CN114188507A - Negative pole piece, preparation method thereof and lithium ion battery - Google Patents
Negative pole piece, preparation method thereof and lithium ion battery Download PDFInfo
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- CN114188507A CN114188507A CN202111271520.2A CN202111271520A CN114188507A CN 114188507 A CN114188507 A CN 114188507A CN 202111271520 A CN202111271520 A CN 202111271520A CN 114188507 A CN114188507 A CN 114188507A
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 61
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 61
- 238000002360 preparation method Methods 0.000 title abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 91
- 229910021389 graphene Inorganic materials 0.000 claims description 73
- 239000011230 binding agent Substances 0.000 claims description 34
- 239000002033 PVDF binder Substances 0.000 claims description 30
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 30
- 238000001035 drying Methods 0.000 claims description 26
- 229910002804 graphite Inorganic materials 0.000 claims description 25
- 239000010439 graphite Substances 0.000 claims description 25
- 239000007773 negative electrode material Substances 0.000 claims description 25
- 239000011248 coating agent Substances 0.000 claims description 22
- 238000000576 coating method Methods 0.000 claims description 22
- 239000006258 conductive agent Substances 0.000 claims description 16
- 239000011267 electrode slurry Substances 0.000 claims description 14
- 239000002002 slurry Substances 0.000 claims description 14
- 239000000758 substrate Substances 0.000 claims description 13
- 239000002904 solvent Substances 0.000 claims description 10
- -1 graphite alkene Chemical class 0.000 claims description 9
- 239000013543 active substance Substances 0.000 claims description 7
- 239000011149 active material Substances 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 239000006229 carbon black Substances 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 3
- 238000005096 rolling process Methods 0.000 claims description 3
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 description 20
- 230000000052 comparative effect Effects 0.000 description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 11
- 239000011889 copper foil Substances 0.000 description 11
- 239000003792 electrolyte Substances 0.000 description 10
- 239000000843 powder Substances 0.000 description 9
- 238000001291 vacuum drying Methods 0.000 description 9
- 238000003756 stirring Methods 0.000 description 8
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 229910001290 LiPF6 Inorganic materials 0.000 description 6
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- UYXQLQUXXCIFQM-UHFFFAOYSA-N 2-hydroxy-1,3,2$l^{5}-dioxaphospholane 2-oxide Chemical compound OP1(=O)OCCO1 UYXQLQUXXCIFQM-UHFFFAOYSA-N 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000005520 cutting process Methods 0.000 description 3
- 229910003002 lithium salt Inorganic materials 0.000 description 3
- 159000000002 lithium salts Chemical class 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 238000007790 scraping Methods 0.000 description 2
- XMWRBQBLMFGWIX-UHFFFAOYSA-N C60 fullerene Chemical compound C12=C3C(C4=C56)=C7C8=C5C5=C9C%10=C6C6=C4C1=C1C4=C6C6=C%10C%10=C9C9=C%11C5=C8C5=C8C7=C3C3=C7C2=C1C1=C2C4=C6C4=C%10C6=C9C9=C%11C5=C5C8=C3C3=C7C1=C1C2=C4C6=C2C9=C5C3=C12 XMWRBQBLMFGWIX-UHFFFAOYSA-N 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910003472 fullerene Inorganic materials 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a negative pole piece and a preparation method thereof and a lithium ion battery. The negative pole piece provided by the invention can obviously improve the capacity of the negative pole piece and improve the rate capability and the cycle performance of the lithium ion battery.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a negative pole piece, a preparation method of the negative pole piece and a lithium ion battery.
Background
The lithium ion battery is a novel energy storage element with special advantages of high energy density, low self-discharge, no memory effect and the like, and in recent years, the lithium ion battery is widely applied to portable wearable energy storage elements such as mobile phones, flat plates and electric vehicles. The lithium ion battery mainly comprises three parts, namely a positive electrode, a negative electrode and electrolyte, wherein generally lithium iron phosphate is used as a positive electrode material of the lithium ion battery, and when the battery is charged, lithium ions are extracted from the positive electrode and are embedded into the negative electrode material through the electrolyte; when the battery is discharged, lithium ions are extracted from the negative electrode and inserted into the positive electrode material through the electrolyte. Generally, graphite is used as a negative electrode of a lithium ion battery, the lithium ion battery taking the graphite as the negative electrode can provide stable working voltage, the lithium ion battery taking the graphite as the negative electrode has long cycle life and high coulombic efficiency, but the theoretical capacity of the graphite is only 372mAh/g (measured under the conditions that the current density is 200mA/g and the temperature is 25 ℃), so that the electrochemical performance of the lithium ion battery is greatly limited.
In view of the above, how to improve electrochemical properties such as capacity of the negative electrode of the lithium ion battery is a technical problem to be solved in the art.
Disclosure of Invention
The invention provides a negative pole piece, a preparation method thereof and a lithium ion battery, which can obviously improve the capacity of a negative pole of the lithium ion battery, improve the rate capability and the cycle performance of the lithium ion battery and effectively overcome the defects in the prior art.
In one aspect of the invention, a negative electrode plate is provided, which includes a negative electrode current collector, a graphene layer located on the surface of the negative electrode current collector, and a negative electrode active material layer located on the surface of the graphene layer, wherein the graphene layer includes graphene, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes graphite.
According to an embodiment of the present invention, the average particle size of the graphene is 500nm to 5000 nm; and/or the number of layers of the graphene is 1-10.
According to an embodiment of the present invention, the graphene layer further includes a first binder, and the mass content of graphene in the graphene layer is 50% to 95%, and the balance is the first binder.
According to an embodiment of the present invention, the graphene layer further comprises a first binder, the first binder comprising polyvinylidene fluoride.
According to an embodiment of the invention, the graphene layer has a thickness of 5 μm to 1000 μm.
According to one embodiment of the present invention, the negative electrode active material layer further includes a conductive agent and a second binder, and the negative electrode active material layer contains 50% to 90% by mass of the negative electrode active material, 5% to 50% by mass of the conductive agent, and 5% to 50% by mass of the second binder.
According to an embodiment of the present invention, the negative electrode active material layer further includes a conductive agent and a second binder, the conductive agent including carbon black; and/or, the second binder comprises polyvinylidene fluoride.
According to one embodiment of the present invention, the thickness of the negative electrode active material layer is 5 μm to 1000 μm.
In a second aspect of the present invention, a method for preparing a negative electrode plate is provided, including: placing graphene and a binder in a first solvent to prepare a substrate slurry; coating the substrate slurry on the surface of the negative current collector, and drying to form a graphene layer; placing the negative electrode active material, the conductive agent and the binder in a second solvent to prepare negative electrode slurry; and coating the negative electrode slurry on the surface of the graphene layer, drying and rolling to form a negative electrode active substance layer, and thus obtaining the negative electrode piece.
In a third aspect of the present invention, a lithium ion battery is provided, which includes the above negative electrode plate.
The implementation of the invention has at least the following beneficial effects:
according to the negative pole piece provided by the invention, the graphene layer is added between the negative pole current collector and the negative pole active material, so that the capacity and other properties of the negative pole piece can be obviously improved, and further the capacity, the cyclicity and other properties of the lithium ion battery are improved.
The preparation method of the negative pole piece can prepare the negative pole piece with the performance, has the advantages of simple process, convenience in operation and the like, and is beneficial to industrial application.
Drawings
Fig. 1 (a) is a photograph of the copper foil of example 1, fig. 1 (b) is a photograph of the copper foil of example 1 after the graphene layer is coated thereon, and fig. 1 (c) is a negative electrode sheet of example 1;
FIG. 2 is a graph of rate performance of the lithium ion battery in example 1 of the present invention during charge and discharge tests at currents of 200mA/g, 400mA/g, 600mA/g, 800mA/g, and 1000mA/g, respectively;
FIG. 3 is a charging/discharging curve diagram of the lithium ion battery in example 2 of the present invention under the current condition of 800 mA/g;
FIG. 4 is a charge/discharge curve diagram of the lithium ion battery in example 2 of the present invention under the current condition of 1000 mA/g;
FIG. 5 is a graph showing the charge and discharge curves of the lithium ion battery of example 3 of the present invention and the lithium ion battery of comparative example 1 at a current of 400 mA/g;
FIG. 6 is a graph showing charge and discharge curves of the lithium ion battery in example 3 of the present invention and the lithium ion battery in comparative example 1 at a current of 600 mA/g;
FIG. 7 is a graph showing rate performance of the lithium ion battery of example 4 of the present invention and the lithium ion battery of comparative example 1 under the current conditions of 200mA/g, 400mA/g, 600mA/g, 800mA/g, and 1000mA/g during the charge/discharge test;
fig. 8 is a graph of cycle performance of the lithium ion battery of example 5 of the present invention when performing a charge/discharge test at a current of 400 mA/g.
Detailed Description
The following detailed description is merely illustrative of the principles and features of the present invention, and the examples are intended to be illustrative of the invention and not limiting of the scope of the invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the protection scope of the present invention.
The invention provides a negative pole piece which comprises a negative pole current collector, a graphene layer positioned on the surface of the negative pole current collector and a negative pole active substance layer positioned on the surface of the graphene layer, wherein the graphene layer contains graphene, the negative pole active substance layer contains a negative pole active substance, and the negative pole active substance contains graphite.
The graphene is sp2Novel carbon materials built up from hybridly bound carbon atoms having twoThe dimensional structure is a basic structural unit constituting a graphite sheet, a carbon nanotube, and fullerene. The graphene has excellent electrochemical properties and physical properties, has the advantages of strong conductivity, high hardness, good ductility and the like, and can be applied to a current collector in a lithium ion battery to enhance the conductivity of a negative electrode of the lithium ion battery.
The negative electrode current collector is a structure or a part for collecting current, and includes a metal current collector, such as a metal foil, and particularly, a copper foil. The specific surface area of graphite alkene is great, and is flexible material, and the surface of attaching to the negative pole mass flow body that can be better, in the graphite alkene layer that the negative pole mass flow body surface formed, graphite alkene evenly distributed in the graphite alkene layer, intercrossing forms the conducting network between the graphite alkene, can show the electric conductivity that improves the negative pole piece, improves ion transmission speed, can furthest collect the electric current to reduce the contact resistance between the negative pole mass flow body and the negative pole active material.
The present invention may employ graphite which is conventional in the art, commercially available or self-made, for example, conventional commercial graphite, etc., without particular limitation.
In some embodiments, the graphene has an average particle size of 500nm to 5000nm, such as 500nm, 1000nm, 2000nm, 3000nm, 4000nm, 5000nm, or any two thereof, and the number of graphene layers is 1 to 10, such as 1, 2, 4, 5, 8, 10.
In some embodiments, the graphene layer further comprises a first binder, the mass content of graphene in the graphene layer is 50% to 95%, such as in the range of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any two thereof, with the balance being the first binder, e.g., when the mass content of graphene in the graphene layer is 95%, the mass content of the first binder is 5%.
In some embodiments, the graphene layer further includes a first binder, and the first binder includes polyvinylidene fluoride (PVDF), but is not limited thereto, and other conventional binders in the art may also be used in the present invention, and in contrast, PVDF is more favorable for being matched with components such as graphene, etc., so as to improve the electrochemical performance of the negative electrode plate.
In some embodiments, the graphene layer has a thickness of 5-1000 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 100 μm, 500 μm, 1000 μm, or a range consisting of any two thereof.
In some embodiments, the negative electrode active material layer further includes a conductive agent and a second binder, and the negative electrode active material layer has a mass content of 50% to 90%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or a range of any two thereof, and the conductive agent has a mass content of 5% to 50%, for example, 5%, 10%, 20%, 30%, 40%, 50%, or a range of any two thereof. The second binder is present in an amount of 5% to 50% by mass, for example 5%, 10%, 20%, 30%, 40%, 50% or any two thereof.
In some embodiments, the negative electrode active material layer further comprises a conductive agent and a second binder, wherein the conductive agent may include carbon black, and the second binder includes polyvinylidene fluoride (PVDF), and the second binder can increase the adhesive strength between the negative electrode active material layer and the graphene layer, thereby further ensuring the function of the negative electrode plate.
In some embodiments, the thickness of the negative electrode active material layer is 5 μm to 1000 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 100 μm, 500 μm, 1000 μm, or a range consisting of any two thereof.
The preparation method of the negative pole piece comprises the following steps: placing graphene and a binder in a first solvent to prepare a substrate slurry; coating the substrate slurry on the surface of the negative current collector, and drying to form a graphene layer; placing the negative electrode active material, the conductive agent and the binder in a second solvent to prepare negative electrode slurry; and coating the negative electrode slurry on the surface of the graphene layer, drying and rolling to form a negative electrode active substance layer, and thus obtaining the negative electrode piece.
The first solvent may include nitrogen methyl pyrrolidone, and the second solvent may include nitrogen methyl pyrrolidone, but is not limited thereto, and other conventional solvents in the art may be used in the present invention.
In the specific implementation process of the invention, the substrate slurry is uniformly coated on the surface of the negative current collector by using a coating device in the field such as a coating machine or a coater, and then dried (for example, dried in an oven) at 80-120 ℃, so as to form the graphene layer on the surface of the negative current collector.
In specific implementation, after the negative electrode active material, the conductive agent and the binder are placed in the second solvent, a magnetic stirrer can be used for stirring to uniformly mix the system to prepare the negative electrode slurry, and the stirring time can be generally 4-8 hours, for example 6 hours.
The negative electrode slurry can be coated on the surface of a negative electrode current collector by using a coating machine and other conventional coating devices in the field, then dried at 80-120 ℃ (such as drying in an oven), then rolled and cut into sheets meeting the shape and size requirements by using a tablet press, and further dried at 50-90 ℃ (such as drying in a vacuum oven), for example, 70 ℃, so that the slurry coated on the surface of the current collector forms a negative electrode active material layer to prepare a negative electrode sheet.
The invention provides a lithium ion battery which comprises the negative pole piece. The lithium ion battery may be, for example, a button cell battery, but is not limited thereto, and may be manufactured according to a conventional method in the art.
The lithium ion battery also comprises a positive plate and a diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate and used for separating the positive plate from the negative plate. The present invention may employ positive electrode sheets and separators that are conventional in the art, such as lithium sheets, and are commercially or self-made.
In addition, the lithium ion battery further contains an electrolyte, and the electrolyte may contain an organic solvent and a lithium salt, wherein the organic solvent may include ethylene phosphate and/or dimethyl carbonate, and the lithium salt may include lithium hexafluorophosphate (LiPF)6) The concentration of the lithium salt in the electrolyte is, for example, in the range of 0.8mol/L to 1.5mol/L, for example, 0.8mol/L, 1mol/L, 1.5mol/L, or any two of them, but the composition of the electrolyte is not limited thereto.
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.
Example 1
1. Preparation of negative pole piece
(1) Adding graphene powder and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing the graphene powder and the PVDF by using a magnetic stirrer to obtain a substrate slurry, wherein the mass ratio of the graphene powder to the PVDF is 95: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(2) coating the substrate slurry on the surface of a copper foil in a blade mode by using a coating machine, drying in a drying oven at 100 ℃, and forming a graphene layer on the surface of the copper foil, wherein the thickness of the graphene layer is controlled to be 15 microns;
(3) adding commercial graphite, conductive carbon black and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing by using a magnetic stirrer to obtain negative electrode slurry, wherein the mass ratio of the commercial graphite to the conductive carbon black to the PVDF is 90: 5: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(4) uniformly coating the negative electrode slurry on a graphene layer by using a coating machine, drying in a drying oven at 100 ℃, cutting into electrode slices with the diameter of 13mm by using a tablet press after drying, and drying the electrode slices in a vacuum drying oven to obtain a negative electrode slice, wherein the temperature of the vacuum drying oven is 70 ℃, and the vacuum drying time is 4 hours.
2. Lithium ion battery
Adopting a lithium plate as a positive plate, and forming the positive plate, a celgard2400 diaphragm and a negative plate into a buckle type in a glove box filled with argon gasThe battery, the electrolyte used by the button battery is composed of ethylene phosphate, dimethyl carbonate and LiPF6Composition of, wherein LiPF6The concentration of (2) is 1 mol/L.
Example 2
1. Preparation of negative pole piece
(1) Adding graphene powder and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing the graphene powder and the PVDF by using a magnetic stirrer to obtain a substrate slurry, wherein the mass ratio of the graphene powder to the PVDF is 95: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(2) coating the substrate slurry on a copper foil by a coating machine in a scraping way, and drying in a drying oven at 100 ℃ to realize the formation of the graphene layer on the surface of the copper foil, wherein the thickness of the graphene layer is controlled to be 25 mu m;
(3) adding commercial graphite, conductive carbon black and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing by using a magnetic stirrer to obtain negative electrode slurry, wherein the mass ratio of the commercial graphite to the conductive carbon black to the PVDF is 90: 5: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(4) uniformly coating the negative electrode slurry on a graphene layer by using a coating machine, drying in a drying oven at 100 ℃, cutting into electrode slices with the diameter of 13mm by using a tablet press after drying, and drying the electrode slices in a vacuum drying oven to obtain a negative electrode slice, wherein the temperature of the vacuum drying oven is 70 ℃, and the vacuum drying time is 4 hours.
2. Lithium ion battery
A lithium plate is adopted as a positive plate, the positive plate, a celgard2400 diaphragm and a negative plate are combined into a button cell in a glove box filled with argon, and electrolyte used by the button cell is composed of ethylene phosphate, dimethyl carbonate and LiPF6Composition of, wherein LiPF6The concentration of (2) is 1 mol/L.
Example 3
1. Preparation of negative pole piece
(1) Adding graphene powder and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing the graphene powder and the PVDF by using a magnetic stirrer to obtain a substrate slurry, wherein the mass ratio of the graphene powder to the PVDF is 95: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(2) coating the substrate slurry on a copper foil by a coating machine in a scraping way, and drying in a drying oven at 100 ℃ to realize the formation of the graphene layer on the surface of the copper foil, wherein the thickness of the graphene layer is controlled to be 20 mu m;
(3) adding commercial graphite, conductive carbon black and PVDF into a nitrogen methyl pyrrolidone solution, and uniformly mixing by using a magnetic stirrer to obtain negative electrode slurry, wherein the mass ratio of the commercial graphite to the conductive carbon black to the PVDF is 90: 5: 5, taking the total weight of the nitrogen methyl pyrrolidone solution as 100 percent, wherein the concentration of the polyvinylidene fluoride in the nitrogen methyl pyrrolidone solution is 7 percent by weight, and the stirring time is 6 hours;
(4) uniformly coating the negative electrode slurry on a graphene layer by using a coating machine, drying in a drying oven at 100 ℃, cutting into electrode slices with the diameter of 13mm by using a tablet press after drying, and drying the electrode slices in a vacuum drying oven to obtain a negative electrode slice, wherein the temperature of the vacuum drying oven is 70 ℃, and the vacuum drying time is 4 hours.
2. Lithium ion battery
A lithium plate is adopted as a positive plate, the positive plate, a celgard2400 diaphragm and a negative plate are combined into a button cell in a glove box filled with argon, and electrolyte used by the button cell is composed of ethylene phosphate, dimethyl carbonate and LiPF6Composition of, wherein LiPF6The concentration of (2) is 1 mol/L.
Comparative example 1
Compared with example 1, the negative electrode sheet of comparative example 1 has no base paste, and other conditions are unchanged.
The structures and properties of the lithium ion batteries of the examples and comparative examples were characterized by the following test methods:
1. rate capability test
The test instrument is a Xinwei charge-discharge tester;
the test conditions were: in an environment at room temperature of 25 ℃, charge and discharge tests were carried out under the conditions of current densities of 200mA/g, 400mA/g, 600mA/g, 800mA/g and 1000mA/g, and the change of the capacity with the number of cycles was measured.
2. Cycle life test
The test instrument is a Xinwei charge-discharge tester;
the test conditions were: the charge and discharge test was carried out at a current of 400mA/g in an environment of 25 ℃ at room temperature, and the change in the capacity of the negative electrode piece with the increase in the number of cycles was measured.
Fig. 1 (a) is a photograph of the copper foil of example 1, fig. 1 (b) is a photograph of the copper foil of example 1 coated with a graphene layer having a thickness of 15 μm, and fig. 1 (c) is a negative electrode sheet of example 1.
The rate performance curve of the lithium ion battery in example 1 is shown in FIG. 2 when the lithium ion battery is subjected to charge and discharge tests at current densities of 200mA/g, 400mA/g, 600mA/g, 800mA/g and 1000mA/g, respectively. As can be seen from fig. 2, the negative electrode capacity of the lithium ion battery gradually decreases as the current density of charging and discharging increases, and the capacity of the negative electrode tab is the largest when the charging and discharging test is performed at a current density of 200 mA/g.
The charge and discharge curves of the lithium ion battery in example 2 at a current of 800mA/g are shown in FIG. 3. As can be seen from FIG. 3, the capacity of the negative electrode sheet in example 2 was 88mAh/g when charged and discharged at a current density of 800 mA/g.
The charge and discharge curves of the lithium ion battery in example 2 at a current of 1000mA/g are shown in FIG. 4.
The charge and discharge curves at a current of 400mA/g of the lithium ion battery in example 3 and the lithium ion battery in comparative example 1 are shown in fig. 5. As can be seen from FIG. 5, when the negative electrode sheet in example 3 was charged and discharged at a current density of 400mA/g, the capacity of the negative electrode sheet was 200mAh/g, which is much higher than that of the negative electrode sheet without the graphene layer in comparative example 1 (130 mAh/g).
The charge and discharge curves at a current of 600mA/g of the lithium ion battery in example 3 and the lithium ion battery in comparative example 1 are shown in fig. 6. As can be seen from fig. 6, when charging and discharging are performed at a current density of 600mA/g, the capacity of the negative electrode sheet in example 3 is 128mAh/g, which is much higher than the capacity of the negative electrode sheet without the graphene layer in comparative example 1 at the current density (59mAh/g), and the negative electrode sheet in example 3 has a broader platform of 0.5V or less.
The graphs of the rate performance of the lithium ion battery in example 4 and the lithium ion battery in comparative example 1 when the charge and discharge tests were performed at current densities of 200mA/g, 400mA/g, 600mA/g, 800mA/g, and 1000mA/g are shown in FIG. 7. As can be seen from FIG. 7, the maximum capacity of the negative electrode tab in example 4 at a current density of 200mA/g is 605mAh/g, which is much higher than the capacity of the negative electrode tab without the graphene layer in comparative example 1 at the current density (236 mAh/g).
When the lithium ion battery in example 5 is subjected to the charge and discharge test at the current density of 400mA/g, the cycle performance curve of the lithium ion battery is shown in fig. 8, and it can be seen from fig. 8 that the reversible capacity of the lithium ion battery in example 5 can still reach 200mAh/g after the lithium ion battery is subjected to the charge and discharge cycle for 100 times at the current density of 400 mA/g.
In summary, the negative electrode plate, the preparation method thereof and the lithium ion battery provided by the invention have the advantages that the negative electrode plate comprises the graphene layers, the graphene in the graphene layers is uniformly distributed, and the graphene layers are mutually crossed to form a conductive network, so that the conductivity of the negative electrode plate can be obviously improved, the ion transmission speed is improved, and the current can be collected to the maximum extent, so that the maximum capacity of the negative electrode plate is improved, and the rate capability and the cycle performance of the lithium ion battery can be improved by applying the negative electrode plate to the lithium ion battery.
In addition, the preparation method of the negative pole piece provided by the invention is simple in process, convenient to operate and suitable for industrial application.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The utility model provides a negative pole piece, its characterized in that includes the negative pole current collector, is located the graphite alkene layer on negative pole current collector surface, be located the negative pole active material layer on graphite alkene layer surface, graphite alkene layer contains graphite, the negative pole active material layer contains negative pole active material, the negative pole active material includes graphite.
2. The negative electrode plate of claim 1, wherein the average particle size of the graphene is 500nm to 5000 nm; and/or the number of layers of the graphene is 1-10.
3. The negative electrode plate as claimed in claim 1, wherein the graphene layer further comprises a first binder, the graphene in the graphene layer has a mass content of 50% to 95%, and the balance is the first binder.
4. The negative electrode tab of claim 1 or 3, wherein the graphene layer further comprises a first binder, the first binder comprising polyvinylidene fluoride.
5. The negative electrode tab of claim 1, wherein the graphene layer has a thickness of 5 μm to 1000 μm.
6. The negative electrode plate of claim 1, wherein the negative electrode active material layer further comprises a conductive agent and a second binder, and the negative electrode active material layer contains the negative electrode active material in an amount of 50 to 90% by mass, the conductive agent in an amount of 5 to 50% by mass, and the second binder in an amount of 5 to 50% by mass.
7. The negative electrode sheet according to claim 1 or 5, wherein the negative electrode active material layer further contains a conductive agent and a second binder, the conductive agent comprising carbon black; and/or the second binder comprises polyvinylidene fluoride.
8. The negative electrode tab according to claim 1, wherein the thickness of the negative electrode active material layer is 5 μm to 1000 μm.
9. The method for preparing the negative electrode plate of any one of claims 1 to 8, comprising:
placing graphene and a binder in a first solvent to prepare a substrate slurry;
coating the substrate slurry on the surface of a negative current collector, and drying to form a graphene layer;
placing the negative electrode active material, a conductive agent and a binder in a second solvent to prepare negative electrode slurry;
and coating the negative electrode slurry on the surface of the graphene layer, and drying and rolling to form a negative electrode active substance layer to obtain the negative electrode piece.
10. A lithium ion battery comprising the negative electrode sheet according to any one of claims 1 to 8.
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