CN115810759A

CN115810759A - Flexible composite current collector, preparation method thereof, pole piece and battery

Info

Publication number: CN115810759A
Application number: CN202211266154.6A
Authority: CN
Inventors: 缪伟振; 路惠舒; 宋书涛; 张小细
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2022-10-17
Filing date: 2022-10-17
Publication date: 2023-03-17

Abstract

The invention relates to the technical field of batteries, in particular to a flexible composite current collector, a preparation method thereof, a pole piece and a battery. The flexible composite current collector comprises a metal grid substrate and a composite material coated on two surfaces of the metal grid substrate and filling grid holes, wherein the composite material comprises a high molecular polymer and a conductive agent, on one hand, the metal grid substrate has the characteristic of light weight, on the other hand, the metal grid substrate has better flexibility, the composite material is coated on two surfaces of the metal grid substrate and fills the grid holes, so that when the flexible composite current collector is applied to a battery, slurry is prevented from leaking out of the grid holes, in addition, the composite material comprises the high molecular polymer and the conductive agent, the conductive agent is bonded to the metal grid substrate through the high molecular polymer, and the conductive agents are connected with each other and communicated with a metal structure, so that an excellent conductive network is formed in the flexible composite current collector.

Description

Flexible composite current collector, preparation method thereof, pole piece and battery

Technical Field

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

Background

The lithium ion battery is the most widely used battery technology at present, and has the characteristics of high capacity, long cycle life and the like. With the development and popularization of intelligent wearable electronic equipment, especially the emergence of flexible electronic devices, people also correspondingly put forward requirements on light, thin, flexible and the like for lithium ion battery requirements.

The lithium ion battery mainly comprises components of a positive electrode, a negative electrode, electrolyte, a diaphragm and a shell, wherein the preparation and development of the flexible electrode are the key points of the whole flexible battery. At present, in the traditional electrode preparation process, a positive electrode (negative electrode) material, a conductive agent, a binder and the like are mixed and stirred to form slurry, and the slurry is coated on a metal current collector to prepare an electrode plate, but the metal current collector is easy to generate fatigue in the long-term bending process, so that the electrode is broken, and the use of a battery is influenced.

Disclosure of Invention

The invention mainly aims to provide a flexible composite current collector, aiming at improving the flexibility of the current collector, improving the service performance of the current collector and prolonging the service life of the current collector.

In order to achieve the above object, the present invention provides a flexible composite current collector, which includes:

a metal grid substrate; and

the composite material is coated on two surfaces of the metal grid base material and is filled in grid holes, and the composite material comprises a high molecular polymer and a conductive agent.

Optionally, the opposite ends of the metal grid substrate are provided with tabs.

The electrode lugs are arranged at the two opposite ends of the metal grid substrate, so that the flexible composite current collector is conveniently applied to the battery, and the electric conduction of the battery core and the external circuit structure is realized.

Optionally, the metal grid substrate is defined to have a length direction and a width direction, the tabs are disposed at two ends of the width direction, and the tabs are metal sheets.

Considering that the flexible composite current collector is generally rolled along the length direction in the rolling process, the tabs are arranged at two ends in the width direction at the moment, and after the flexible composite current collector is rolled along the length direction, the tabs protrude out of two ends of the rolled flexible composite current collector. Compared with the lug with the net structure, the lug with the metal sheet is better in overcurrent capacity of current due to the fact that the lug with the metal sheet has a larger surface area, and the lug is the metal sheet in order to improve the overcurrent capacity of the current.

Optionally, the metal sheet is formed with the grid holes;

and/or the width of the tab is 5mm-50mm;

and/or the metal grid substrate and the pole lug are of an integrally formed structure.

Because the weight energy density of the metal sheet with the net-shaped structure is higher, under some scenes, grid holes can be formed in the metal sheet, so that the lug is the metal sheet with the net-shaped structure, and the weight energy density of the battery is improved. The width of utmost point ear can influence overcurrent capacity and weight energy density, and the width of utmost point ear in this application is 5mm-50mm, can set up the width of utmost point ear as required and be 5mm, 10mm, 20mm, 30mm, 40mm, 50mm. For example, a larger width of the tab region (30 mm-50 mm) results in a higher tab height, lower gravimetric energy density and better current capacity, whereas a smaller width of the tab region (5 mm-30 mm) results in a lower tab height, higher gravimetric energy density and poorer current capacity. In order to improve the overall performance of the flexible composite current collector and avoid the tab from breaking and falling off from the metal grid substrate, the metal grid substrate and the tab are of an integrally formed structure, namely, the tab is formed by extending from the end part of the metal grid substrate, and the tab and the metal grid substrate are of an integral structure.

Optionally, the metal grid substrate comprises a plurality of metal wires, and the plurality of metal wires are arranged in a cross manner.

In order to form the metal grid substrate of the mesh structure, it may be formed by a wire weaving method.

Optionally, the metal grid substrate is an integrally formed structure;

and/or the shape of the grating holes comprises rhombic holes, square holes, rectangular holes or wavy holes;

and/or defining the area of the metal grid base material as S1, and defining the sum of the areas of the grid holes on the metal grid base material as S2, wherein S2: the range of S1 is 40-70%.

In order to improve the overall performance of the metal grid base material, the metal grid base material is of an integrally formed structure. In order to further improve the ductility of the metal grid base material with a net structure and change the shape of the grid holes, flexible metal grid base materials with different ductility characteristics can be obtained, for example, the grid holes can be rhombic holes, square holes, rectangular holes or wavy holes, wherein the rhombic holes are preferred, and the ductility is better.

In order to represent the amount of the composite material loaded on the reticular metal grid base material, the area of the metal grid base material is defined as S1, the sum of the areas of grid holes on the metal grid base material is S2, S2: the larger the value of S1 is, the larger the area occupied by the grid holes is, the more the composite material is loaded, and in consideration of the flexibility and the conductivity of the flexible composite current collector, S2: s1 ranges from 40% to 70%, for example, 40%, 50%, 60%, 70%. Under certain conditions, S2: the value of S1 may be a measure of the density of the wire, for example, in the case of a uniform distribution of grid holes, S2: the larger the value of S1, indicating more open pores, the more open wires, and conversely, S2: the smaller the value of S1, the fewer the grid holes, the denser the wires.

Optionally, if the maximum width of the grid holes is defined as D, then: d is more than 0mm and less than or equal to 5mm;

and/or, the thickness of the metal grid substrate is defined as H1, and the following conditions are satisfied: h1 is more than or equal to 5 mu m and less than or equal to 100 mu m;

and/or, defining the thickness of the flexible composite current collector as H2, and satisfying the following conditions: h2 is more than or equal to 10 mu m and less than or equal to 300 mu m.

Considering that the larger the grid hole is, the polymer is difficult to spread and coat at the grid hole, easily leads to leaking the material, therefore, the maximum width of defining the grid hole is D, then satisfies: d is more than 0mm and less than or equal to 5mm, namely, the maximum width D of the grating holes can be 1mm, 2mm, 3mm, 4mm and 5mm, and is specifically set according to requirements.

In order to obtain a reticular thin metal grid substrate with uniform thickness, the thickness of the metal grid substrate is defined as H1, the thickness of the metal grid substrate is selected to be within the range of 5 mu m and H1 and 100 mu m so as to facilitate the subsequent coating of the composite material on the metal grid substrate, and the thickness of the metal grid substrate is H1 which can be 5 mu m, 10 mu m, 20 mu m, 30 mu m, 40 mu m, 50 mu m, 60 mu m, 70 mu m, 80 mu m, 90 mu m and 100 mu m.

In order to make the cladding of combined material well on the metal grid substrate, and realize the fine pliability and the performance of flexible composite current collector, the thickness of defining flexible composite current collector is H2, then satisfies: h2 is 10 μm or less and 300 μm or less, and H2 may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 150, 200 μm, 250 μm, or 300 μm.

Optionally, the ratio of the high molecular polymer to the conductive agent is (100;

and/or the high molecular polymer comprises a water-insoluble high molecular polymer or an oil-insoluble high molecular polymer;

and/or the conductive agent comprises at least one of carbon nano tube, graphene, graphite, carbon fiber, carbon black and metal powder;

and/or the shape of the conductive agent is one or more of granular shape, linear shape and sheet shape.

Effect of the polymer in the composite substrate: firstly, connecting a metal grid substrate and a conductive agent to form a conductive network; and secondly, the metal grid holes are filled, so that slurry is prevented from leaking out of the grid holes during coating. The conductive agent is uniformly distributed in the high molecular polymer, and the conductive agents are connected with each other and communicated with the metal mesh structure at a proper ratio to form a good conductive network in the whole flexible composite current collector, wherein the weight ratio of the high molecular polymer to the conductive agent is (100. 1:100.

In order to avoid the phenomenon that some substances possibly exist in the cathode material, the anode material and the electrolyte can dissolve the high-molecular polymer to cause material leakage, for the aqueous cathode and anode slurry, the high-molecular polymer adopts a non-water-soluble high-molecular polymer, namely, the high-molecular polymer is not soluble in the aqueous substance to avoid the high-molecular polymer from being dissolved after contacting the aqueous material; for oily cathode and anode slurry, the high molecular polymer is non-oil-soluble, i.e. the high molecular polymer is insoluble in oily substances, so that the high molecular polymer is prevented from being dissolved after contacting oily materials.

The conductive agent is mainly used for conducting electricity, and the material with the conductive function can be selected according to needs, for example, at least one of carbon nanotubes, graphene, graphite, carbon fibers, carbon black and metal powder can be selected, that is, one of the conductive agents can be selected, or a mixture of two or more of the conductive agents can be selected, and the conductive agent is specifically selected according to needs. The shape of the conductive agent is not limited, and may be the shape of the conductive agent itself, or a specific shape after processing, and specifically is not limited, and may be one or more of granular shape, linear shape, and sheet shape, that is, one of the shapes, or a mixture of a plurality of shapes, which are specifically selected as needed.

Optionally, the water-insoluble high molecular polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, a polyacrylate binder, styrene butadiene rubber, aramid, polyacrylonitrile, polyacrylic acid and polymethyl methacrylate;

and/or the non-oil-soluble high molecular polymer comprises one or more of styrene-butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, nitrile rubber and hydrogenated nitrile rubber.

The present application still provides a pole piece, the pole piece includes the mass flow body and sets up active material on the mass flow body, wherein, the mass flow body does flexible composite current collector. The flexible composite current collector is applied to the pole piece, so that the bending performance of the pole piece is improved.

The present application further provides a battery, the battery comprising: the cathode electrode plate, the anode electrode plate, the isolating membrane and the electrolyte, wherein the cathode electrode plate and/or the anode electrode plate are the electrode plates. The flexible composite current collector is applied to the pole piece, so that the bending performance of the pole piece is improved, and the use safety of the battery is improved.

The application also provides a preparation method of the flexible composite current collector, which comprises the following steps:

providing a metal grid substrate;

coating composite materials on two surfaces of the metal grid base material, and filling grid holes in the metal grid base material to obtain the coated metal base material;

and drying the metal base material to obtain the flexible composite current collector.

The flexible composite current collector has the advantages of relatively low substrate cost and simple process, and can be widely applied to industrial production.

Optionally, before the step of coating the composite material on the two surfaces of the metal grid substrate, the method further comprises the following steps:

and rolling the metal grid base material to obtain the rolled metal grid base material.

Considering that the provided metal grid base material may have the phenomena of uneven thickness, burrs and the like, the metal grid base material is rolled before the step of coating the composite material on the two surfaces of the metal grid base material, and the rolled metal grid base material is obtained.

Optionally, in the step of drying the metal substrate to obtain the flexible composite current collector, the method includes the following steps:

and drying the metal base material, and rolling the dried metal base material to obtain the flexible composite current collector.

In the process of coating the composite material, the composite material has the problem of uneven coating, and in order to obtain the flexible composite current collector which is thin in thickness, flat in surface, free of slurry leakage, good in conductivity and light in weight, after the step of drying the metal base material, rolling is carried out, so that the rolled flexible composite current collector is obtained.

and reserving preset widths at two opposite ends of the metal grid substrate to form the tabs.

In order to conveniently prepare the lug, the preset width is reserved at the two opposite ends of the metal grid substrate directly to form the lug, so that the situation that the lug needs to be further arranged on the metal grid substrate subsequently is avoided, and the lug is one part of the metal grid substrate, so that the connection of the lug on the metal grid substrate is firmer.

Optionally, in the step of providing a metal grid substrate, comprising:

forming holes on a metal sheet to obtain the metal grid substrate;

or reserving preset widths at two opposite end parts of the metal sheet to form tabs, and forming holes in the middle of the metal sheet to obtain the metal grid substrate.

The metal grid substrate is obtained by forming holes on the metal sheet, so that the overall performance of the metal grid substrate can be improved.

Because the structure of the tab can influence the performance of the tab, the tab with the metal net structure has higher weight energy density and poorer overcurrent capacity compared with the tab with the metal sheet structure under the condition of the same area, and therefore, the tab with the metal net structure or the tab with the metal sheet structure can be selected according to actual needs. For example, in the process of preparing the metal grid substrate, according to requirements, the opposite two ends of the metal sheet are reserved with preset widths to form the tabs, and holes are formed in the middle of the metal sheet to obtain the metal grid substrate with holes, so that the tabs with the metal sheet-shaped structures are obtained. In order to obtain the tab with a metal net structure, holes can be formed in the whole metal sheet so that the part for forming the tab is also in the net structure

Optionally, in the step of providing a metal grid substrate, comprising:

providing a plurality of metal wires, and arranging the metal wires in a mutually crossed manner to form the metal grid base material.

The method of providing a metal grid substrate further includes forming the metal grid substrate by weaving a plurality of metal wires in an interdigitated arrangement.

The application discloses flexible compound mass flow body for improve the flexibility of mass flow body, improve the performance of mass flow body, prolong the life of mass flow body. The flexible composite current collector comprises a metal grid substrate and a composite material coated on two surfaces of the metal grid substrate and filling grid holes, wherein the composite material comprises a high molecular polymer and a conductive agent, on one hand, the metal grid substrate has the characteristic of light weight, on the other hand, the metal grid substrate has better flexibility, the composite material is coated on two surfaces of the metal grid substrate and fills the grid holes, so that when the flexible composite current collector is applied to a battery, slurry is prevented from leaking out of the grid holes, in addition, the composite material comprises the high molecular polymer and the conductive agent, the conductive agent is bonded to the metal grid substrate through the high molecular polymer, and the conductive agents are connected with each other and communicated with a metal structure, so that an excellent conductive network is formed in the flexible composite current collector. Based on the characteristics of excellent flexibility, conductivity, light weight and the like of the flexible composite current collector, the service performance of the flexible composite current collector can be effectively improved.

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 described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

Fig. 1 is a method of making a flexible composite current collector of the present invention;

FIG. 2 is a schematic top view of a rolled metal grid substrate according to a previous embodiment of the present invention;

FIG. 3 is a schematic top view of the rolled metal grid substrate of FIG. 2;

FIG. 4 is a schematic top view of the metal grid substrate of FIG. 3 after being coated with a composite material;

FIG. 5 is a schematic top view of another embodiment of the metal grid substrate of the present invention before rolling;

FIG. 6 is a schematic top view of the rolled metal grid substrate of FIG. 5;

FIG. 7 is a schematic top view of the metal grid substrate of FIG. 6 after being coated with a composite material;

fig. 8 is a schematic sectional structure view of the wire of the present invention before and after rolling.

The reference numbers illustrate:

reference numerals	Name(s)	Reference numerals	Name (R)
				100	Metal grid substrate	30	Pole ear
10	Grid hole	40	Composite material
				20	Metal wire

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all directional indicators (such as up, down, left, right, front, back \8230;) in the embodiments of the present invention are only used to explain the relative positional relationship between the components, the motion situation, etc. in a specific posture (as shown in the attached drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the expression "and/or" as used throughout is meant to encompass three juxtaposed aspects, exemplified by "A and/or B", including either the A aspect, or the B aspect, or aspects in which both A and B are satisfied. In addition, technical solutions between the embodiments may be combined with each other, but must be based on the realization of the technical solutions by a person skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The current collector refers to a structure or a part for collecting current, and in the lithium ion battery, mainly refers to metal foils, such as copper foil and aluminum foil. The current collector serves as a substrate for attaching a positive electrode active material or a negative electrode active material, and functions to collect current generated by the active material and output the current to the outside. Generally, aluminum foil is used as a positive current collector, and copper foil is used as a negative current collector.

In the traditional electrode preparation process, a positive electrode (negative electrode) material, a conductive agent, a binder and the like are mixed and stirred to form slurry, and the slurry is coated on a metal current collector to prepare an electrode plate, but the metal current collector is easy to generate fatigue in a long-term bending process, so that the electrode is broken, and the use of a battery is influenced.

In order to provide a flexible mass flow body to solve the long-term electrode fracture scheduling problem that buckles and lead to of mass flow body, this application provides a flexible composite mass flow body, and this flexible composite mass flow body improves the flexibility of mass flow body, makes the performance of mass flow body obtain promoting, prolongs the life of mass flow body.

The utility model provides a flexible composite current collector, flexible composite current collector include metal grid substrate and combined material, and the combined material coating is on the two surfaces of metal grid substrate to fill the grid hole, combined material includes high molecular polymer and conducting agent.

That is, the flexible composite current collector includes a metal grid substrate and a composite material, the metal grid substrate has two surfaces which are oppositely arranged, and grid holes which penetrate through the two surfaces, the composite material is coated on the two surfaces of the metal grid substrate and fills the grid holes, and the composite material includes a high molecular polymer and a conductive agent.

The metal grid substrate is a substrate made of metal material, and the shape of the metal grid substrate can be a sheet, has a preset thickness, and is provided with grid holes to form a structure similar to a net.

The metal material may be aluminum, copper or nickel, and is not particularly limited, for example, when the flexible composite current collector is used for the positive electrode, the positive electrode may be made of metal aluminum, and when the flexible composite current collector is used for the negative electrode, the negative electrode may be made of metal aluminum, copper or nickel.

Composite materials refer to materials having new properties formed by mixing two or more materials.

The high molecular weight polymer is a high molecular weight compound formed by repeating a bond.

The conductive agent is a substance having a conductive effect, for example, in order to ensure that the electrode has good charge and discharge performance, a certain amount of conductive substance is usually added during the manufacturing of the pole piece, and the conductive agent plays a role in collecting micro-current between active substances and between the active substances and a current collector, so as to reduce the contact resistance of the electrode to accelerate the movement rate of electrons, and simultaneously, the migration rate of lithium ions in the electrode material can be effectively improved, thereby improving the charge and discharge efficiency of the electrode.

The flexible composite current collector is used for improving the flexibility of the current collector, improving the service performance of the current collector and prolonging the service life of the current collector. As shown in fig. 4 or 7, the flexible composite current collector includes a metal grid substrate and a composite material coated on the metal grid substrate, the flexible composite current collector includes a metal grid substrate 100 and a composite material 40 coated on both surfaces of the metal grid substrate 100 and filling grid holes 10, the composite material includes a high molecular polymer and a conductive agent, on one hand, the metal grid substrate has a light weight characteristic, and on the other hand, the metal grid substrate has a good flexibility, the composite material is coated on both surfaces of the metal grid substrate and fills the grid holes, so that when the flexible composite current collector is applied to a battery, slurry is prevented from leaking out of the grid holes, and the composite material includes a high molecular polymer and a conductive agent, the conductive agent is bonded to the metal grid substrate through the high molecular polymer, and the conductive agent is connected to each other and to the conductive metal structure, so that a good network is formed in the flexible composite current collector. Based on the characteristics of excellent flexibility, conductivity, light weight and the like of the flexible composite current collector, the service performance of the flexible composite current collector can be effectively improved.

It can be understood that the high molecular polymer has flexibility, and is coated on the metal grid substrate through the flexible high molecular polymer, and the high molecular polymer is coated on two surfaces of the metal grid substrate, so that the flexibility of the whole flexible composite current collector is further improved.

The traditional base material adopts metal foil, has heavier mass and limited elongation rate, adopts the base material as a pole piece, is easy to demould after an anode membrane or a cathode membrane expands, and the pole piece is easy to crack due to expansion after the battery is used, for example, the decomposition of electrolyte can cause the gas generation of the lithium ion battery in the circulation process, the gas generation not only can cause the swelling and deformation of the lithium ion battery, but also can cause the loose joint between the pole pieces of the lithium ion battery, the performance degradation of the lithium ion battery is caused, and the generated gas can only be spread in the interlayer gap, so the exhaust efficiency is lower.

It is understood that when a lithium battery is charged and discharged, current flowing through the current collector generates heat, which increases the temperature of the battery. The battery core is mainly composed of a positive electrode material, a negative electrode material, electrolyte, a diaphragm and a shell, the battery core expansion can cause risks such as pole piece demoulding and pole piece crack, and more seriously, the diaphragm can shrink and even decompose to influence safety performance. The utility model provides a flexible composite current collector still has carminative function, and high molecular polymer has the hole, and gaseous accessible corresponding hole is discharged, for example, the other high molecular polymer that can fill in the mesh through metal substrate that produce diffuses, makes the exhaust capacity improve greatly, improves electric core performance to avoid electric core inflation and a series of problems that cause. For example, the pore size of the high molecular polymer is 100nm.

Electrolyte in the battery is used for transferring anions and cations in the anode material and the cathode material, the current collector has better wettability on the electrolyte, and the current collector has larger area in contact with ions, so that the quick transfer of electrons is facilitated.

It can be understood that the electrolyte can be diffused through the high molecular polymer filled in the grid holes of the metal grid substrate, so that the wetting capacity of the electrolyte is greatly improved, and the transmission efficiency of electrons is improved.

It can be further understood that the thickness of the metal grid base material is equivalent to that of the traditional base material, the base material can greatly reduce the weight, and the energy density of the battery cell is improved; and because the surface of the metal grid base material is a mixture of high-molecular polymer and conductive particles, the conductive particles on the surface of the metal grid base material can provide anchor nodes for high molecules in cathode materials or anode materials, and compared with the smooth surface of a metal foil, the battery membrane based on the flexible composite current collector has stronger adhesive force, and the demoulding problem can be effectively improved.

Further, the opposite ends of the metal grid substrate are provided with tabs.

The two opposite ends of the metal grid substrate mean that the metal grid substrate extends along a certain direction and has a certain length or width, and the two opposite ends can be two ends in the length direction or two ends in the width direction.

The tab, the battery is divided into positive and negative electrodes, the tab is a metal conductor leading the positive and negative electrodes out from the battery core, and the ears of the positive and negative electrodes of the battery are contact points during charging and discharging.

As shown in fig. 4 and 7, the tabs 30 are disposed at two opposite ends of the metal grid substrate 100, so that the flexible composite current collector is conveniently applied to a battery, and the electrical conduction between the battery core inside the battery and an external circuit structure is realized.

It can be understood that, furthermore, the tab is not coated with a composite material, on one hand, the energy density of the tab is improved, and on the other hand, the tab is coated with the composite material, which results in poor overcurrent capacity, and the tab is welded, and the polymer is inconvenient to weld, so that the tab is preferably not coated with the composite material. Of course, whether to coat the tab with the composite material may also be designed according to needs in a specific application process, and is not limited specifically herein.

Further, the metal grid base material is defined to have a length direction and a width direction, and the lugs are arranged at two ends of the width direction; the pole ear is a metal sheet.

Sheet metal refers to a sheet-like structure made of a metallic material.

As shown in fig. 4 and 7, it can be understood that, considering that the flexible composite current collector is generally rolled along the length direction during the rolling process, the tabs are disposed at both ends of the width direction, and after the flexible composite current collector is rolled along the length direction, the tabs protrude from both ends of the rolled flexible composite current collector. Of course, if the flexible composite current collector needs to be rolled along the width direction, the tabs can be arranged at two ends of the length direction.

Compared with the lug with the net structure, the lug with the metal sheet shape has larger surface area and better current overcurrent capability, and the lug is the metal sheet in order to improve the current overcurrent capability.

Furthermore, grid holes are formed in the metal sheet.

And/or the width of the pole ear is 5mm-50mm.

And/or the metal base material and the tab are of an integrated structure.

The integral forming means that the integral forming is processed by a whole blank material.

Because the weight energy density of the metal sheet with the net-shaped structure is higher, under some scenes, grid holes can be formed in the metal sheet, so that the lug is the metal sheet with the net-shaped structure, and the weight energy density of the battery is improved.

The width of the pole lug can influence the overcurrent capacity and the weight energy density, the width of the pole lug is 5mm-50mm in the application, and the width of the pole lug can be set to be 5mm, 10mm, 20mm, 30mm, 40mm and 50mm according to requirements. For example, a larger width of the tab region (30 mm-50 mm) results in a higher tab height, lower gravimetric energy density and better current capacity, whereas a smaller width of the tab region (5 mm-30 mm) results in a lower tab height, higher gravimetric energy density and poorer current capacity.

In order to improve the overall performance of the flexible composite current collector and avoid the tab from breaking and falling off from the metal grid substrate, the metal grid substrate and the tab are of an integrally formed structure, namely, the tab is formed by extending from the end part of the metal grid substrate, and the tab and the metal grid substrate are of an integral structure.

In some cases, the tab and the metal grid substrate are separated and combined by welding or other connecting means, which is not limited herein.

Further, the metal grid substrate comprises a plurality of metal wires, and the plurality of metal wires are arranged in a crossed mode.

The metal wire refers to a strip structure in a line shape, and may be a metal wire, for example.

In order to form the metal grid substrate with a net-shaped structure, the metal grid substrate can be formed by a metal wire weaving method, punching holes in the whole metal sheet, and forming grid holes in the metal sheet by etching, and in any way, the finally presented structure is similar to the crossing arrangement of a plurality of metal wires to form the metal grid substrate.

It will be appreciated that the metal grid substrate needs to be rolled for a first time before forming, the denser and coarser the wires are before rolling (e.g. wire diameter >100 μm), the larger the area fraction of the wires in the substrate after rolling, the smaller the metal grid, the better the flow capacity and the lower the gravimetric energy density. Conversely, the more sparse and thinner the wire (e.g., wire diameter <100 μm), the smaller the area fraction of the wire in the substrate after rolling, the larger the metal mesh, the poorer the current capacity, and the higher the gravimetric energy density. Before forming the metal grid substrate, a material of metal wires of a suitable diameter size may be selected to prepare a metal grid substrate of a suitable mesh size, e.g. 100 μm metal wires before rolling are pressed to a thickness of around 10 μm.

It is understood that the size of the metal mesh can be adjusted by the density and thickness of the metal wires in the metal grid substrate before rolling, under the condition that the target thickness of the metal grid substrate after rolling is determined. Under the condition that the target thickness of the metal grid base material after rolling is determined, the density and the thickness of metal wires in the metal grid base material before rolling can be adjusted according to the requirements of overflowing and energy density. Here, the density and thickness of the wire before the rolling are not limited, and may be specifically selected according to actual needs.

Further, the metal grid substrate is of an integrally formed structure.

And/or the shape of the grid holes comprises rhombic holes, square holes, rectangular holes or wavy holes.

And/or defining the area of the metal grid base material as S1, and the sum of the areas of the grid holes on the metal grid base material as S2, wherein S2: the range of S1 is 40-70%.

In order to improve the overall performance of the metal grid substrate, the metal grid substrate is of an integrally formed structure, that is, the metal grid substrate with a net-shaped structure is formed by punching holes on the whole metal sheet, or meshes are formed on the metal sheet in an etching mode.

In order to further improve the ductility of the metal grid base material with a net structure and change the shape of the grid holes, flexible metal grid base materials with different ductility characteristics can be obtained, for example, the grid holes can be rhombic holes, square holes, rectangular holes or wavy holes, wherein the rhombic holes are preferred, and the ductility is better. Possess the metal grid substrate of the good network structure of ductility, the combined material of high-molecular polymer and conducting agent further coats on it, obtain flexible composite current collector, make the flexible composite current collector that obtains have good ductility, make flexible composite current collector have fabulous ductility in mechanical motion's direction, for example, mechanical motion's direction can be along the direction of motion of length direction book flexible composite current collector, in the book system in-process, because fabulous ductility, flexible composite current collector is difficult for breaking, because its fabulous ductility, when using flexible composite current collector in the battery, under the condition that produces a certain amount of gas in the electric core, certain inflation condition takes place for the electric core, because the ductility, avoid appearing pole piece crack phenomenon.

It will be appreciated that the undulating apertures are such that the wires surrounding the apertures forming the grid are undulating, thereby forming undulating apertures.

Further, defining the maximum width of the grid holes as D, then: d is more than 0mm and less than or equal to 5mm.

And/or, defining the thickness of the metal grid substrate as H1, and satisfying the following conditions: h1 is more than or equal to 5 mu m and less than or equal to 100 mu m.

And/or defining the thickness of the flexible composite current collector as H2, and satisfying the following conditions: h2 is more than or equal to 10 mu m and less than or equal to 300 mu m.

Considering that the larger the grid hole is, the polymer is difficult to spread and coat at the grid hole, easily leads to leaking the material, therefore, the maximum width of defining the grid hole is D, then satisfies: d is more than 0mm and less than or equal to 5mm, namely, the maximum width of the grid holes D can be 1mm, 2mm, 3mm, 4mm and 5mm, and is specifically set according to the requirement.

Generally, the surface of a directly purchased or manufactured metal material may have defects such as unevenness and burrs, for example, a directly purchased metal mesh is used as a raw material for manufacturing a metal grid substrate, the metal mesh may be regarded as being formed by a plurality of metal wires which are mutually crossed, the metal wires may be regarded as being similar to a cylinder, the metal wires may have different thicknesses, and if the directly purchased metal mesh is used for manufacturing a flexible composite current collector, a problem of great product quality difference may occur. Therefore, before the metal mesh is changed into the metal grid substrate, a first rolling is needed to flatten the metal mesh to obtain a net-shaped thin metal grid substrate with uniform thickness, the thickness of the metal grid substrate is defined as H1, and the thickness of the metal grid substrate is selected to be in a range of H1 being more than or equal to 5 μm and less than or equal to 100 μm so as to facilitate the subsequent coating of the composite material on the metal grid substrate, and the thickness of the metal grid substrate is H1 which can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm and 100 μm.

Of course, the first rolling is preferably performed, and the first rolling may not be performed, and may be selected according to the circumstances. In addition, if the purchased or obtained metal mesh has the characteristic of uniform thickness, the metal mesh can also be directly used as a metal grid substrate to prepare the flexible composite current collector.

After obtaining the metal grid substrate, need coat combined material on the metal grid substrate, in order to make combined material well cladding on the metal grid substrate, and realize the fine pliability and the performance of the flexible compound mass flow body, the thickness of the flexible compound mass flow body of definition is H2, then satisfies: h2 is more than or equal to 10 mu m and less than or equal to 300 mu m, namely, the composite material is coated on the metal grid substrate, after the composite material is dried and rolled for the second time, the thickness H2 of the obtained flexible composite current collector meets the condition that H2 is more than or equal to 10 mu m and less than or equal to 300 mu m, and H2 can be 10 mu m, 20 mu m, 30 mu m, 40 mu m, 50 mu m, 60 mu m, 70 mu m, 80 mu m, 90 mu m, 100 mu m, 150, 200 mu m, 250 mu m and 300 mu m.

The preferable scheme of the second rolling is to make the distribution of the coated composite material uniform, and of course, the second rolling may not be performed and is selected according to the specific situation. In addition, when the composite material is coated, the effect of uniform distribution of the composite material can be achieved, and secondary rolling is not needed.

Further, the ratio of the high molecular polymer to the conductive agent is (100.

The high molecular polymer includes a water-insoluble high molecular polymer or an oil-insoluble high molecular polymer.

The water-insoluble high molecular polymer means that the high molecular polymer is insoluble in water; the term "oil-insoluble high-molecular polymer" means that the high-molecular polymer is insoluble in oily substances.

The conductive agent comprises at least one of carbon nano tube, graphene, graphite, carbon fiber, carbon black and metal powder.

The shape of the conductive agent is one or more of granular shape, linear shape and sheet shape.

When the flexible composite current collector is applied to a battery, the flexible composite current collector is used for bearing a cathode material and an anode material and needs to be in contact with an electrolyte, some substances possibly existing in the cathode material, the anode material and the electrolyte can dissolve a high molecular polymer to cause material leakage, in order to avoid the phenomenon, the high molecular polymer adopts a non-water-soluble high molecular polymer for aqueous cathode and anode slurry, namely, the high molecular polymer is not dissolved in an aqueous substance to avoid the dissolution of the high molecular polymer after the high molecular polymer is in contact with the aqueous material; for the oily cathode slurry and the oily anode slurry, the high molecular polymer adopts the non-oil-soluble high molecular polymer, namely the high molecular polymer is insoluble in oily substances, so that the high molecular polymer is prevented from being dissolved after contacting the oily materials.

Among them, the oil-insoluble high molecular polymer may preferably be insoluble in N-methylpyrrolidone (NMP).

The conductive agent is mainly used for conducting electricity, and the material with the conductive function can be selected according to needs, for example, at least one of carbon nanotubes, graphene, graphite, carbon fibers, carbon black and metal powder can be selected, that is, one of the conductive agents can be selected, or a mixture of two or more of the conductive agents can be selected, and the conductive agent is specifically selected according to needs.

The shape of the conductive agent is not limited, and may be the shape of the conductive agent itself, or a specific shape after processing, and specifically is not limited, and may be one or more of granular, linear, and sheet, that is, one of the shapes, or a mixture of a plurality of shapes, and is specifically selected according to the need.

Further, the water-insoluble high polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylate binder, styrene butadiene rubber, aramid, polyacrylonitrile, polyacrylic acid and polymethyl methacrylate.

The non-oil-soluble high molecular polymer comprises one or more of styrene butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, nitrile rubber and hydrogenated nitrile rubber.

For the aqueous cathode and anode slurry, the high molecular polymer is a water-insoluble high molecular polymer, and may be one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylate binder, styrene-butadiene rubber, aramid fiber, polyacrylonitrile, polyacrylic acid, and polymethyl methacrylate. For the oily cathode and anode slurry, the high molecular conductive substrate adopts a high molecular polymer which can not be dissolved by N-methyl pyrrolidone (NMP), for example, one or more of styrene butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, nitrile rubber and hydrogenated nitrile rubber, so as to prevent the solvent in the slurry from dissolving the high molecular polymer and causing the slurry leakage of the substrate.

The application still provides a pole piece, and the pole piece includes the mass flow body and sets up the active material on the mass flow body, and wherein, the mass flow body is the flexible compound mass flow body. Since the flexible composite current collector adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and details are not repeated herein.

For example, the electrode sheet may be a cathode electrode sheet or an anode electrode sheet, and when the electrode sheet is a cathode electrode sheet, the cathode material is disposed on the flexible composite current collector. When the pole piece is an anode pole piece, the anode material is arranged on the flexible composite current collector. The active material layer may also be formed on the side of the flexible composite current collector, and the position and manner of coating the active material on the flexible composite current collector are not particularly limited. The flexible composite current collector is applied to the pole piece, so that the bending performance of the pole piece is improved.

The present application also provides a battery, the battery comprising: the electrode comprises a cathode pole piece, an anode pole piece, an isolating film and electrolyte, wherein the cathode pole piece and/or the anode pole piece are the pole pieces. The flexible composite current collector is applied to the pole piece, so that the bending performance of the pole piece is improved, and the use safety of the battery is improved. The electrolyte solution contains one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, and the solute comprises LiPF ₆ 、LiBF ₄ 、LiBOB、LiAsF ₆ 、Li(CF ₃ SO ₂ ) ₂ N、LiCF ₃ SO ₃ 、LiClO ₄ One or more of them. The isolating membrane is selected from one or more of films with electrochemical stability and chemical stability, including polyethylene, polypropylene, non-woven fabrics and polyfibre materials. Since the pole piece adopts all the technical solutions of all the embodiments, at least all the beneficial effects brought by the technical solutions of the embodiments are achieved, and are not described in detail herein.

In order to solve the problems of electrode fracture and the like caused by long-term bending of the current collector, the patent with the application number of CN202011180900.0 discloses a flexible current collector and a preparation method thereof, a pole piece and a battery, the scheme uses a three-dimensional conductive framework as a substrate main body, the three-dimensional conductive framework needs to be sequentially subjected to acid washing, water washing, surface treatment of a silane coupling agent and drying, then is immersed into a polymer precursor solution, and is solidified after infiltration to obtain the flexible current collector, and the flexible current collector has the advantages of high substrate cost and processing cost and complex process, so that the industrial production cost is high.

The flexible composite current collector not only improves the flexibility of the current collector, enables the use performance of the current collector to be improved, prolongs the service life of the current collector, but also has the advantages of relatively low cost of the base material, simple process and wide application in industrial production.

As shown in fig. 1, the present application provides a method for preparing a flexible composite current collector, comprising the steps of: providing a metal grid substrate; coating composite materials on two surfaces of the metal grid base material, and filling grid holes in the metal grid base material to obtain the coated metal base material; and drying the metal substrate to obtain the flexible composite current collector.

The composite material is coated on two surfaces of the metal grid base material and is filled in the grid holes, so that when the flexible composite current collector is applied to a battery, slurry is prevented from leaking out of the grid holes, the coated metal base material is dried, the solvent is removed, and the composite material is firmly bonded on the metal base material. And the composite material comprises a high molecular polymer and a conductive agent, the conductive agent is bonded to the metal grid substrate through the high molecular polymer, and the conductive agents are connected with each other and communicated with the metal structure, so that an excellent conductive network is formed in the flexible composite current collector.

The method has the advantages of easily obtained raw materials, low cost and simple operation steps, and can be widely applied to industrial production.

Further, before the step of coating the composite material on both surfaces of the metal grid substrate, the method further comprises the following steps: and rolling the metal grid base material to obtain the rolled metal grid base material.

That is, in order to obtain a mesh-shaped thin metal grid substrate having a uniform thickness, the metal grid substrate is first rolled to obtain a rolled metal grid substrate, and as shown in fig. 8, the metal wire is flattened after being rolled, and the area of the flat surface is increased, and similarly, as shown in fig. 2 and 3 and fig. 5 and 6, the rolled metal grid substrate has a larger surface area on the flat surface after being flattened, thereby facilitating the coating of the composite material. And then coating composite materials on two surfaces of the rolled metal grid base material, so that the composite materials not only coat the surface of the metal grid base material, but also fill grid holes to obtain the coated metal base material.

Further, in the step of drying the metal substrate to obtain the flexible composite current collector, the method further comprises the following steps: and drying the metal base material, and rolling the dried metal base material to obtain the rolled metal base material.

The composite material at least comprises a high molecular polymer, a conductive agent and a solvent, wherein the solvent is used for uniformly mixing the high molecular polymer and the conductive agent and forming slurry with fluidity, so that the coating is convenient, the composite material has certain viscosity and fluidity, the problem of uneven coating of the composite material can exist in the process of coating the composite material, and in order to obtain a flexible composite current collector with thin thickness, flat surface, no slurry leakage, good conductivity and light weight, after the step of drying the metal substrate, secondary rolling is carried out, and the rolled flexible composite current collector is obtained.

Further, before the step of coating the composite material on the two surfaces of the metal grid substrate, the method also comprises the following steps: and reserving preset widths at two opposite ends of the metal grid substrate to form the tabs.

In order to conveniently prepare the tabs, preset widths are reserved at two opposite ends of the metal grid substrate directly to form the tabs, or the preset widths are reserved at two opposite ends of the metal grid substrate which is rolled for the first time directly to form the tabs, so that the subsequent need of further arranging the tabs on the metal grid substrate is avoided, and the tabs are part of the metal grid substrate, so that the tabs are connected on the metal grid substrate more firmly, and the tabs are not coated with a composite material. And preset widths are reserved at two opposite ends of the metal grid substrate directly after the first rolling so as to form the tabs, so that the tabs can conveniently form a structure with uniform thickness and smooth surface.

Further, in the step of providing a metal grid substrate, comprising: forming holes on the metal sheet to obtain a metal grid base material with holes; or reserving preset widths at the two opposite end parts of the metal sheet to form the lugs, and forming holes in the middle of the metal sheet to obtain the metal grid substrate.

The metal sheet is a sheet-like metal material, and no opening is formed on the surface.

The structure of the tab can affect the performance of the tab, and the tab with the metal net structure has higher weight energy density and poorer overcurrent capacity compared with the tab with the metal sheet structure under the condition of the same area, so that the tab with the metal net structure or the tab with the metal sheet structure can be selected and manufactured according to actual needs. For example, in the process of preparing the metal grid substrate, according to requirements, a preset width is reserved at two opposite ends of a metal sheet to form a tab, a hole is formed in the middle of the metal sheet to obtain a perforated metal grid substrate, and a tab with a metal sheet structure is obtained. In order to obtain a tab with a metal mesh structure, pores may be formed in the entire metal sheet so that the portion for forming the tab also has a mesh structure.

And the pole ear is of a smooth surface structure so as to improve the overcurrent performance.

The pore-forming method may be chemical etching pore-forming, or mechanical pore-forming, and is not particularly limited.

Further, in the step of providing a metal grid substrate, comprising: providing a plurality of metal wires, and arranging the plurality of metal wires in a mutually crossed manner to form the metal grid base material.

That is, the metal grid base material may be formed by weaving a plurality of metal wires to be crossed with each other.

It can be understood that the flexible composite current collector obtains the flexible pole piece through the processes of coating, cold pressing, slitting and die cutting, the flexible pole piece is wound or laminated to obtain a bare cell, and the flexible pole piece is assembled, injected, formed and the like to the battery using the flexible base material. Because the pole piece has better flexibility and overcurrent capacity, the lithium battery has better application scenes on high-silicon batteries and wearable equipment besides being used for conventional lithium batteries.

Example 1

Preparing a metal grid base material, wherein the metal grid base material comprises a plurality of metal wires which are mutually crossed, the metal wires are mutually crossed to form a net-shaped porous metal grid base material, the metal wires can be regarded as a cylinder-like shape, the diameter of the metal wires is 40 mu m, then, carrying out first rolling on the metal grid base material to obtain the rolled metal grid base material, and the rolled metal grid base material has the characteristics of uniform thickness and large specific surface area, and the thickness of the rolled metal grid base material is 5 mu m; coating composite materials on two surfaces of the rolled metal grid base material, and filling grid holes to obtain the coated metal grid base material; and drying the coated metal grid substrate, and performing secondary rolling to obtain a flexible composite current collector with good flexibility, small thickness, flat surface, no slurry leakage during coating, good conductivity and light weight, wherein the thickness of the flexible composite current collector is 10 micrometers.

And then processing the flexible composite current collector, obtaining a flexible pole piece through the processes of coating, cold pressing, slitting and die cutting, obtaining a bare cell by winding or laminating the flexible pole piece, and obtaining the battery using the flexible base material through the processes of assembling, injecting liquid, forming and the like. Because the pole piece has better flexibility, the pole piece has better application scenes on high-silicon batteries and wearable equipment besides being used for conventional lithium batteries.

The composite material includes, among other things, a high molecular polymer (e.g., polyvinylidene fluoride) and a conductive agent (e.g., carbon nanotubes). The dosage ratio of the high molecular polymer (polyvinylidene fluoride) to the conductive agent (carbon nano tube) is 1:10. the shape of the opening is rhombic. Reserve the width in the width direction of metal grid substrate and form utmost point ear portion, the width of utmost point ear is 20mm, and utmost point ear portion is the network structure who has the trompil.

The area of the metal grid base material is S1, the sum of the areas of the openings on the metal grid base material is S2, and then S2: the range of S1 is 40%.

Example 2

On the basis of embodiment 1, under the condition that other conditions are not changed, the structure of the tab part is changed into a metal sheet structure from a net-shaped tab.

Example 3 to example 12

On the basis of example 1, the parameters were adjusted to obtain examples 3 to 12.

Examples 3 and 4 in example 1, the thickness after the first rolling and the thickness after the second rolling were changed by changing the diameter of the wire under otherwise unchanged conditions.

Examples 5 and 6 the specific weight of the high molecular weight polymer and the conductive agent was changed without changing other conditions based on example 1.

Examples 7 and 8 on the basis of example 1, the width of the tab was changed without changing other conditions.

Examples 9 and 10 in addition to example 1, the ratio of the sum S2 of the areas of the openings in the metal grid substrate to the area S1 of the metal grid substrate was changed without changing other conditions.

Example 11 in addition to example 1, the kind of the high molecular weight polymer was changed without changing other conditions.

Example 12 the kind of the conductive agent was changed without changing other conditions on the basis of example 1.

Comparative example 13

The method comprises the following steps of processing a metal sheet-shaped current collector, obtaining a pole piece through the processes of coating, cold pressing, slitting and die cutting, obtaining a bare cell by winding or laminating the pole piece, and obtaining the battery through the processes of assembling, injecting liquid, forming and the like.

Table 1 parameter table for preparing flexible composite current collector

Table 2 parameter table for preparing flexible composite current collector

Table 3 flexible composite current collector test examples

The pole pieces prepared in examples 1 to 12 and comparative example 13 were subjected to performance tests to obtain parameters, and the test method and the steps of each parameter were as follows:

(1) Pole piece adhesion

Cutting the pole piece, wherein the width of the pole piece is 2cm, the height of the pole piece is 10cm, one end of the pole piece is firmly bonded with a steel plate of a tensile testing machine by adopting double faced adhesive tape, the other end of the pole piece is clamped by a clamp, the pole piece is vertically unfolded, and a tensile test is carried out until the pole piece is completely peeled off from the steel plate, so that the tensile value is the pole piece bonding force.

(2) Over-current capability

Charging the battery at constant temperature of 25 ℃ for 0.5C/1C, and recording the temperature change of the battery in the charging and discharging process; the lower the battery charging temperature rise, the higher the overcurrent capability.

(3) Cycle performance test

And (3) carrying out 0.5C charging/1C discharging circulation on the battery at a constant temperature of 25 ℃, and recording the capacity retention rate and the corresponding cycle number of the battery in the circulation test process.

From the above experimental data, it can be seen that the experimental results and data of the comparative examples 1 and 2 show that the variables of the example 2 are the structure of the tab compared to the example 1, the structure of the tab used in the example 1 is a net structure, the structure of the tab used in the example 2 is a metal sheet structure, and the pole piece obtained in the example 2 has better pole piece adhesion and overcurrent capacity than the pole piece obtained in the example 1.

Examples 3 and 4, based on example 1, the diameter of the wire was changed under the same conditions, and it can be seen from experimental data that under certain conditions, as the thickness of the wire before the first rolling is larger, the thicker the thickness of the obtained metal substrate after the first rolling is, the better the flow capacity of the pole piece is.

Examples 5 and 6 the specific weight of the high molecular weight polymer and the conductive agent was changed without changing other conditions based on example 1. According to experimental data, under a certain condition, the more the conductive agent is used, the better the overcurrent capacity is, and the more the high-molecular polymer is used, the better the pole piece bonding force is.

Examples 7 and 8 the width of the tab was changed without changing other conditions on the basis of example 1. According to experimental data, the wider the tab is, the better the overcurrent capacity of the pole piece is under certain conditions.

Examples 9 and 10 the ratio of the sum S2 of the areas of the openings in the metal base material to the area S1 of the metal base material was varied in addition to example 1, with other conditions being unchanged. From experimental data, it is known that under a certain condition, as the sum S2 of the areas of the openings on the metal base material is larger, the overcurrent capacity is poorer, and the pole piece adhesion of the pole piece is also poorer.

Example 11 in addition to example 1, the kind of the high molecular weight polymer was changed without changing other conditions. According to experimental data, the variety of the high molecular polymer is changed under certain conditions, so that the influence on the pole piece bonding force of the pole piece is large, and the influence is mainly determined by the performance of the high molecular polymer.

Example 12 the kind of the conductive agent was changed without changing other conditions on the basis of example 1. According to experimental data, under a certain condition, the change of the type of the conductive agent influences the pole piece adhesion force and the overcurrent capacity of the pole piece.

It can be seen from the data of example 2 and comparative example 13 that, under the condition that other conditions are not changed, the tab of metal grid substrate + the tab of metal sheet is adopted in example 2, and the tab of metal sheet substrate + the tab of metal sheet is adopted in comparative example 13, and it can be seen from the experimental data that the overcurrent capacity of example 2 is superior to that of comparative example 13, and although the conductive area of the metal grid substrate is smaller than that of the metal sheet, the tab of metal sheet is arranged on the metal grid substrate, which is helpful for improving the overcurrent capacity.

The above is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the specification and the drawings, or any other related technical fields directly/indirectly using the inventive concept are included in the scope of the present invention.

Claims

1. A flexible composite current collector, comprising:

a metal grid substrate; and

the composite material is coated on two surfaces of the metal grid base material and fills grid holes, and the composite material comprises a high molecular polymer and a conductive agent.

2. The flexible composite current collector of claim 1, wherein the metal grid substrate is provided with tabs at opposite ends.

3. The flexible composite current collector of claim 2, wherein the metal grid substrate is defined to have a length direction and a width direction, wherein the tabs are disposed at both ends of the width direction, and wherein the tabs are metal sheets.

4. The flexible composite current collector of claim 3, wherein the grid apertures are formed in the metal sheet;

and/or the width of the tab is 5mm-50mm;

and/or the metal grid substrate and the lug are of an integrally formed structure.

5. The flexible composite current collector of claim 1, wherein the metal grid substrate comprises a plurality of metal wires, the plurality of metal wires being arranged in a cross.

6. The flexible composite current collector of claim 5, wherein the metal grid substrate is an integrally formed structure;

7. The flexible composite current collector of claim 5, wherein a maximum width of the grid apertures, D, is defined to satisfy: d is more than 0mm and less than or equal to 5mm;

8. The flexible composite current collector as claimed in any one of claims 1 to 7 wherein the ratio of the high molecular polymer to the conductive agent is (100;

9. The flexible composite current collector of claim 8, wherein the non-water soluble high polymer comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylate type binders, styrene butadiene rubber, aramid, polyacrylonitrile, polyacrylic acid, polymethyl methacrylate;

10. A pole piece comprising a current collector and an active material disposed on the current collector, wherein the current collector is the flexible composite current collector of any one of claims 1 to 9.

11. A battery, comprising: a cathode plate, an anode plate, a separator and an electrolyte, wherein the cathode plate and/or the anode plate is the plate of claim 10.

12. The preparation method of the flexible composite current collector is characterized by comprising the following steps of:

providing a metal grid substrate;

and drying the metal substrate to obtain the flexible composite current collector.

13. The method of preparing a flexible composite current collector of claim 12, further comprising, prior to the step of coating both surfaces of the metal grid substrate with the composite material, the steps of:

14. The method of manufacturing a flexible composite current collector of claim 12, wherein the step of drying the metal substrate to obtain the flexible composite current collector comprises the steps of:

and drying the metal base material, and rolling the dried metal base material to obtain the rolled flexible composite current collector.

15. The method of preparing a flexible composite current collector of any of claims 12 to 14, further comprising, before the step of coating both surfaces of the metal grid substrate with a composite material, the steps of:

16. The method of preparing a flexible composite current collector of any of claims 12 to 15, wherein in the step of providing a metal grid substrate, comprising:

forming holes on a metal sheet to obtain the metal grid substrate;

or reserving preset widths at the two opposite end parts of the metal sheet to form the lugs, and forming holes in the middle of the metal sheet to obtain the metal grid substrate.

17. The method of preparing a flexible composite current collector of any of claims 12 to 15, wherein in the step of providing a metal grid substrate, comprising: