CN217822875U

CN217822875U - Composite current collector, pole piece and battery cell

Info

Publication number: CN217822875U
Application number: CN202221409919.2U
Authority: CN
Inventors: 不公告发明人
Original assignee: Shanghai Jusheng Technology Co Ltd
Current assignee: Shanghai Jusheng Technology Co Ltd
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2022-11-15
Anticipated expiration: 2032-05-30

Abstract

The embodiment of the utility model discloses a composite current collector, pole piece and electric core, the composite current collector comprises a supporting layer, a first metal layer and a second metal layer, the supporting layer is provided with a first surface and a second surface which are opposite, the first metal layer is arranged on the first surface, the second metal layer is arranged on the second surface; the conductive carbon layer is arranged on at least one of the first metal layer and the second metal layer, so that the conductive performance of the surface layer of the composite current collector is improved, the internal resistance of the battery cell using the composite current collector is reduced, and the electrical performance and the safety performance of the battery cell are improved.

Description

Composite current collector, pole piece and battery cell

Technical Field

The utility model relates to a secondary battery technical field, concretely relates to compound mass flow body, pole piece and electric core.

Background

The current lithium ion battery mainly adopts metal foils (such as copper foil and aluminum foil) as current collectors, and the metal foils have high density, so that the improvement of the energy density of the battery is limited. In order to reduce the influence of copper foil or aluminum foil on the energy density of the battery, people prepare a composite current collector by depositing metal on the surface of a high polymer material with lower density, so that the weight of the current collector is reduced, and the energy density of the battery is improved; however, the resistance of such a composite current collector is greater than that of a metal foil current collector, which is disadvantageous in reducing the internal resistance of the battery.

SUMMERY OF THE UTILITY MODEL

An object of the embodiment of the utility model is to provide a compound mass flow body, pole piece and electric core can solve the above-mentioned at least partial defect that exists among the prior art.

In a first aspect, an embodiment of the present invention provides a composite current collector, including a support layer, a first metal layer, a second metal layer, and at least one conductive carbon layer; the support layer has opposing first and second surfaces; the first metal layer is disposed on the first surface; the second metal layer is arranged on the second surface; the conductive carbon layer is disposed on at least one of the first metal layer and the second metal layer. The conductive carbon layer has good conductive capability, so that the conductive performance of the surface layer of the composite current collector is improved, the internal resistance of a battery cell using the composite current collector is reduced, and the electrical performance of the battery cell is improved.

In some embodiments, the thickness of the first metal layer is 3-8 μm; and/or the thickness of the second metal layer is 3-8 μm. Through this kind of setting, be favorable to reducing the resistance of compound mass flow body, be favorable to guaranteeing to use the energy density of the electric core of compound mass flow body simultaneously, when the short circuit of emergence point.

In some embodiments, the support layer has a thickness of 5-12 μm. Through the arrangement, the mechanical strength of the composite current collector is favorably ensured, and the energy density and the safety performance of the battery cell using the composite current collector are favorably ensured.

In some embodiments, the conductive carbon layer has a thickness of 0.5-2.0 μm. Through the arrangement, the resistance of the composite current collector is further reduced, so that the internal resistance of the battery cell using the composite current collector is reduced, and the electrical performance of the battery cell is improved.

In some embodiments, the ratio of the sum of the thicknesses of the first metal layer and the second metal layer to the thickness of the support layer is (0.5-3.2): 1. through the arrangement, the resistance of the composite current collector is further reduced, and the electrical property of the battery cell is improved.

In some embodiments, the number of the conductive carbon layers is two, and the two conductive carbon layers are a first conductive carbon layer and a second conductive carbon layer respectively, the first conductive carbon layer is disposed on the first metal layer, and the second conductive carbon layer is disposed on the second metal layer; the thickness of the first conductive carbon layer is the same as or different from the thickness of the second conductive carbon layer. Through the arrangement, the resistance of the composite current collector is further reduced, and the electrical property of the battery cell is improved.

In a second aspect, an embodiment of the present invention further provides a pole piece, where the pole piece includes the composite current collector as described in the first aspect, and an active material layer; the active material layer is disposed on at least one side surface of the composite current collector. By adopting the composite current collector in the first aspect, the resistance of the pole piece is reduced, and the electrical performance of the battery cell using the pole piece is improved.

In some embodiments, the active material layer covers part of the surface of the composite current collector, the exposed part of the composite current collector not covered by the active material layer forms a tab, and the pole piece has at least two tabs. Because at least two tabs are arranged, the total area of the tabs of the pole piece is larger, the conductive performance of the pole piece is further enhanced, the internal resistance of the pole piece is reduced, and the heat dissipation performance of the pole piece is improved.

In a third aspect, an embodiment of the present invention further provides an electrical core, where the electrical core includes at least one pole piece as described in the second aspect. By adopting the pole piece of the second aspect, the internal resistance of the battery cell is favorably reduced, the discharge performance of the battery cell is favorably improved, and the energy density and the safety performance of the battery cell are ensured.

In a fourth aspect, an embodiment of the present invention further provides an electrical core, the electrical core includes a positive plate and a negative plate, the positive plate is a pole piece as in the second aspect, and a current collector of the negative plate is a copper foil. The pole piece of the second aspect is particularly applied to a positive pole piece of a battery cell, so that the weight of the positive pole piece is favorably reduced, and the electrical property of the positive pole piece is ensured; and meanwhile, the copper foil is used as a current collector of the negative plate, so that the thickness of the negative plate is favorably reduced, and the overall energy density and the electrical property of the battery cell are favorably improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

fig. 1 is a schematic structural view of a composite current collector according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional view of a pole piece according to an embodiment of the present invention;

fig. 3 is a top view of a pole piece according to an embodiment of the present invention.

Detailed Description

The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in detail. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, flows, components and circuits have not been described in detail so as not to obscure the present invention.

Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Unless the context clearly requires otherwise, throughout this specification, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".

In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.

Fig. 1 is a schematic structural view of a composite current collector according to an embodiment of the present invention.

Referring to fig. 1, the composite current collector 100 according to an embodiment of the present invention includes a support layer 110, a first metal layer 120, and a second metal layer 130. The support layer 110 has opposite first and second surfaces, the first metal layer 120 being disposed on the first surface, and the second metal layer 130 being disposed on the second surface.

The first and

second metal layers

120 and 130 may be formed on the first and second surfaces of the support layer 110 by a sputtering method, a vacuum deposition method, an ion plating method, a laser pulse deposition method, or other methods, respectively.

The first metal layer 120 and the second metal layer 130 are respectively selected from at least one of Ni, ti, cu, ag, au, pt, fe, co, cr, W, mo, al, mg, K, na, ca, sr, ba, si, ge, sb, pb, in, or Zn. The materials of the first metal layer 120 and the second metal layer 130 may be the same or different. In one embodiment, the materials of the first metal layer 120 and the second metal layer 130 may be selected from aluminum, which is beneficial to reduce the weight and cost of the current collector; the composite current collector 100 using aluminum as the first and

second metal layers

120 and 130 may function as a positive electrode current collector. In another embodiment, the material of the first metal layer 120 and the second metal layer 130 may be copper.

In some embodiments, the thickness of the first metal layer 120 is not less than 3 μm and not more than 8 μm, and the thickness of the second metal layer 130 is not less than 3 μm and not more than 8 μm. The thickness of the first metal layer 120 may be the same as or different from that of the second metal layer 130. Therefore, compared with the first metal layer 120 or the second metal layer 130 with the thickness of less than 3 μm, the cross-sectional areas of the first metal layer 120 and the second metal layer 130 with the thickness of 3 to 8 μm are larger, which is beneficial to ensuring the electron conductivity of the first metal layer 120 and the second metal layer 130 and reducing the internal resistance of the composite current collector 100. Meanwhile, compared with the first metal layer 120 or the second metal layer 130 with the thickness of more than 8 μm, the first metal layer 120 and the second metal layer 130 with the thickness of 3-8 μm can reduce the use of metal materials and reduce the manufacturing cost; the overall thickness of the composite current collector 100 is reduced, and the overall energy density of the battery cell is ensured; in addition, when the cell is short-circuited, the first metal layer 120 and/or the second metal layer 130 may be melted to form an open circuit, so as to ensure the use safety of the cell.

The first metal layer 120 and the second metal layer 130 may have the same thickness or different thicknesses, as necessary. In this embodiment, the first metal layer 120 and the second metal layer 130 may have the same thickness, so that the performance of both sides of the composite current collector 100 has uniformity.

In some embodiments, the support layer 110 includes one or more polymer material layers, for example, an organic polymer material film may be used, so that the weight of the composite current collector 100 may be reduced, which is beneficial to increase the energy density of a battery cell, and at the same time, the battery cell using the composite current collector 100 has good safety when receiving an external force impact. For example, the polymer material layer may employ one or more of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, polyvinylidene fluoride-hexafluoropropylene, poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene oxide, polyester, or polysulfone and derivatives thereof.

In some embodiments, the thickness of the support layer 110 is not less than 5 μm and not greater than 8 μm. Not only can the support layer 110 have sufficient mechanical strength be ensured, but also the reduction of the energy density of the battery cell caused by the excessive increase of the thickness of the current collector due to the excessive thickness of the support layer 110 can be avoided.

In some embodiments, the ratio of the sum of the thicknesses of the first and

second metal layers

120 and 130 to the thickness of the support layer is (0.5-3.2): 1, for example, may be 0.5: 1. 1: 1. 2: 1. 3.2:1 or other ratio. Therefore, the thickness ratio of the metal layer in the composite current collector 100 is in a higher range, which is beneficial to reducing the resistance of the composite current collector 100. The composite current collector 100 may have a resistance close to that of an all-metal current collector while reducing thickness and weight, as compared to an all-metal current collector of the same thickness.

In one embodiment, as shown in fig. 1, the composite current collector 100 includes two conductive carbon layers 140, 150, the two conductive carbon layers 140, 150 being a first conductive carbon layer 140 and a second conductive carbon layer 150, respectively, the first conductive carbon layer 140 being disposed on the first metal layer 120, the second conductive carbon layer 150 being disposed on the second metal layer 130. Thereby, the conductive capability of the composite current collector 100 can be enhanced, and the resistance can be reduced. The first and second conductive carbon layers 140 and 150 may be the same or different in composition. By adding the conductive carbon layers 140 and 150, the conductive capability of the composite current collector 100 can be effectively improved, which is beneficial to reducing the internal resistance of a battery cell using the composite current collector 100.

The conductive carbon layers 140, 150 comprise carbon materials. In some embodiments, the carbon material comprises at least one of graphene, carbon nanotubes, carbon nanohorns, graphite, activated carbon, carbon fibers, carbon black, or mesocarbon microbeads.

In some embodiments, the conductive carbon layers 140, 150 further include a first binder and a first conductive agent. The conductive carbon layers 140 and 150 may be disposed on the surfaces of the first metal layer 120 and/or the second metal layer 130 by roll coating, spray coating, or the like. For example, the carbon material, the first binder and the first conductive agent may be added into a solvent and mixed uniformly to form a slurry, and then the slurry is sprayed on the surface of the first metal layer 120 and/or the second metal layer 130 and dried to form the conductive carbon layers 140 and 150 having a certain thickness. Wherein, the solvent can be pure water.

The first binder may be at least one selected from polyacrylic acid, styrene-butadiene rubber, sodium carboxymethylcellulose, polystyrene-acrylate, or polyacrylonitrile multipolymer.

The first conductive agent may include at least one of natural graphite, artificial graphite, carbon nanotubes, graphene, graphite alkyne, vapor grown carbon fiber, or other conductive agents. Specific examples of commercially available conductive agents may include acetylene black series products of Chevron Chemical Company (Chevron Chemical Company), danka black of Danka Singapore Private Company Limited (Denka Singapore Private Limited), products of Gulf Oil Company (Gulf Oil Company), etc., ketjen black, EC series products of Emmet Company (Armak Company), vulcan XC-72 of Cabot Company (Cabot Company), and Super-P of Timcal Company.

The thickness of the conductive carbon layers 140, 150 may be selected as desired. In some embodiments, the conductive carbon layers 140, 150 have a thickness of no less than 0.5 μm and no greater than 2.0 μm. When the thickness of the conductive carbon layers 140, 150 is too small, the conductive carbon layers 140, 150 may not function well to reduce the resistance of the composite current collector 100. When the thickness of the conductive carbon layers 140 and 150 is too large, it is not favorable to ensure the energy density of the cell. The thickness of the first conductive carbon layer 140 and the second conductive carbon layer 150 may be the same or different. The thickness of the conductive carbon layers 140 and 150 accounts for a smaller percentage of the total thickness of the composite current collector 100, which not only can effectively reduce the resistance of the composite current collector 100, but also can ensure that the composite current collector 100 has smaller thickness and weight, and is beneficial to improving the energy density of a battery cell using the composite current collector 100.

The embodiment of the utility model provides a still relate to a pole piece, this pole piece includes the utility model discloses at least some compound mass flow body 100 in the above-mentioned embodiment.

Fig. 2 is a schematic cross-sectional view of a pole piece according to an embodiment of the present invention; fig. 3 is a top view of a pole piece according to an embodiment of the present invention. Referring to fig. 2 and 3, the pole piece further includes an active material layer 200, the active material layer 200 being disposed on at least one side surface of the composite current collector 100. In some embodiments, as shown in fig. 2, the active material layer 200 is disposed on both side surfaces of the composite current collector 100. When the first conductive carbon layer 140 is disposed on the first metal layer 120 and the second conductive carbon layer 150 is disposed on the second metal layer 130, an active material layer is disposed on the surfaces of the first conductive carbon layer 140 and the second conductive carbon layer 150. Through adopting the utility model discloses compound mass flow body 100 in at least some embodiments, the pole piece has higher energy density and internal resistance.

The active material layer 200 covers a part of the surface of the composite current collector 100, and the exposed part of the composite current collector 100 (i.e., the part of the composite current collector 100 not covered by the active material layer) forms a tab a, which is used as a structure for current extraction or introduction. Preferably, the pole piece is provided with at least two pole lugs A, so that the total area of the pole lugs A on the pole piece is increased, the internal resistance of the pole lugs A can be reduced, and meanwhile, the heat dissipation performance of the pole piece can be improved. In one embodiment, the pole piece has two tabs a, and the two tabs a are respectively disposed at two ends of the pole piece, which are disposed on the back side.

The pole piece can be a positive pole piece or a negative pole piece. In some embodiments, the pole piece is a positive pole piece, and the active material layer 200 includes a positive active material, a positive conductive agent, and a positive binder. The positive active material may include at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, or lithium nickel cobalt aluminate. The positive electrode conductive agent may include at least one of Super-P, acetylene black, ketjen black, carbon nanotubes, graphene, grapyne, or vapor grown carbon fiber. The positive electrode binder includes at least one of polyvinylidene fluoride, acrylate or styrene butadiene rubber. Will the utility model discloses in the positive plate is applied to the pole piece, be favorable to reducing the weight of positive plate, reducing the internal resistance of positive plate, and then make the internal resistance of the electric core that uses this positive plate reduce and energy density improves. Of course, the tab may be a negative tab, and the active material layer 200 of the negative tab may include a negative active material, a negative conductive agent, and a negative binder, respectively.

The embodiment of the utility model provides a still relate to an electricity core, this electricity core has used the utility model discloses pole piece in at least partial above-mentioned embodiment. The battery cell comprises a positive plate, a negative plate, a diaphragm and electrolyte. The positive plate, the negative plate and the diaphragm are stacked to form an electrode assembly, the diaphragm is arranged between the adjacent positive plate and the negative plate, and the electrode assembly can adopt a winding type structure or a lamination type structure. And (3) putting the electrode assembly into a packaging structure (such as a packaging bag), injecting electrolyte, and then carrying out processes such as packaging, formation and the like to obtain the battery core. Through adopting the utility model discloses pole piece in at least some above-mentioned embodiments for the internal resistance of electric core obtains reducing, and electric core has higher energy density simultaneously, and can have better security performance.

The positive plate and the negative pole piece of electricity core can all adopt the embodiment of the utility model provides an in the pole piece, also can only wherein some pole pieces adopt the embodiment of the utility model provides an in the pole piece. In an embodiment, the positive plate of the electric core adopts the pole piece in at least some of the above embodiments of the present invention, and the current collector of the negative plate adopts a metal current collector, for example, a copper foil can be adopted as the current collector of the negative plate. The copper foil can be prepared to be thinner, so that the copper foil is adopted as the current collector of the negative plate, which is beneficial to ensuring the energy density of the battery cell.

Preferably, the cell designs the surface current of the pole piece according to the fusing conditions of the first metal layer 120 and the second metal layer 130, so as to ensure that the first metal layer 120 and the second metal layer 130 can be fused by the current during the internal short circuit.

In order to make the present invention better understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to the specific embodiments.

Example 1

In this example, a cell was prepared. Wherein, the positive plate in this electricity core adopts the embodiment of the utility model provides an in the compound mass flow body 100. The preparation process comprises the following steps:

(1) And (4) preparing the positive plate. The positive electrode sheet includes a composite current collector 100 and an active material layer. As shown in fig. 1, the composite current collector 100 includes a support layer 110, a first metal layer 120, a second metal layer 130, a first conductive carbon layer 140, and a second conductive carbon layer 150. A first metal layer 120 is disposed on a first surface of the support layer 110, a second metal layer 130 is disposed on a second surface of the support layer 110, a first conductive carbon layer 140 is disposed on the first metal layer 120, and a second conductive carbon layer 150 is disposed on the second metal layer 130. As shown in fig. 2, there are two active material layers 200, and the two active material layers 200 are disposed on the first conductive carbon layer 140 and the second conductive carbon layer 150, respectively. As shown in table 1 below, the thickness of the support layer was 5 μm, the thickness of the first metal layer 120 was 3 μm, the thickness of the second metal layer 130 was 3 μm, the thickness of the first conductive carbon layer 140 was 0.5 μm, and the thickness of the second conductive carbon layer 150 was 0.5 μm.

The preparation process of the positive plate comprises the following steps: taking a PE film with the thickness of 5 mu m as a supporting layer, and respectively preparing Al coatings on two sides of the PE film by a vacuum deposition method to be used as a first metal layer and a second metal layer, wherein the thicknesses of the first metal layer and the second metal layer are both 3 mu m. Then, the carbon material, PAA, CMC and Super-P are mixed according to the mass ratio of 94.3%:1.5%:1.2%: mixing the components in a proportion of 3 percent, adding the mixture into pure water, and preparing conductive carbon layer slurry. And coating the conductive carbon layer slurry on the surfaces of the first metal layer and the second metal layer, and drying to form a first conductive carbon layer and a second conductive carbon layer to obtain a composite current collector. The first conductive carbon layer and the second conductive carbon layer each have a thickness of 0.5 μm. And uniformly coating the slurry containing the nickel cobalt lithium manganate serving as the positive electrode active material on the surfaces of the first conductive carbon layer and the second conductive carbon layer, and reserving two lug positions at two ends of the composite current collector for not coating so as to facilitate welding. And cutting the electrode lugs after drying, and dividing and cutting to obtain the positive plate.

(2) Preparing a negative plate: and (2) using a copper foil as a negative current collector, uniformly coating slurry containing a negative active material graphite on the negative current collector, drying, cold pressing, cutting a tab, slitting and cutting to obtain a pole piece.

(3) Preparing an electric core: and assembling the positive plate, the negative plate and the diaphragm by adopting a lamination process, injecting lithium ion electrolyte, packaging and forming to obtain the battery cell. The sheet surface current of the obtained cell was 3A.

Example 2

In this embodiment, a battery cell is prepared, and a preparation process is as follows:

(1) The structure and the preparation method of the positive electrode sheet were substantially the same as in example 1, as shown in table 1, except that: the first metal layer and the second metal layer of example 2 each had a thickness of 8 μm.

(2) Preparing a negative plate: same as in example 1.

(3) Preparing an electric core: the preparation method is the same as in example 1. The sheet surface current of the obtained cell was 4.8A.

Example 3

(1) The structure and the preparation method of the positive electrode sheet were substantially the same as in example 1, as shown in table 1, except that: the first metal layer and the second metal layer of example 3 each had a thickness of 5 μm.

(2) Preparing a negative plate: same as in example 1.

(3) Preparing an electric core: the preparation was carried out in the same manner as in example 1. The sheet surface current of the obtained cell was 4.0A.

Example 4

(1) The structure and the preparation method of the positive electrode sheet were substantially the same as in example 1, as shown in table 1, except that: the supporting layer of example 4 had a thickness of 12 μm, and the first and second conductive carbon layers each had a thickness of 2 μm.

(2) Preparing a negative plate: same as in example 1.

(3) Preparing an electric core: the preparation was carried out in the same manner as in example 1.

Example 5

(1) The structure and the preparation method of the positive electrode sheet were substantially the same as in example 1, as shown in table 1, except that: example 5 the supporting layer had a thickness of 8 μm and the first and second conductive carbon layers had a thickness of 1 μm each.

(2) Preparing a negative plate: same as in example 1.

Comparative example 1

The comparative example prepared an electrical core, the preparation process was as follows:

(1) Preparing a positive plate: coating slurry containing a positive active material nickel cobalt lithium manganate on the surfaces of two sides of an aluminum foil with the thickness of 12 mu m, drying, and then cutting tabs, strips and pieces to obtain a positive plate.

(2) Preparing a negative plate: same as in example 1.

Comparative example 2

The comparative example prepares a cell, and the preparation process is as follows:

(1) Preparing a positive plate: as shown in table 1, the positive electrode sheet in comparative example 2 includes a support layer, a first metal layer, and a second metal layer, but does not have the first and second conductive carbon layers of the positive electrode sheet of example 1, as compared to example 1.

(2) Preparing a negative plate: same as in example 1.

TABLE 1

The cells of examples 1 to 5 and comparative examples 1 and 2 were subjected to a film resistance test, a cell internal resistance test and a needle punching test, and the test results are shown in table 2 below.

TABLE 2

	Diaphragm resistance/mohm	Cell internal resistance/mohm	Needle prick test
				Example 1	320	2.1	Through, without fire and explosion
Example 2	320	2.2	Through, without fire and explosion
				Example 3	310	2.0	Through, without fire and explosion
Example 4	325	2.0	Through, without fire and explosion
				Example 5	340	2.0	Through, without fire and explosion
Comparative example 1	340	2.2	Fire without passing through
				Comparative example 2	970	4.8	Fire without passing through

Referring to table 2, the cell of comparative example 1 had a diaphragm resistance of 340mohm; the film resistances of the cells of examples 1-5 were 320mohm, 310mohm, 325mohm, and 340mohm, respectively, which were lower than or equal to the film resistance of the cell of comparative example 1; the diaphragm resistance of the comparative example 2 cell was 970mohm. Therefore, after the first conductive carbon layer and the second conductive carbon layer are respectively arranged on the first metal layer and the second metal layer, the diaphragm resistance of the composite current collector can be obviously reduced, and the diaphragm resistance of the composite current collector is equal to or even lower than that of the metal current collector.

In the cell internal resistance test, the cell internal resistance of comparative example 1 was 2.2mohm; the cell internal resistances of the embodiments 1 to 5 are respectively 2.1mohm, 2.2mohm, 2.0mohm and 2.0mohm, which are lower than or equal to the cell internal resistance of the comparative example 1; the internal cell resistance of comparative example 2 was 4.8mohm. Therefore, the utility model discloses after the composite current collector sets up first conductive carbon layer and second conductive carbon layer respectively on first metal level and second metal level, can obviously reduce the internal resistance of the electric core of using composite current collector, the internal resistance that makes the electric core that adopts composite current collector equal to or is less than the internal resistance of the electric core that adopts the metal current collector.

In the needling test, the electric cores of the embodiments 1 to 5 do not generate the phenomena of fire or explosion, and pass the needling test; the cells of comparative examples 1 and 2, on the other hand, produced a fire in the needle test and failed the needle test. Therefore, the utility model discloses the composite current collector of embodiment has better security performance, has higher thermal stability when the inside short circuit of electric core.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite current collector, comprising:

a support layer having opposing first and second surfaces;

a first metal layer disposed on the first surface;

a second metal layer disposed on the second surface; and

at least one conductive carbon layer disposed on at least one of the first metal layer and the second metal layer.

2. The composite collector of claim 1 wherein the thickness of the first metal layer is 3-8 μ ι η; and/or

The thickness of the second metal layer is 3-8 μm.

3. The composite current collector of claim 1 or 2, wherein the thickness of the support layer is 5-12 μ ι η.

4. The composite current collector of claim 1 or 2, wherein the conductive carbon layer has a thickness of 0.5-2.0 μ ι η.

5. The composite current collector of claim 1 or 2, wherein the ratio of the sum of the thicknesses of the first and second metal layers to the thickness of the support layer is (0.5-3.2): 1.

6. the composite current collector of claim 1, wherein the number of conductive carbon layers is two, and the two conductive carbon layers are a first conductive carbon layer and a second conductive carbon layer, respectively, the first conductive carbon layer being disposed on the first metal layer and the second conductive carbon layer being disposed on the second metal layer;

the thickness of the first conductive carbon layer is the same as or different from the thickness of the second conductive carbon layer.

7. A pole piece, comprising:

the composite current collector of any one of claims 1-6; and

an active material layer disposed on at least one side surface of the composite current collector.

8. The pole piece of claim 7, wherein the active material layer covers a portion of the surface of the composite current collector, the exposed portion of the composite current collector not covered by the active material layer forms a tab, and the pole piece has at least two tabs.

9. A cell comprising at least one pole piece according to any one of claims 7 to 8.

10. An electric core, characterized by comprising a positive plate and a negative plate, wherein the positive plate is the plate of any one of claims 7 to 8, and the current collector of the negative plate is copper foil.