in the thickness direction, and the tab piece penetrates through the passage and is connected to the surface of the first conducting layer and the surface of the second conducting layer. The pole piece provided by the invention can reduce the weight of the battery, improve the energy density of the battery and improve the safety performance of the battery.

Description

Pole piece, preparation method thereof and battery

Technical Field

The invention relates to the technical field of batteries, in particular to a pole piece, a preparation method of the pole piece and a battery.

Background

Since the first commercial lithium ion battery was released by sony corporation in 1991, lithium ion batteries have been widely used in the fields of consumer electronics, electric vehicles, energy storage, and the like.

Conventional lithium ion batteries use aluminum foil as the positive current collector and copper foil as the negative current collector. In order to increase the energy density of the battery, part of the aluminum foil and part of the copper foil can be replaced by lighter polymer materials. For example, aluminum-polymer-aluminum or copper-polymer-copper is used. The surface density of the current collector with the sandwich structure is smaller, so that the weight of the battery can be reduced, and the energy density can be improved; meanwhile, when the battery is short-circuited, the battery is heated to a certain temperature by the current collector with the structure, the polymer layer in the battery is easy to shrink when being heated, so that the short circuit is avoided, combustion or explosion is not easy to occur, and the current collector has better safety than the conventional copper foil and aluminum foil.

However, since the polymer layer of the current collector having the sandwich structure is not conductive, the tab is welded to one surface of the current collector and the other surface is not conductive, and thus, the battery pole piece needs to be redesigned.

Disclosure of Invention

The invention provides a pole piece, a preparation method thereof and a battery, and aims to solve the problem that two side surfaces of a current collector with a sandwich structure in the background art cannot conduct electricity.

In order to achieve the above purpose, the invention provides the following technical scheme:

in one aspect, the invention provides a pole piece, which comprises a current collector, an active material layer and a pole lug, wherein the current collector comprises a first conducting layer, a base layer and a second conducting layer which are sequentially stacked;

the current collector is divided into a first area and a second area along the width direction of the current collector, and the active substance layer covers the two side surfaces of the current collector in the first area; at least one passage is formed in the second area, the passage penetrates through the two side surfaces of the current collector in the thickness direction, and the tab piece penetrates through the passage and is connected to the surface of the first conducting layer and the surface of the second conducting layer.

In one possible embodiment, the number of the channels is one, and the tab piece comprises a first section and a second section, wherein the first section is connected to the first conductive layer, and the second section passes through the channels and is connected to the second conductive layer;

the first section and the second section are located on two sides of the passage along the length direction of the current collector, or the first section and the second section are located on the same side of the passage.

In one possible embodiment, the number of channels is greater than or equal to two, each channel being spaced apart along the length of the current collector, and the tab pieces passing through each channel in sequence.

In one possible embodiment, the passage is a conduction groove, and a notch of the conduction groove is located on the side surface of the current collector.

In one possible embodiment, the tab sheet comprises a tab main body and a plurality of tab branches connected to the tab main body, wherein the tab branches are distributed at intervals along the length direction of the tab main body;

wherein, utmost point ear main part is connected on the surface of mass flow body, and utmost point ear branch stretches out outside the width direction of mass flow body.

In one possible embodiment, the ratio of the extension length of the tab branches to the width of the tab main body in the width direction of the current collector ranges from 0.5 to 5.

In one possible embodiment, the surface of the first conductive layer and the surface of the second conductive layer are provided with welding areas, and the pole lug pieces are connected with the first conductive layer and the second conductive layer in the welding areas in a welding mode.

In one possible embodiment, the pole piece further comprises a protective layer covering at least a portion of the pole tab located within the weld region.

In one possible embodiment, the first and second conductive layers are metal layers and the base layer is a polymer layer.

In another aspect, the present invention provides a battery comprising a pole piece as described above.

According to the pole piece and the preparation method thereof as well as the battery, the pole piece comprises the current collector, the current collector comprises the first conducting layer, the base layer and the second conducting layer which are sequentially stacked, and the light base layer is adopted to replace part of the conducting layers, so that the surface density of the current collector is smaller, the weight of the battery is reduced, and the energy density of the battery is improved; meanwhile, when the battery is subjected to mechanical abuse to cause short circuit, the battery is heated to a certain temperature, the substrate layer is easy to deform and shrink to damage the current collector and cut off a current loop, so that the battery is not easy to burn or explode, and the safety performance of the battery can be improved. The electrode lug pieces are connected to the second area of the current collector, which is not covered with the active material layer, penetrate through the passages formed in the second area of the current collector, and are partially attached to the surface of the first conducting layer and partially attached to the surface of the second conducting layer so as to conduct the first conducting layer and the second conducting layer on two sides of the current collector.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced, and it is obvious that the drawings in the following description are some embodiments of the present invention. For a person skilled in the art, without inventive effort, further figures can be obtained from these figures.

Fig. 1 is a top view of a pole piece according to a first embodiment of the present invention;

fig. 2 is a schematic structural view of the current collector in fig. 1;

FIG. 3 is a block diagram of the pole piece of FIG. 1 with the pole tab removed;

fig. 4a is a layout structure diagram of tab pieces according to an embodiment of the present invention;

fig. 4b is another layout structure diagram of a tab sheet according to an embodiment of the present invention;

FIG. 4c is a third layout structure of a pole tab according to an embodiment of the present invention;

FIG. 5a is a cross-sectional view taken at A-A of FIG. 1;

FIG. 5B is a cross-sectional view taken at B-B of FIG. 1;

fig. 6 is a schematic flow chart of a manufacturing method of a pole piece according to a second embodiment of the present invention;

fig. 7 is a schematic structural diagram of a cell formed by winding a pole piece according to a second embodiment of the present invention.

Description of reference numerals:

100-pole piece; 200-a membrane;

1-current collector; 2-an active material layer; 3-pole ear; 4-a protective layer;

1 a-a first conductive layer; 1 b-a substrate layer; 1 c-a second conductive layer; 11-a first region; 12-a second region; 13-a channel; 13 a-a conducting slot; 14-a welding zone; 31-a tab body; 32-pole ear branch; 3 a-first stage; 3 b-second segment.

Detailed Description

Conventional lithium ion batteries use a metal sheet as a positive electrode current collector or a negative electrode current collector, for example, an aluminum foil as a positive electrode current collector and a copper foil as a negative electrode current collector. The current collector with the structure has higher surface density, so that the weight of the battery is higher and the energy density is lower.

In order to increase the energy density of the lithium ion battery, a sandwich structure of a metal layer, a polymer layer and a metal layer can be used as a current collector. The polymer layer is used for replacing part of the metal layer, and the density of the polymer layer is low, so that the density of the current collector can be reduced, the weight of the battery is reduced, and the energy density of the battery is improved.

Meanwhile, the polymer layer is easy to change the shape of the polymer layer due to temperature change, so that when the battery is short-circuited due to mechanical abuse, the battery is heated to a certain temperature, the current collector of the sandwich structure is damaged, a current path in the battery can be cut off, accidents such as combustion or explosion of the battery cannot be caused, and the safety performance of the battery can be improved.

However, in the current collector with the sandwich structure, the middle polymer layer is not conductive, so that a tab is welded on one side surface of the current collector and cannot be conducted with the other side surface of the current collector, and a tab welding mode needs to be redesigned.

In order to solve the technical problems, the invention provides a pole piece, a preparation method thereof and a battery. And the pole lug of the pole piece is provided with a plurality of pole lug branches extending outwards, so that the resistance of the pole piece can be reduced, and the high-rate performance of the battery is improved.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example one

Fig. 1 is a top view of a pole piece according to a first embodiment of the present invention; fig. 2 is a schematic structural view of the current collector in fig. 1; FIG. 3 is a block diagram of the pole piece of FIG. 1 with the pole tab removed; FIG. 4a is a block diagram of a layout of pole tabs according to an embodiment of the present invention; fig. 4b is another layout structure diagram of a tab sheet according to an embodiment of the present invention; FIG. 4c is a third layout structure diagram of pole tabs provided in accordance with an embodiment of the present invention; FIG. 5a is a cross-sectional view taken at A-A of FIG. 1; fig. 5B is a cross-sectional view at B-B in fig. 1.

As shown in fig. 1, the present embodiment provides a pole piece 100, and the pole piece 100 can be applied to a battery. Specifically, the pole piece 100 may be a positive pole piece or a negative pole piece, and the positive pole piece, the negative pole piece and the diaphragm together form a battery core of the battery.

The following description will be given by taking the application of the pole piece 100 in a battery as an example, and will not be repeated.

As shown in fig. 1, the pole piece 100 includes a current collector 1, an active material layer 2, and a tab piece 3. Wherein the current collector 1 serves as a basic carrier of the pole piece 100 for collecting current. Specifically, in the width direction of the current collector 1, i.e., the Y direction shown in fig. 1, the current collector 1 is divided into a first region 11 and a second region 12, the active material layer 2 is coated on the surface of the current collector 1 located in the first region 11, and the tab sheet 3 is attached to the surface of the current collector 1 located in the second region 12.

The active substance layer 2 contains an active substance, the active substance is used for generating current, the current generated by the active substance is collected on the current collector 1, the current is transmitted to the pole lug piece 3 from the current collector 1, the pole lug piece 3 is electrically connected with an external circuit through a switching pole lug, and the current transmission between the pole piece 100 and the external circuit is realized through the pole lug piece 3.

Taking a lithium ion battery as an example, in the discharging process of the battery, the current in the current collector 1 is transmitted to the external circuit through the pole lug 3, and in the charging process of the battery, the current in the external circuit is transmitted to the current collector 1 through the pole lug 3.

In correspondence with the positive and negative electrodes of the battery, if the electrode sheet 100 is a positive electrode sheet, the active material contained in the active material layer 2 coated on the surface of the current collector 1 is a positive electrode active material, and the tab sheet 3 connected to the current collector 1 is a positive electrode tab; when the electrode sheet 100 is a negative electrode sheet, the active material contained in the active material layer 2 coated on the surface of the current collector 1 is a negative electrode active material, and the tab sheet 3 connected to the current collector 1 is a negative electrode tab.

In order to reduce the weight of the battery and increase the energy density of the battery, as shown in fig. 2, in the present embodiment, the current collector 1 is composed of a first conductive layer 1a, a base layer 1b, and a second conductive layer 1c, which are sequentially stacked. By providing current collector 1 in a sandwich structure in which first conductive layer 1a and second conductive layer 1c sandwich substrate layer 1b, substrate layer 1b may be used instead of a portion of the conductive layer, and substrate layer 1b may be, for example, a polymer layer, which is generally lower in density and weight than the conductive layer. Therefore, the current collector 1 with the sandwich structure has lower density, the weight of the battery can be reduced, and the energy density of the battery is improved.

Meanwhile, the polymer layer may shrink at a high temperature to change its shape, and further, may affect the shapes of the first conductive layer 1a and the second conductive layer 1c attached thereto. Therefore, when the battery is short-circuited, the current collector 1 with the structure is heated to a certain temperature, the structure of the current collector 1 is easily damaged, and then a current path between the current collector 1 and other conductive parts can be cut off, so that the battery cannot be burnt or exploded, and the safety performance of the battery can be improved.

To further reduce the weight of the current collector 1 and increase the battery energy, in some embodiments, pores may be reserved in the matrix layer 1b, and the pores in the matrix layer 1b may also be communicated to the first conductive layer 1a and the second conductive layer 1 c. In addition, a conductive material can be filled in the pores of the substrate layer 1b to conduct the first conductive layer 1a and the second conductive layer 1c, so that the conductivity of the current collector 1 is improved.

Specifically, the first conductive layer 1a and the second conductive layer 1c may be metal layers or alloy layers. The material constituting the first conductive layer 1a and the second conductive layer 1c includes, but is not limited to, aluminum, copper, nickel, silver, gold, iron, and the like. The first conductive layer 1a and the second conductive layer 1c may be made of the same metal material or alloy material, or the first conductive layer 1a and the second conductive layer 1c may have different compositions.

The substrate layer 1b may be a polymer layer, and the polymer constituting the substrate layer 1b includes, but is not limited to, Polyethylene terephthalate (PET), Polypropylene (PP), Polyethylene (PE), Polyimide (PI), Polyether ketone (PEK), and Polyphenylene Sulfide (PPs).

In other embodiments, a transition layer (not shown) may be disposed between the first conductive layer 1a and the substrate layer 1b and between the second conductive layer 1c and the substrate layer 1b, and the transition layer is used to improve the connection strength between the first conductive layer 1a and the substrate layer 1b and between the second conductive layer 1c and the substrate layer 1b, so as to prevent the first conductive layer 1a and the second conductive layer 1c from falling off the substrate layer 1 b.

Exemplary materials comprising the transition layer include, but are not limited to, aluminum oxide, titanium oxide, magnesium oxide, and the like.

In the present embodiment, both side surfaces of the current collector 1 in the first region 11 may be covered with the active material layer 2, that is, both the outer surface of the first conductive layer 1a and the outer surface of the second conductive layer 1c are covered with the active material layer 2. So, can make active material and mass flow body 1 fully contact, have great area of contact between active material layer 2 and the mass flow body 1 to the mass flow body 1 collects the electric current that active material layer 2 produced, and then, forms great electric current through the mass flow body 1 and exports outward.

It should be understood that the outer surface of the first conductive layer 1a as referred to herein means the surface of the first conductive layer 1a facing away from the base layer 1b, and similarly, the outer surface of the second conductive layer 1c means the surface of the second conductive layer 1c facing away from the base layer 1 b.

Illustratively, the active material layer 2 generally includes an active material, a conductive agent, and a binder.

In a specific application, in the case where the electrode sheet 100 is a positive electrode sheet, the active material may be a positive electrode active material. The positive active material comprises at least one of Lithium Cobaltate (LCO), a nickel-cobalt-manganese ternary material (NCM), a nickel-cobalt-aluminum ternary material (NCA), a nickel-cobalt-manganese-aluminum quaternary material (NCMA), lithium iron phosphate (LFP), Lithium Manganese Phosphate (LMP), Lithium Vanadium Phosphate (LVP), Lithium Manganate (LMO) and a lithium-rich manganese base.

In the case where the pole piece 100 is a negative pole piece, the active material may be a negative active material. The negative active substance comprises at least one of graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon materials, silica materials, silicon carbon materials and lithium titanate.

The conductive agent comprises at least one of conductive carbon black, carbon nano tubes, conductive graphite and graphene.

The adhesive comprises at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene butadiene rubber.

In practical applications, in order to maintain the battery capacity, the active material layer 2 should have enough coverage area on the current collector 1 to allow the active material layer 2 to generate enough current, while the second area 12 of the current collector 1 is only used for connecting the tab piece 3 with smaller structural size, so that the surface area of the first area 11 of the current collector 1 for covering the active material layer 2 is generally larger, and the surface area of the second area 12 for connecting the tab piece 3 is smaller.

In the present embodiment, the ratio of the width of the second region 12 to the width of the first region 11 of the current collector 1 in the width direction of the current collector 1, i.e., the Y direction shown in fig. 1, is between 0 and 1, and for example, the ratio may be between 0.1 and 0.4.

Referring to fig. 1 and 2, in the present embodiment, since the current collector 1 is a sandwich structure, the first conductive layer 1a and the second conductive layer 1c located on the upper and lower sides of the current collector 1 can conduct electricity, however, the substrate layer 1b sandwiched between the first conductive layer 1a and the second conductive layer 1c is generally not conductive. In contrast, the tab piece 3 connected to the second region 12 of the current collector 1 may be used to conduct the first conductive layer 1a and the conductive layers on two sides of the current collector 1 by using the tab piece 3, so as to realize the function of generating and transmitting current by the electrode piece 100, on the basis of transmitting current with an external circuit.

In order to connect the first conductive layer 1a and the second conductive layer 1c through the electrode tab 3, referring to fig. 3, in the present embodiment, a passage 13 is formed in the second region 12 of the current collector 1, and the passage 13 is formed along the thickness direction of the current collector 1, passes through the first conductive layer 1a, the base layer 1b, and the second conductive layer 1c, and penetrates through both side surfaces of the current collector 1 in the thickness direction.

As shown in fig. 1, when the electrode tab 3 is connected to the surface of the current collector 1, the electrode tab 3 is made to pass through the passage 13 provided in the second region 12, so that the part of the electrode tab 3 may be located on one side surface of the base layer 1b, the part of the electrode tab 3 may be located on the other side surface of the base layer 1b, and by making the electrode tab 3 pass through the passage 13 and extend along the two side surfaces of the current collector 1 in the second region 12, the parts of the electrode tab 3 respectively located on the two side surfaces of the current collector 1 are both attached to the two side surfaces of the current collector 1, so that the current collector 1 is turned on by the electrode tab 3.

Specifically, a partial section of the tab piece 3 is attached to the outer surface of the first conductive layer 1a, and the tab piece 3 passes through the channel 13, so that a partial section thereof is attached to the outer surface of the second conductive layer 1c, and thus the first conductive layer 1a and the second conductive layer 1c are connected by the tab piece 3 to conduct the first conductive layer 1a and the second conductive layer 1 c.

As an embodiment, only one passage 13 may be opened in the second region 12 of the current collector 1, a portion of the tab piece 3 is connected to the outer surface of the first conductive layer 1a, and another portion of the tab piece 3 is connected to the outer surface of the second conductive layer 1c through the passage 13. In this regard, as shown in fig. 4a and 4b, the tab 3 includes a first section 3a and a second section 3b, for example, the first section 3a of the tab 3 may be attached to one side surface of the current collector 1 (e.g., the outer surface of the first conductive layer 1 a), and the second section 3b of the tab 3 is attached to the other side surface of the current collector 1 (e.g., the outer surface of the second conductive layer 1 c) after the tab 3 passes through the passage 13.

As shown in fig. 4a, after the tab piece 3 passes through the channel 13, the second section 3b thereof may continue to extend in the original direction, and at this time, the second section 3b and the first section 3a of the tab piece 3 are respectively located at both sides of the channel 13. Taking the direction shown in fig. 4a as an example, along the length direction of the current collector 1, the first section 3a of the tab 3 extends from the right side of the current collector 1 to the left side, and after the tab 3 passes through the channel 13, the second section 3b of the tab 3 continues to extend in the direction of the left side of the current collector 1, so that the first section 3a and the second section 3b of the tab 3 are respectively located at two sides of the channel 13.

Alternatively, as shown in fig. 4b, after the tab sheet 3 passes through the channel 13, the second section 3b thereof may be extended in a reverse direction, in which case the second section 3b and the first section 3a of the tab sheet 3 are located on the same side of the channel 13. Taking the direction shown in fig. 4b as an example, along the length direction of the current collector 1, the first section 3a of the pole tab 3 extends from the right side of the current collector 1 to the left side, and after the pole tab 3 passes through the channel 13, the second section 3b thereof extends to the right side of the current collector 1 in a reverse direction, so that the first section 3a and the second section 3b of the pole tab 3 are both located at the right side of the channel 13.

As shown in fig. 4c, as another embodiment, a plurality of passages 13 may be opened in the second region 12 of the current collector 1, that is, the number of passages 13 opened in the second region 12 of the current collector 1 is greater than or equal to 2, wherein each passage 13 may be spaced along the length direction of the current collector 1, and the tab pieces 3 sequentially pass through each passage 13.

In practical applications, in order to ensure the strength of the second region 12 of the current collector 1, the number of the passages 13 and the volume occupied by all the passages 13 should be controlled within a reasonable range, and for example, the ratio of the sum of the cross-sectional areas of all the passages 13 to the area of the second region 12 of the current collector 1 may be in a range of 0.01 to 0.5. In this way, the volume occupied by the passages 13 does not exceed half the volume of the second region 12 of the collector 1, ensuring the stability of the second region 12 of the collector 1.

For example, the ratio of the sum of the cross-sectional areas of all the passages 13 to the area of the second region 12 of the current collector 1 may be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, etc.

It should be understood that, along the length direction of the current collector 1, since the tab pieces 3 need to sequentially pass through the respective passages 13, the tab pieces 3 extend in the same direction before the tab pieces 3 pass through the last passage 13 in the extending direction of the tab pieces 3, and after the tab pieces 3 pass through the last passage 13 from one side surface to the other side surface of the current collector 1, the tab pieces 3 may continue to extend in the original direction, or the tab pieces 3 may extend in the reverse direction.

In addition, as shown in fig. 1, in order to achieve the electrical connection of the pole piece 100 with the external circuit, in the present embodiment, in the width direction of the current collector 1, i.e., the Y direction shown in fig. 1, the tab piece 3 has a portion protruding out of the current collector 1 to be electrically connected with the external circuit through the portion of the tab piece 3 protruding out of the current collector 1.

Specifically, the tab piece 3 includes a tab main body 31 and a tab branch 32 connected to the tab main body 31. The tab main body 31 is connected to the surface of the current collector 1, the tab branch 32 extends out of the current collector 1, and the tab branch 32 is electrically connected to an external circuit through a switching tab, so as to realize the electrical connection between the pole piece 100 and the external circuit.

The tab main body 31 may be arranged in a length direction of the current collector 1, that is, an extending direction of the tab main body 31 is a length direction of the current collector 1, that is, an X direction shown in fig. 1. The tab main body 31 is located in the coverage of the second area 12 of the current collector 1, and the tab piece 3 is connected to the current collector 1 by connecting the tab main body 31 to the surface of the current collector 1 in the second area 12.

In the extending direction of the tab main body 31, i.e., the X direction shown in fig. 1, a tab branch 32 is connected to a side edge of the tab main body 31 on the side away from the second region 12, the tab branch 32 protruding out of the width direction of the current collector 1. Illustratively, the tab branches 32 may extend in the width direction of the current collector 1, and the tab branches 32 may be vertically connected to the tab main body 31, for example, the tab main body 31 extends in the length direction of the current collector 1.

In addition, with the rapid development of electronic devices, people have made higher requirements on the high-rate electrical performance of lithium ion batteries, and in order to improve the high-rate performance of batteries, in this embodiment, the tab main body 31 may be connected with a plurality of tab branches 32, and each tab branch 32 may be electrically connected to an external circuit through an external tab.

So, when transmitting electric current between pole piece 100 and the external circuit, the electric current can flow through each utmost point ear branch 32, and current channel 13 is more, like this, can effectively reduce pole piece 100's resistance, increases pole piece 100's electric current for the charging speed of battery promotes the high rate performance of battery.

For example, a plurality of tab branches 32 may be distributed at intervals along the length direction of the tab body 31, each tab branch 32 extends out of the current collector 1 along the width direction of the current collector 1, each tab branch 32 is electrically connected with an external circuit, a path is formed between each tab branch 32 and the external circuit through a through tab, and a current of the external circuit is introduced into the current collector 1, or a current generated by the current collector 1 is led out to the external circuit.

In order to ensure that the tab branch 32 has a sufficient extension length so that the tab branch 32 is electrically connected to an external circuit through a relay tab, as an embodiment, the ratio of the extension length of the tab branch 32 to the width of the tab main body 31 may range from 0.5 to 5.

Taking the example that the tab main body 31 extends in the longitudinal direction of the current collector 1 and the tab branch 32 extends in the width direction of the current collector 1, the extension direction of the tab branch 32 and the width direction of the tab main body 31 are both the width direction of the current collector 1, that is, the extension direction of the tab branch 32 and the width direction of the tab main body 31 are both the Y direction shown in fig. 1. That is, the ratio of the dimension L1 of the tab branch 32 to the dimension L2 of the tab main body 31 in the width direction of the current collector 1 is in the range of 0.5 to 5. Illustratively, the ratio of the dimension L1 of the tab branch 32 to the dimension L2 of the tab main body 31 ranges from 1 to 2, for example, the ratio of L1/L2 is 1.2, 1.4, 1.5, 1.6 or 1.8.

Since the tab piece 3 has the tab branch 32 extending out of the current collector 1, in order to facilitate the tab piece 3 to pass through the passage 13 formed in the second region 12 of the current collector 1, as shown in fig. 3, in the present embodiment, the passage 13 may be provided in the form of a conduction groove 13a, a notch of the conduction groove 13a is located on a side surface of the current collector 1, that is, in the thickness direction of the current collector 1, the passage 13 communicates with a side surface of the current collector 1, and a side surface of the passage 13 facing the side surface of the current collector 1 is open.

When the tab piece 3 is inserted into the conduction groove 13a, the tab branch 32 of the tab piece 3 can be inserted into the notch of the conduction groove 13a and extend out of the width direction of the current collector 1, so that the tab branch 32 can move smoothly in the conduction groove 13 a.

It can be understood that, since the conduction groove 13a is opened in the second region 12 of the current collector 1, the conduction groove 13a communicates with the side of the current collector 1, which means that the conduction groove 13a corresponds to the side of the second region 12 of the current collector 1, that is, the notch of the conduction groove 13a is located on the side of the current collector 1 corresponding to the side of the second region 12.

In other embodiments, the passages 13 opened in the second region 12 of the current collector 1 may also be in the form of communication holes, that is, the passages 13 are communication holes penetrating through both side surfaces of the current collector 1, and the communication holes are enclosed in the range covered by the second region 12 of the current collector 1. In this case, in order to facilitate the insertion of the tab piece 3 into the communication hole, the tab branches 32 of the tab piece 3 may be collectively disposed in a certain section of the tab piece 3, and the section does not pass through the communication hole when the tab piece 3 is inserted.

For example, taking the first section 3a and the second section 3b of the tab piece 3 shown in fig. 4a or fig. 4b as examples, which are respectively located on the two side surfaces of the current collector 1, the tab branches 32 may be centrally located on the first section 3a or the second section 3b of the tab piece 3.

In addition, in order to avoid the influence of the conduction groove 13a on the active material layer 2 coated on the surface of the current collector 1 in the first region 11, the edge of the conduction groove 13a close to the first region 11 and the boundary between the first region 11 and the second region 12 should have a pitch, that is, the size of the conduction groove 13a is smaller than the width of the second region 12 of the current collector 1 in the width direction of the current collector 1.

Illustratively, as shown in fig. 3, the distance from the edge of the conduction groove 13a close to the first region 11 to the boundary of the first region 11 and the second region 12 is L3, the width of the second region 12 of the current collector 1 is L4, the ratio of L3/L4 ranges from 0 to 1, and the ratio of L3/L4 ranges from 0.05 to 0.5, for example, the ratio of L3/L4 ranges from 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, and the like.

It should be noted that the present embodiment does not limit the specific shape and size of the channel 13, for example, the cross-sectional shape of the channel 13 may be designed substantially in a rectangular shape, a circular shape, a polygonal shape, an elliptical shape, and the like. In addition, in the case that the plurality of passages 13 are provided on the current collector 1, the shapes and sizes of the plurality of passages 13 may be completely or partially identical, or the shapes and sizes of the passages 13 are different, which is not limited in this embodiment.

As shown in fig. 1, in practical application, the tab piece 3 may be connected to the surface of the current collector 1 by welding. Wherein, corresponding to the sections of the tab sheet 3 connected to the two side surfaces of the current collector 1, the two side surfaces of the current collector 1 are both provided with welding areas 14, that is, the outer surface of the first conductive layer 1a and the outer surface of the second conductive layer 1c are both provided with welding areas 14, and each section of the tab sheet 3 is welded in the corresponding welding area 14.

Taking the example of fig. 1 where the first section 3a of the pole tab 3 is connected to one side surface of the current collector 1 (e.g., the outer surface of the first conductive layer 1 a), and the second section 3b is connected to the other side surface of the current collector 1 (e.g., the outer surface of the second conductive layer 1 c) through the passage 13, as shown in fig. 5a, the first section 3a of the pole tab 3 is welded to one side surface of the current collector 1, e.g., the first section 3a of the pole tab 3 is welded to the outer surface of the first conductive layer 1a in the welding area 14, and as shown in fig. 5b, the second section 3b of the pole tab 3 is welded to the other side surface of the current collector 1, e.g., the second section 3b of the pole tab 3 is welded to the welding area 14 of the outer surface of the second conductive layer 1 c.

As shown in fig. 1 and 2, since the tab 3 penetrates the current collector 1 at the position of the passage 13, the welding areas 14 disposed on both side surfaces of the current collector 1 in the second area 12 generally extend to be close to the passage 13 with a space from the passage 13. Illustratively, the distance between the welding area 14 and the edge of the passage 13 can be more than or equal to 1mm, so as to avoid the fracture of the current collector caused by the influence on the passage 13 during welding.

In addition, in the width direction of the current collector 1, the distance between the welding area 14 and the edge of the current collector 1 can be more than or equal to 1mm, so that the integrity of the welding area 14 can be ensured, the tab piece 3 can be conveniently welded on the current collector 1, and a welding seam with enough width can be ensured to be formed between the tab piece 3 and the current collector 1.

In practical use, burrs or spikes may be generated at the welded portions of the tab pieces 3, and the burrs or spikes may penetrate through the separator in the battery to cause an internal short circuit, which may seriously cause the burning or explosion of the battery. Therefore, as shown in fig. 5a and 5b, in the present embodiment, the tab piece 3 may further be covered with a protective layer 4, and the protective layer 4 covers at least a portion of the tab piece 3 located in the welding area 14, so as to protect the welding portion of the tab piece 3 through the protective layer 4. Through the covering effect of the protective layer 4, burrs or sharp burrs generated at the welding part of the pole lug piece 3 can be prevented from penetrating through the diaphragm, so that the safety performance of the battery is improved.

In order to facilitate the arrangement of the protection layer 4, the protection layer 4 may extend to the whole area where the covering electrode tab 3 is located along the length direction of the current collector 1, if the protection layer 4 covers the passage 13, the protection layer 4 located at the passage 13 may be disconnected, at this time, the shape and size of the through hole formed in the protection layer 4 may be consistent with the passage 13, or may be different from the passage 13, which is not limited in this embodiment.

For example, the protective layer 4 may be coated on only the tab sheet 3 located on one side surface of the current collector 1, for example, the protective layer 4 may be coated on only the tab sheet 3 located on the outer surface of the first conductive layer 1a, or the protective layer 4 may be coated on only the tab sheet 3 located on the outer surface of the second conductive layer 1 c. Alternatively, the protective layer 4 may be coated on both the tab pieces 3 provided on the outer surface of the first conductive layer 1a and the outer surface of the second conductive layer 1 c.

The protective layer 4 may be made of a conductive material or an insulating material, and the thickness of the protective layer 4 may be 5 to 50 μm, for example, the thickness of the protective layer 4 is 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, or 45 μm.

The pole piece 100 provided by this embodiment includes a current collector 1, the current collector 1 includes a first conductive layer 1a, a base layer 1b and a second conductive layer 1c, which are stacked in sequence, and the light base layer 1b is used to replace part of the conductive layers, so that the surface density of the current collector 1 is smaller, the weight of the battery is reduced, and the energy density of the battery is improved; meanwhile, when the battery is short-circuited due to mechanical abuse, the battery is heated to a certain temperature, the substrate layer 1b is easy to deform and shrink to damage the current collector 1 and cut off a current loop, so that the battery is not easy to burn or explode, and the safety performance of the battery can be improved. The electrode tab 3 is connected to the second region 12 of the current collector 1 not covered by the active material layer 2, and the electrode tab 3 passes through a passage 13 formed in the second region 12 of the current collector 1, and is partially attached to the surface of the first conductive layer 1a and partially attached to the surface of the second conductive layer 1c, so as to electrically connect the first conductive layer 1a and the second conductive layer 1c on both sides of the current collector 1.

Example two

Fig. 6 is a schematic flow chart of a manufacturing method of a pole piece according to a second embodiment of the present invention. As shown in fig. 6, this embodiment provides a method for manufacturing a pole piece 100, and the method is used to manufacture the pole piece 100 in the first embodiment.

Specifically, the preparation method of the pole piece 100 includes the following steps:

s100, a base layer 1b and a second conductive layer 1c are sequentially stacked on the first conductive layer 1a to form a current collector 1.

A current collector 1 having a trimmings structure is formed by sequentially laminating a base layer 1b and a second conductive layer 1c on the first conductive layer 1 a. Transition layers may be provided between the first conductive layer 1a and the base layer 1b and between the second conductive layer 1c and the base layer 1 b.

Illustratively, the first conductive layer 1a and the second conductive layer 1c may be metal layers or alloy layers, and the base layer 1b may be a polymer layer.

And S200, dividing the current collector 1 into a first area 11 and a second area 12 along the width direction of the current collector, and coating active material layers 2 on the surfaces of two sides of the current collector 1 in the first area 11.

By coating the active material layer 2 on both side surfaces of the current collector 1 in the first region 11, the current generated by the active material layer 2 is collected to the current collector 1.

S300, forming a via 13 in the second region 12 of the current collector 1, wherein the via 13 penetrates through the first conductive layer 1a, the base layer 1b, and the second conductive layer 1 c.

S400, after the tab piece 3 extends to the passage 13 along one side surface of the current collector 1, the tab piece 3 passes through the passage 13 and extends along the other side surface of the current collector 1, and the tab piece 3 is connected to the surface of the first conductive layer 1a and the surface of the second conductive layer 1 c.

The tab piece 3 is inserted through the through-passages 13 formed in the current collector 1 such that a partial section of the tab piece 3 is located on the outer surface of the first conductive layer 1a and a partial section of the tab piece 3 is located on the outer surface of the second conductive layer 1 c. In this way, the pole tab 3 is connected to the outer surface of the first conductive layer 1a and the outer surface of the second conductive layer 1c corresponding to the sections on the outer surface of the first conductive layer 1a and the outer surface of the second conductive layer 1c, respectively, so as to conduct the first conductive layer 1a and the second conductive layer 1c through the pole tab 3.

Wherein, the outer surface of the first conducting layer 1a and the outer surface of the second conducting layer 1c are both provided with welding areas 14, and after the tab pieces 3 are arranged, the tab pieces 3 are welded in the welding areas 14 of the outer surface of the first conducting layer 1a and the welding areas 14 of the outer surface of the second conducting layer 1 c.

After the tab pieces 3 are welded, the portions of the tab pieces 3 that extend beyond the width direction of the current collector 1 may be cut by a process such as laser cutting, and a plurality of tab branches 32 may be formed by cutting. In this way, the tab piece 3 is configured to connect a plurality of tab branches 32 to the tab body 31, the tab body 31 is connected to the current collector 1, and the tab branches 32 extend out of the current collector 1 in the width direction of the current collector 1.

Fig. 7 is a schematic structural diagram of a cell formed by winding a pole piece according to a second embodiment of the present invention. As shown in fig. 7, after the preparation of the electrode sheet 100 is completed, the positive electrode sheet and the negative electrode sheet may be wound together with the separator 200 to obtain a battery cell. And packaging the battery core by adopting an aluminum-plastic film, baking for 48h in a vacuum state to remove moisture, injecting electrolyte, and performing formation and sorting treatment to obtain the battery.

The performance parameters of the pole piece provided in this embodiment and the performance parameters of the pole piece serving as a reference are compared by a specific scheme below.

Example 1: as a specific implementation manner of this embodiment, the positive electrode current collector adopts a foil material with an Al-PET-Al structure, lithium cobaltate active slurry is coated on two side surfaces of the current collector to form an active material layer, an uncoated area is left on one side of the current collector along the width direction, a channel is opened in the uncoated area, and the shape of the channel is a rounded rectangle. And (3) enabling the tab pieces to penetrate through the passages and enabling the portions of the tab pieces, which are positioned on two sides of the current collector, to be respectively welded on the surfaces of the first conducting layer and the second conducting layer on the two sides. And then, cutting the part of the pole lug plate extending out of the width direction of the current collector into more than 1 pole lug branches with certain width and shape by a cutting process to obtain the positive pole piece with a plurality of pole lug branches.

The negative current collector adopts Cu foil as foil, graphite active material is coated on two side surfaces of the current collector to form active material layers, and similar to the positive pole piece, the electrode lug is welded in the uncoated area in the width direction of the current collector. And then, winding the positive pole piece, the negative pole piece and the diaphragm to obtain the winding core.

Comparative example 1: in one embodiment of the comparison, the positive electrode current collector uses an Al foil, lithium cobaltate active slurry is coated on both side surfaces of the current collector to serve as an active material layer, an uncoated region is left at least at one end of the current collector in the length direction, and a tab is welded in the uncoated region. The negative current collector adopts Cu foil as foil material, graphite active material is coated on the two side surfaces of the current collector to be used as active material layers, and a tab is welded in the uncoated area. And then, winding the positive pole piece, the negative pole piece and the diaphragm to obtain the winding core.

Comparative example 2: in another embodiment of the comparison, the positive electrode current collector adopts a foil material with an Al-PET-Al structure, lithium cobaltate active slurry is coated on the two side surfaces of the current collector to serve as an active material layer, at least one end of the current collector in the length direction is left with an uncoated area, and a tab is welded in the uncoated area. The negative current collector adopts Cu foil as foil, graphite active material is coated on the two side surfaces of the current collector to be used as active material layers, and a tab is welded in an uncoated area. And then, winding the positive pole piece, the negative pole piece and the diaphragm to obtain the winding core.

The winding cores obtained in the embodiment 1, the comparative example 1 and the comparative example 2 are subjected to packaging, liquid injection, formation, secondary packaging and capacity grading to obtain finished product battery cores. Then, testing internal resistance of each finished product battery cell through an internal resistance tester, and carrying out weight impact test under the conditions of: and (3) fully charging the finished battery cell, placing the battery cell on a plane, placing a steel column with the diameter of 15.8 +/-0.2 mm in the center of the battery cell, wherein the longitudinal axis of the steel column is parallel to the plane, and allowing a weight with the mass of 9.1 +/-0.1 kg to freely fall onto the steel column above the center of the battery from the height of 610 +/-25 mm.

The following test results were obtained:

item	Internal resistance of m omega	Energy density Wh/kg	Full electric weight impact (pass/test)
				Example 1	12.8	291.5	20/20
Comparative example 1	32	280	0/20
				Comparative example 2	50	295	20/20

It can be seen that the internal resistance of the finished cell of example 1 is much less than the internal resistance of the finished cells of comparative examples 1 and 2, and that the energy density of the finished cell of example 1 and the energy density of the finished cell of comparative example 2 are both higher, and the finished cell of example 1 can also pass the weight impact test.

EXAMPLE III

The present embodiment provides a battery, which includes the electrode plate of the first embodiment. The structure, function and working principle of the pole piece are described in detail in the first embodiment, and are not described herein again.

It is to be understood that the terms upper, lower, top, bottom, top end, bottom end, top end surface, bottom end surface, and the like referring to the present embodiment indicate the orientation based on the positional relationship of the installation and use state of the device or apparatus.

The embodiments or implementation modes in the present specification are described in a progressive manner, each embodiment is different from the other embodiments in point of description, and the same and similar parts among the embodiments can be referred to each other.

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; while the invention has been described in detail and with reference to the foregoing embodiments, it will 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; and such modifications and substitutions do not depart from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A pole piece is characterized by comprising a current collector, an active material layer and a pole lug, wherein the current collector comprises a first conducting layer, a base layer and a second conducting layer which are sequentially stacked;

the current collector is divided into a first area and a second area along the width direction of the current collector, and the active substance layer covers two side surfaces of the current collector in the first area; at least one passage is opened in the second region, the passage runs through the both sides surface of the thickness direction of mass flow body, utmost point ear piece passes the passage, and connects the surface of first conducting layer reaches the surface of second conducting layer.

2. The pole piece of claim 1, wherein the number of channels is one, the pole tab comprises a first section and a second section, the first section is attached to the first conductive layer, and the second section passes through the channels and is attached to the second conductive layer;

wherein, along the length direction of the current collector, the first section and the second section are located on two sides of the passage, or the first section and the second section are located on the same side of the passage.

3. The pole piece of claim 1, wherein the number of the passages is greater than or equal to two, each of the passages is arranged at intervals along the length direction of the current collector, and the pole lug sequentially penetrates through each of the passages.

4. The pole piece of any one of claims 1 to 3, wherein the passage is a conduction groove, and a notch of the conduction groove is positioned on the side surface of the current collector.

5. The pole piece as claimed in any one of claims 1 to 3, wherein the pole tab piece comprises a tab main body and a plurality of tab branches connected to the tab main body, and the plurality of tab branches are distributed at intervals along the length direction of the tab main body;

wherein, utmost point ear main part is connected on the surface of mass flow body, utmost point ear branch stretches out to outside the width direction of mass flow body.

6. The pole piece of claim 5, wherein a ratio of an extended length of the tab branch to a width of the tab body in a width direction of the current collector ranges from 0.5 to 5.

7. The pole piece of any one of claims 1 to 3, wherein a surface of the first conductive layer and a surface of the second conductive layer are each provided with a welding area, and the pole tab is welded to the first conductive layer and the second conductive layer in the welding area.

8. The pole piece of claim 7, further comprising a protective layer covering at least a portion of the pole tab within the weld region.

9. The pole piece of any one of claims 1 to 3, wherein the first and second conductive layers are metal layers and the base layer is a polymer layer.

10. A battery comprising a pole piece according to any one of claims 1 to 9.