CN112510208A - Folding graphene current collector, preparation method thereof and lithium ion battery - Google Patents

Folding graphene current collector, preparation method thereof and lithium ion battery Download PDF

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CN112510208A
CN112510208A CN202011357990.6A CN202011357990A CN112510208A CN 112510208 A CN112510208 A CN 112510208A CN 202011357990 A CN202011357990 A CN 202011357990A CN 112510208 A CN112510208 A CN 112510208A
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current collector
coating
area
graphene
battery
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CN112510208B (en
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黄汉川
陈冬
陈建
王羽平
相佳媛
吴贤章
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Zhejiang Narada Power Source Co Ltd
Hangzhou Nandu Power Technology Co Ltd
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Zhejiang Narada Power Source Co Ltd
Hangzhou Nandu Power Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/72—Grids
    • H01M4/74—Meshes or woven material; Expanded metal
    • H01M4/747—Woven material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

The invention relates to a folding graphene current collector, a preparation method and a lithium ion battery, wherein the folding graphene current collector is used for improving the resistance of a pole piece, reducing the internal resistance of the battery, improving the contact area ratio of a current collector and an active substance, improving the specific energy density of the battery and reducing the cost of the battery; meanwhile, conducting modification treatment is carried out on the surface of the braided current collector; the contact area and the binding force of the active substance and the current collector are improved from the two aspects, and the resistance of the pole piece is improved, so that the internal resistance of the battery is greatly reduced; meanwhile, the use amount of the foil, the conductive agent and the binding agent is reduced, the specific energy density of the battery is improved, and the cost of the battery is reduced.

Description

Folding graphene current collector, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the field of lithium ion batteries, relates to a current collector and a lithium ion battery, and particularly relates to a folding graphene current collector, a preparation method thereof and a lithium ion battery, wherein the folding graphene current collector is used for improving the resistance of a pole piece, reducing the internal resistance of the battery, improving the contact area ratio of the current collector and an active substance, improving the specific energy density of the battery and reducing the cost of the battery.
Background
With the rapid development of human society, a large amount of natural resources are developed and used, so that problems such as resource shortage and environmental pollution inevitably occur, and in order to solve the problem, the problems such as energy shortage and environmental pollution are alleviated, and the new energy industry is rapidly developed. The lithium ion battery has the advantages of high energy density, long cycle life, good safety and stability, no memory effect, environmental friendliness and the like, so that the lithium ion battery is widely applied to the fields of electric new energy automobiles, consumer electronics and energy storage. In recent years, the electric automobile industry is rapidly developed due to guidance and demand of governments and markets, and the demand of lithium ion batteries is greatly increased, so that the lithium ion battery industry is rapidly developed. At present, people have higher and higher requirements on the energy density of lithium ion batteries, and therefore, how to improve the energy density of the lithium ion batteries is an important challenge to be faced by researchers in the lithium battery industry.
The foil material for the lithium ion battery is mainly copper foil or aluminum foil, and the current collector is used for rapidly transferring electrons, so that the performance of the battery is determined by the binding force and the contact area of the current collector and an active substance. Meanwhile, in order to improve the conductive capability of the active material, various conductive agents such as graphene, carbon black, graphite and the like are added.
The current collectors used by the current lithium ion battery are usually a light foil current collector and a coating current collector, the two current collectors have poor bonding performance with an active substance, and the electron transfer resistance between the active substance and the current collectors is large; in order to solve the binding power, the usage amount of the active matter binding agent is large, the conductivity of the active matter is reduced, the internal resistance of the battery is improved, and in order to improve the conductivity of the material, various conductive agents are added, so that the specific energy density of the battery is reduced; meanwhile, the application cost of the current collector in the lithium battery is high, and the price competitive advantage of the battery is hindered.
Disclosure of Invention
The invention aims to overcome the defects that the existing current collector is high in cost and the contact area of the current collector and an active substance is limited, and provides a folding graphene current collector which is capable of improving the resistance of a pole piece, reducing the internal resistance of a battery, improving the contact area ratio of the current collector and the active substance, improving the specific energy density of the battery and reducing the cost of the battery.
The second purpose of the invention is to provide a preparation method of the folded graphene current collector.
The third purpose of the invention is to provide the lithium ion battery containing the current collector.
In order to achieve the purpose, the invention adopts the following technical scheme:
a folding graphene current collector comprises a coating current collector and a woven current collector combined with the coating current collector; the coating current collector is provided with a coating part, a non-coating part and a lug part; wherein the non-woven portion is secured to the non-coated portion.
As a preferable aspect of the present invention, the knitted parts include a second knitted part and two first knitted parts having the same area; the non-woven parts are positioned on two sides of the second woven part, and the first woven part is positioned on one side of one non-woven part, which is far away from the second woven part; or the first weaving part and the non-weaving part are symmetrically arranged at two sides of the second weaving part.
In a preferred embodiment of the present invention, the coated portion has the same area as the second woven portion, the non-woven portion has the same area as the uncoated portion, and the first woven portion has an area equal to the sum of the areas of the non-woven portion and the second woven portion.
A preparation method of a folded graphene current collector comprises the following steps:
1) preparing a braided current collector: selecting metal wires with the diameter of R and aluminum foils with the length, width and height of m X n X h, weaving the metal wires and the aluminum foils into a net structure with the length of a and the width of b, and marking the net structure as a current collector X1; firstly, spraying a graphene solution on the surface of X1, and drying to obtain a current collector X2; then, drying the X2 in a conductive fiber silk solution atomization area to obtain a current collector X3;
2) preparing a coating current collector, marked as Y, wherein the coating is made of graphite; welding the non-woven part of the X3 obtained in the step 1) and the non-coating part of the Y to obtain a foldable graphene current collector, and recording as Z; wherein Y is one layer, and the number of X3 layers is 1-100 layers;
3) preparing active material slurry of the lithium ion battery, coating a layer of active material on the area A of the current collector Z obtained in the step 2), folding and embedding the area B of the current collector Z into the active material, and coating a layer of active material; wherein the area B of the current collector Z is in unilateral distribution or bilateral distribution, the number is 1-100, and the number of times of coating the active substance is two times more than the number of the area B of the current collector Z.
The area A of the current collector Z is the sum of the non-coating part and the coating part of the current collector Y and the non-weaving part and the second weaving part of the woven current collector X3, and the area B of the current collector Z is one of the first weaving parts of the current collector X3.
As a preferable scheme of the invention, in the step 1), R is 0.005-1mm, and a is 0.01-100 mm; b is 0.01-100mm, m is more than or equal to 1000mm, n is 10-100mm, and h is 0.005-1 mm.
In a preferred embodiment of the present invention, in step 1), the conductive fiber filaments have a length of 0.001 to 30mm and a diameter of 0.000001 to 0.1 mm. The conductive fiber yarn includes a metal fiber, a carbon black fiber, a conductive metal compound fiber, and a conductive polymer fiber, and a carbon fiber yarn is preferable in the present invention.
In a preferable embodiment of the invention, in the step 1), graphene slurry with a solid content of 3% to 8% is sprayed on the surface of the weaving part of the X1.
As a preferred embodiment of the present invention, X2 is passed through an atomization zone containing 3-8% of a solution of conductive filaments.
A lithium ion battery comprises the folding graphene current collector.
As a preferred scheme of the present invention, the preparation method of the lithium ion battery comprises: coating the positive pole slurry on a coating part A of a current collector Z for the first time by using an extrusion coating machine, then folding and flatly laying a weaving part B of the Z on the coating part A, coating the positive pole slurry for the second time by using a second extrusion coating machine, folding and flatly laying the weaving part B on the other side on the coating part A, repeating the steps for multiple times, drying the coating part A by using a drying tunnel, turning over the coating part A for the same operation, and rolling and slicing the coating part B to obtain a positive pole piece capable of assembling the battery; and assembling the positive pole piece, the diaphragm, the negative pole piece, the aluminum plastic film, the tab and the electrolyte into the battery.
The positive electrode slurry used is a positive electrode slurry used in the conventional art, such as a positive electrode LFP: (carbon black + graphene): PVDF 94: (1+1): 4, preparing the anode slurry; the negative electrode slurry used by the negative electrode plate is the negative electrode slurry used by the conventional process, such as graphite: PVDF 96: 4, preparing the negative electrode slurry according to the formula.
Compared with the prior art, the invention has the following beneficial effects:
1) the foldable graphene current collector can improve the contact area ratio and the binding force between the current collector and an active substance;
2) the pole piece manufactured by the folding graphene current collector greatly reduces the resistance of the pole piece, reduces the integral internal resistance of the battery and improves the multiplying power performance of the battery;
3) the folding graphene current collector disclosed by the invention has the advantages that the use amounts of foil, a conductive agent and an additive are reduced, the specific energy density of a battery is improved, and the cost of the battery is optimized.
Drawings
Fig. 1 is a schematic diagram of the bilateral structure of the braided current collector of the present invention.
Fig. 2 is a schematic view of a coated current collector of the present invention.
Fig. 3 is a schematic view of a foldable graphene current collector according to the present invention.
Fig. 4 is a front view of fig. 3.
FIG. 5 is a flow chart of the preparation of the present invention.
FIG. 6 shows a positive electrode plate prepared according to the present invention.
Fig. 7 is a schematic view of the single-sided structure of the braided current collector of the present invention.
In the figure, 11, a first knitted portion; 12. a second knitting portion; 2. a non-woven part; 3. a coating portion; 4. a non-coating portion; 5. the pole ear part.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are 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.
Referring to fig. 1 and 7, the knitted current collector X3 of the present invention has two non-knitted portions 2 (preferably aluminum foil), two first knitted portions 11 (preferably aluminum wires), and a second knitted portion 12 (preferably aluminum wires), wherein the area of the first knitted portion 11 is the same as the area of the two non-knitted portions 2 plus the second knitted portion 12. The non-woven parts 2 are positioned at two sides of the second woven part 12, the first woven part 11 is positioned at one side of one non-woven part 2 far away from the second woven part 12, namely the first woven part 11, the non-woven part 2, the second woven part 12 and the non-woven part 2 form a single-side structure in sequence, and the single-side structure is shown in fig. 7; alternatively, the first knitted portion 11 and the non-knitted portion 2 are symmetrically disposed on both sides of the second knitted portion 12, that is, the knitted current collector formed by the first knitted portion 11, the non-knitted portion 2, the second knitted portion 12, the non-knitted portion 2 and the first knitted portion 11 in this order forms a double-sided structure, as shown in fig. 1.
Referring to fig. 2, the coated current collector Y of the present invention has tab portions 5, a coated portion 3 and an uncoated portion 4, the uncoated portion 4 being disposed at both sides of the coated portion 3; the area of the non-woven part 2 is the same as that of the non-coated part 4.
Referring to fig. 3 and 4, the folded graphene current collector Z of the present invention is obtained by fixing the non-woven part 2 of the woven current collector X3 and the non-coated part 4 of the coated current collector Y, and the current collector Z is divided into an area a and an area B, where the area a is the sum of the non-coated part 4 and the coated part 3 of the current collector Y, plus the non-woven part 2 and the second woven part 12 of the woven current collector X3, and the area B of the current collector Z is one of the first woven parts 11 of the current collector X3.
Referring to fig. 5, the present invention provides a method for preparing a folded graphene current collector, including the following steps:
1) preparing a braided current collector: selecting metal wires with the diameter of R and aluminum foils with the length, width and height of m X n X h, weaving the metal wires and the aluminum foils into a net structure with the length of a and the width of b, and marking the net structure as a current collector X1; firstly, spraying a graphene solution on the surface of X1, and drying to obtain a current collector X2; then, drying the X2 in a conductive fiber silk solution atomization area to obtain a current collector X3;
2) preparing a coating current collector, marked as Y, wherein the coating is made of graphite; welding the non-woven part of the X3 obtained in the step 1) and the non-coating part of the Y to obtain a foldable graphene current collector, and recording as Z; wherein Y is one layer, and the number of X3 layers is 1-100 layers;
3) preparing active material slurry of the lithium ion battery, coating a layer of active material on the area A of the current collector Z obtained in the step 2), folding and embedding the area B of the current collector Z into the active material, and coating a layer of active material; wherein the area B of the current collector Z is in unilateral distribution or bilateral distribution, the number is 1-100, and the number of times of coating the active substance is two times more than the number of the area B of the current collector Z.
The graphene slurries used in examples 2 to 4 of the present invention were the same as those used in example 1; the graphite coatings used in examples 2-4 were the same as the graphite coating used in example 1.
Example 1
Selecting a double-sided coating aluminum foil with the thickness of 0.02mm, the length of 100000mm, the width of 300mm, the coating of graphite and the coating thickness of 0.0002mm, selecting an anode LFP: (carbon black + graphene): PVDF 94: (1+1): 4, preparing the positive pole piece with the length, width and thickness of 150mm by 150mm 0.2mm by coating, drying, rolling, slicing and other processes; selecting a smooth copper foil with the thickness of 0.01mm, the length of 100000mm and the width of 305mm, selecting negative graphite: PVDF 96: 4, coating, drying, rolling, slicing and the like to prepare a negative pole piece with the length and width of 152.5mm by 152 mm by 0.15mm, which can be used for assembling a battery; and then assembled into a battery.
Example 2
The embodiment provides a preparation method of a folding graphene current collector,
1) preparing a current collector X1: selecting 0.005mm aluminum wire and 100000 x 10 x 0.005mm aluminum foil, weaving into 0.02mm a and 0.02mm b net-shaped current collector by textile technology as shown in figure 7, wherein the length of the current collector is 100000mm, and the width of the current collector is 300 mm;
2) preparing a current collector X3: selecting graphene slurry with 5% of solid content, uniformly spraying the graphene slurry on X1 by using a spraying machine, wherein the non-woven part of X1 is not sprayed, drying the sprayed current collector in a drying channel to obtain a current collector X2, passing the X2 through an atomization area with 5% of conductive fiber silk solution to uniformly distribute the conductive fiber silk on the current collector X2, drying to obtain a current collector X3, and rolling X3; the length of the prepared current collector is 100000mm, the width is 300mm, and the thickness is 0.01 mm;
3) preparing current collectors Y and Z: selecting an aluminum foil with the thickness of 0.01mm, the width of 300mm and the length of 100000mm, spraying a graphite coating with the thickness of 0.0002mm on each of two sides of the aluminum foil by using a spraying technology as shown in figure 2, and drying to obtain a current collector Y; aligning the X3 with the Y up and down, and welding the non-woven part of the current collector X3 and the non-coating part of the Y by adopting a spot welding technology to obtain a current collector Z; wherein the number of X3 and Y layers is 1.
4) Preparing active material slurry: according to the positive electrode LFP: carbon black: PVDF 96: 1: and 3, preparing the anode slurry by adopting a planetary mixer.
5) Manufacturing a pole piece: coating the positive electrode slurry on the area A of the current collector Z for the first time by using an extrusion coating machine, then folding and flatly paving the area B of the current collector Z on the area A, coating the second slurry by using a second extrusion coating machine, drying by using a drying channel, coating the positive electrode material on the reverse side of the electrode piece, drying, and then rolling and slicing to obtain the positive electrode piece with the length, width and thickness of 150mm 0.2mm, which can be used for assembling the battery, as shown in figure 6.
6) Manufacturing a battery: and (3) selecting the positive pole piece obtained in the step 5), the diaphragm, the negative pole piece in the embodiment 1, the aluminum plastic film, the tab and the electrolyte to assemble the battery.
Example 3
1) Preparing a current collector X1: selecting aluminum wire with R of 0.005mm and aluminum foil with length, width and height of 100000 x 10 x 0.005mm, and weaving into mesh-structured current collector with a of 0.02mm and b of 0.02mm by textile technology as shown in figure 1. The collector has a length of 100000mm and a width of 300 mm.
2) Preparing a current collector X3: selecting graphene slurry with 5% of solid content, uniformly spraying the graphene slurry on X1 by using a spraying machine, wherein the non-woven part of X1 is not sprayed, drying the sprayed current collector in a drying channel to obtain a current collector X2, passing the X2 through an atomization area with 5% of conductive fiber silk solution to uniformly distribute the conductive fiber silk on the current collector X2, drying to obtain a current collector X3, and rolling X3; the prepared current collector has the length of 100000mm, the width of 300mm and the thickness of 0.01 mm.
3) Preparing current collectors Y and Z: selecting an aluminum foil with the thickness of 0.01mm, the width of 300mm and the length of 100000mm, spraying a graphite coating with the thickness of 0.0002mm on each of two sides of the aluminum foil by using a spraying technology as shown in figure 2, and drying to obtain a current collector Y; and aligning the X3 and the Y up and down, and welding the non-woven part of the current collector X3 and the non-coating part of the Y by adopting a spot welding technology to obtain a current collector Z. Wherein X3 is 2 layers and Y is 1 layer. As shown in fig. 3 and 4.
4) Preparing active material slurry: according to the positive electrode LFP: carbon black: PVDF 98.5: 0.5: 1, preparing the anode slurry by adopting a planetary mixer.
5) Manufacturing a pole piece: coating the positive electrode slurry on an area A of a current collector Z for the first time by using an extrusion spraying machine, then folding and flatly laying one side B of the Z on the area A, coating the second time slurry by using a second extrusion spraying machine, then folding and flatly laying the other side B on the area A, coating the third time slurry by using a third extrusion spraying machine, drying by using a drying tunnel, performing the same operation on the reverse side of the pole piece, and then rolling and slicing to obtain the positive electrode piece with the length, width and thickness of 150mm 0.2mm, wherein the thickness of the positive electrode piece can be assembled into a battery, and is shown in figure 6.
6) Manufacturing a battery: and (3) selecting a positive pole piece, a diaphragm, the negative pole piece in the embodiment 1, an aluminum-plastic film, a tab and electrolyte to assemble the battery.
Example 4
1) Preparing a current collector X1: selecting aluminum wire with R of 0.005mm and aluminum foil with length, width and height of 100000 x 10 x 0.005mm, and weaving into mesh-structured current collector with a of 0.02mm and b of 0.02mm by textile technology as shown in figure 7. The length of the current collector is 100000mm, and the width of the current collector is 450 mm.
2) Preparing a current collector X3: selecting graphene slurry with solid content of 5%, uniformly spraying the graphene slurry on X1 by using a spraying machine, wherein the non-woven part of X1 is not sprayed, drying the sprayed current collector by using a drying channel to obtain a current collector X3, and rolling X3; the prepared current collector has the length of 100000mm, the width of 300mm and the thickness of 0.01 mm.
3) Preparing current collectors Y and Z: selecting an aluminum foil with the thickness of 0.01mm, the width of 300mm and the length of 100000mm, spraying a graphite coating with the thickness of 0.0002mm on each of two sides of the aluminum foil by using a spraying technology as shown in figure 2, and drying to obtain a current collector Y; and aligning the X3 and the Y up and down, and welding the non-woven part of the current collector X2 and the non-coating part of the Y by adopting a spot welding technology to obtain a current collector Z. Wherein X3 is 1 layer and Y is 1 layer.
4) Preparing active material slurry: according to the positive electrode LFP: carbon black: PVDF 96: 1: and 3, preparing the anode slurry by adopting a planetary mixer.
5) Manufacturing a pole piece: coating the positive electrode slurry on an area A of a current collector Z for the first time by using an extrusion spraying machine, then folding and flatly paving one side B of the Z on the area A, coating the second time slurry by using a second extrusion spraying machine, drying the slurry by using a drying channel, then carrying out the same operation on the reverse side of the pole piece, and then rolling and slicing to obtain the positive pole piece with the length, width and thickness of 150mm 0.2mm, wherein the battery can be assembled; as shown in fig. 6.
6) Manufacturing a battery: and (3) selecting a positive pole piece, a diaphragm, the negative pole piece in the embodiment 1, an aluminum-plastic film, a tab and electrolyte to assemble the battery.
The batteries assembled in examples 1 to 4 were tested, and the results are shown in Table 1.
TABLE 1 test results of examples 1 to 4
Figure BDA0002803175990000071
Note: the amounts of foil and additives used are calculated as 100% for the examples.
As can be seen from table 1, the folded graphene current collector provided by the invention has low internal resistance, good rate capability and high specific energy.
In addition, compared with the traditional aluminum foil, the metal consumption can be reduced, and the use cost of the foil can be reduced in the embodiments 2 to 4.
Therefore, the folding graphene current collector provided by the invention can reduce internal resistance, greatly improve the multiplying power of a battery, improve the mechanical property of the current collector and reduce the use cost of foil.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention and not to limit it; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.

Claims (10)

1. The folding graphene current collector is characterized by comprising a coating current collector and a woven current collector combined with the coating current collector; the coating current collector is provided with a coating part, a non-coating part and a lug part; wherein the non-woven portion is secured to the non-coated portion.
2. The folded graphene current collector of claim 1, wherein the braided portions include a second braided portion and two first braided portions of the same area; the non-woven parts are positioned on two sides of the second woven part, and the first woven part is positioned on one side of one non-woven part, which is far away from the second woven part; or the first weaving part and the non-weaving part are symmetrically arranged at two sides of the second weaving part.
3. The folded graphene current collector of claim 2, wherein the area of the coating portion is the same as the area of the second braided portion, the area of the non-braided portion is the same as the area of the non-coating portion, and the area of the first braided portion is equal to the sum of the areas of the second braided portion and the two non-braided portions.
4. The method of preparing the folded graphene current collector of claim 1, wherein the method comprises the steps of:
1) preparing a braided current collector: selecting metal wires with the diameter of R and aluminum foils with the length, width and height of m X n X h, weaving the metal wires and the aluminum foils into a net structure with the length of a and the width of b, and marking the net structure as a current collector X1; firstly, spraying a graphene solution on the surface of X1, and drying to obtain a current collector X2; then, drying the X2 in a conductive fiber silk solution atomization area to obtain a current collector X3;
2) preparing a coating current collector, marked as Y, wherein the coating is made of graphite; welding the non-woven part of the X3 obtained in the step 1) and the non-coating part of the Y to obtain a foldable graphene current collector, and recording as Z; wherein Y is one layer, and the number of X3 layers is 1-100 layers;
3) preparing active material slurry of the lithium ion battery, coating a layer of active material on the area A of the current collector Z obtained in the step 2), folding and embedding the area B of the current collector Z into the active material, and coating a layer of active material; wherein the area B of the current collector Z is in unilateral distribution or bilateral distribution, the number is 1-100, and the number of times of coating the active substance is two times more than the number of the area B of the current collector Z.
5. The method for preparing the foldable graphene current collector as claimed in claim 4, wherein in the step 1), R is 0.005-1mm, a is 0.01-100 mm; b is 0.01-100mm, m is more than or equal to 1000mm, n is 10-100mm, and h is 0.005-1 mm.
6. The method for preparing the foldable graphene current collector as claimed in claim 4, wherein in the step 1), the conductive fiber filaments have a length of 0.001-30mm and a diameter of 0.000001-0.1 mm.
7. The preparation method of the folded graphene current collector as claimed in claim 4, wherein in the step 1), graphene slurry with a solid content of 3% -8% is sprayed on the surface of the weaving part of the X1.
8. The preparation method of the folded graphene current collector as claimed in claim 4, wherein in the step 1), the X2 passes through an atomization zone containing 3-8% of conductive fiber silk solution.
9. A lithium ion battery comprising the folded graphene current collector according to any one of claims 1 to 3 or the folded graphene current collector prepared by the preparation method according to any one of claims 4 to 8.
10. The lithium ion battery according to claim 9, wherein the preparation method of the lithium ion battery comprises: coating the positive pole slurry on a coating part A of a current collector Z for the first time by using an extrusion coating machine, then folding and flatly laying a weaving part B of the Z on the coating part A, coating the positive pole slurry for the second time by using a second extrusion coating machine, folding and flatly laying the weaving part B on the other side on the coating part A, repeating the steps for multiple times, drying the coating part A by using a drying tunnel, turning over the coating part A for the same operation, and rolling and slicing the coating part B to obtain a positive pole piece capable of assembling the battery; and assembling the positive pole piece, the diaphragm, the negative pole piece, the aluminum plastic film, the tab and the electrolyte into the battery.
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