CN112599719A - Negative plate, preparation method of negative plate and battery - Google Patents
Negative plate, preparation method of negative plate and battery Download PDFInfo
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- CN112599719A CN112599719A CN202011470980.3A CN202011470980A CN112599719A CN 112599719 A CN112599719 A CN 112599719A CN 202011470980 A CN202011470980 A CN 202011470980A CN 112599719 A CN112599719 A CN 112599719A
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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
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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
- 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
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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
- H01M4/139—Processes of manufacture
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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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
Abstract
The invention provides a negative plate, a preparation method of the negative plate and a battery, wherein the negative plate comprises the following components: the current collector comprises a current collector body, wherein a first coating area is arranged on the first surface of the current collector body, and a second coating area is arranged on the second surface of the current collector body; the coating comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on one side, far away from the current collector, of the first coating. In the invention, the first coating comprises a first active substance with high energy density, and a second coating is arranged on the side of the first coating far away from the current collector, wherein the second coating comprises a conductive agent with high conductivity. The coating with high energy density and the coating with high conductivity are arranged on the current collector, so that the energy density of the battery is improved on the premise of not losing the quick charging performance of the battery.
Description
Technical Field
The invention relates to the technical field of battery materials, in particular to a negative plate, a preparation method of the negative plate and a battery.
Background
With the development of battery technology, the position of polymer lithium ion batteries is becoming more and more important, and people are no longer seeking high energy density for lithium ion batteries singly, and the requirement for the quick charging performance of batteries is becoming higher and higher.
In the prior art, in order to ensure that the energy density of the battery is high, high-compaction graphite is mostly adopted as a negative electrode active material, and when the battery using the material is charged at a high rate, the phenomenon of lithium precipitation of a negative electrode sheet often occurs based on the characteristics of the high-compaction graphite. In this case, the lithium ion battery at present cannot be well compatible with both high energy density and fast charging.
Disclosure of Invention
The embodiment of the invention aims to provide a negative plate, a preparation method of the negative plate and a battery, which aim to improve the energy density of the battery on the premise of not losing the quick charging performance of the battery.
In order to achieve the above object, an embodiment of the present invention provides a negative electrode sheet, including: the current collector comprises a current collector body, a first coating area is arranged on the first surface of the current collector body, and a second coating area is arranged on the second surface of the current collector body;
the coating comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on one side, far away from the current collector, of the first coating;
the first coating comprises a first active substance for improving the energy density of the negative plate, and the second coating comprises a first conductive agent for improving the conductivity of the negative plate.
Optionally, the first coating includes a second conductive agent, the first conductive agent and the second conductive agent are both tubular structures, and a first tube wall thickness of the first conductive agent is greater than or equal to a second tube wall thickness of the second conductive agent.
Optionally, the pipe wall value is smaller than a first preset value and larger than a second preset value, and the first preset value is larger than the second preset value;
the pipe wall value is the product of the first pipe wall thickness and the thickness of a first target coating, divided by the product of the second pipe wall thickness and the thickness of a second target coating;
wherein the first target coating is the thicker of the first and second coatings and the second target coating is the thinner of the first and second coatings.
Optionally, the ratio of the thickness of the first coating layer to the thickness of the second coating layer is between 1:9 and 9: 1.
Optionally, the first coating includes a first active material, a second conductive agent and a binder, the first active material includes first graphite, the second conductive agent includes at least one of carbon black, carbon nanotubes and graphene, and the binder includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber compounds and polyacrylate compounds.
Optionally, the first conductive agent comprises graphyne, and the content of the graphyne in the first conductive agent is not more than 40%.
Optionally, the second coating includes a second active material, a first conductive agent, and a binder, the second active material includes second graphite, the first conductive agent includes graphdine and at least one of carbon black, carbon nanotubes, and graphene, and the binder includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber-based compounds, and polyacrylate-based compounds.
Optionally, the second coating layer has a lithium ion deintercalation rate greater than that of the first coating layer.
The embodiment of the invention also provides a preparation method of the negative plate, which comprises the following steps:
providing a current collector, wherein a first surface of the current collector is provided with a first coating area, and a second surface of the current collector is provided with a second coating area;
providing a coating on the surface of the current collector, wherein the coating comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on the side, away from the current collector, of the first coating;
the first coating comprises a first active substance for improving the energy density of the negative plate, and the second coating comprises a first conductive agent for improving the conductivity of the negative plate.
The embodiment of the invention also provides a battery, which comprises the negative plate.
One of the above technical solutions has the following advantages or beneficial effects:
in the embodiment of the invention, a first coating is arranged in a first coating area on the first surface and a second coating area on the second surface of the current collector, wherein the first coating comprises a first active material with high energy density, so that the energy density of the negative plate is improved; and a second coating is arranged on one side of the first coating, which is far away from the current collector, wherein the second coating comprises a conductive agent with high conductivity, so that the conductivity of the negative plate is improved. The coating with high energy density and the coating with high conductivity are arranged on the current collector, so that the energy density of the battery is improved on the premise of not losing the quick charging performance of the battery.
Drawings
Fig. 1 is a structural diagram of a negative electrode sheet according to an embodiment of the present invention;
fig. 2 is a flowchart of a method for preparing a negative electrode sheet according to an embodiment of the present invention.
The reference numbers illustrate:
a current collector 10; a first coating layer 20; a second coating 30.
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 some, not all, 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.
Referring to fig. 1, fig. 1 is a structural diagram of a negative electrode sheet according to an embodiment of the present invention. The negative electrode sheet in this embodiment includes: the current collector 10 comprises a current collector 10, wherein a first coating area is arranged on a first surface of the current collector 10, and a second coating area is arranged on a second surface of the current collector 10; coating layers, wherein the coating layers comprise a first coating layer 20 formed by a first coating material and a second coating layer 30 formed by a second coating material, the first coating layer 20 is arranged in a first coating area and a second coating area of the current collector 10, and the second coating layer 30 is arranged on one side of the first coating layer 20 away from the current collector 10; the first coating comprises a first active substance for improving the energy density of the negative plate, and the second coating comprises a first conductive agent for improving the conductivity of the negative plate.
In this embodiment, the current collector 10 of the negative electrode plate may be a copper foil, an aluminum foil, or a foil made of other materials, which is not specifically limited in this embodiment, and the current collector 10 is used for collecting currents generated by the battery active materials so as to form a larger current for outputting to the outside.
A first coating region is provided on a first surface of the current collector 10, a second coating region is provided on a second surface of the current collector 10, and a first coating layer 20 is provided on the first coating region and the second coating region. As shown in fig. 1, the first coated area is larger than the second coated area, and the coated area of the first coating 20 on the first surface of the current collector 10 is larger than the coated area of the first coating 20 on the second surface of the current collector 10. It is understood that in some embodiments, the first coated area may be smaller than the second coated area, and the coated area of first coating 20 on the first surface of current collector 10 is smaller than the coated area of first coating 20 on the second surface of current collector 10. In other embodiments, the first coated region may be the same as the second coated region, and the coated area of the first coating 20 on the first surface of the current collector 10 is equal to the coated area of the first coating 20 on the second surface of the current collector 10.
The first coating layer 20 is composed of a first coating material, and in an alternative embodiment, the first coating material may be applied to the first and second coating regions of the current collector 10 through a coating process.
The first coating is composed of a first active material, a second conductive agent and a binder, the first active material is an active material with high energy density, and the first coating 20 composed of the first coating has high energy density, so that the energy density of the negative plate is improved.
A second coating 30 is provided on the side of the first coating 20 remote from the current collector 10. It should be noted that, as can be seen from the above, the first coating layer 20 is disposed on both the first surface and the second surface of the current collector 10, in this case, the second coating layer 30 needs to be disposed on one side of the first coating layer 20 on the first surface of the current collector 10 and one side of the second coating layer 30 on the second surface of the current collector 10, and the coating area of the second coating layer 30 is the same as that of the first coating layer 20.
The second coating layer 30 is composed of the second dope, and in an alternative embodiment, the first coating layer 20 and the second coating layer 30 may be formed by simultaneously spraying 2 kinds of dopes, i.e., the first dope and the second dope, through a coating process using the same coating die. Alternatively, the first coating material may be applied to the surface of the current collector 10 to form the first coating layer 20, and then the second coating material may be applied to the surface of the first coating layer 20 to form the second coating layer 30, using a coating die or other coating tool.
In the embodiment of the invention, the first coating 20 is provided on the first coating region of the first surface and the second coating region of the second surface of the current collector 10, wherein the first coating 20 includes a first active material with high energy density, so as to increase the energy density of the negative electrode sheet; and a second coating 30 is arranged on the side of the first coating 20 away from the current collector 10, wherein the second coating 30 comprises a conductive agent with high conductivity, so that the conductivity of the negative plate is improved. By providing a high energy density coating and a high conductivity coating on the current collector 10, the energy density of the battery is increased without losing the quick charging performance of the battery.
As described above, the first dope includes the second conductive agent, and the second dope includes the first conductive agent.
Optionally, the first conductive agent comprises graphyne, and the content of the graphyne in the first conductive agent is not more than 40%.
In an optional embodiment, the first conductive agent is a graphite alkyne with high conductivity, and the graphite alkyne is a very ideal lithium storage material, and has a structure favorable for diffusion and transmission of lithium ions and a good rate capability.
It should be noted that, when only the graphdine is used as a single conductive agent, the whole conductive performance of the graphdine cannot be exerted, and the graphdine is generally used in combination with a conductive carbon tube, or the graphdine is used in combination with carbon black; furthermore, the content of the graphite alkyne in the conductive agent is controlled so as to fully exert the conductive performance of the graphite alkyne. That is, in an alternative embodiment, the first conductive agent includes graphyne and conductive carbon tubes, and the content of the graphyne does not exceed 40%. In another alternative embodiment, the first conductive agent comprises graphyne and carbon black, and the content of graphyne does not exceed 40%.
Alternatively, the second coating layer 30 has a lithium ion deintercalation rate greater than that of the first coating layer 20.
As described above, since the conductivity of the first conductive agent is higher than that of the second conductive agent, the kinetic performance of the second coating layer 30 composed of the first conductive agent is higher than that of the first coating layer 20 composed of the second conductive agent, and on this premise, the second coating layer 30 supports a higher charge current, so that the negative electrode sheet including the second coating layer 30 supports a quick charge function.
The kinetic performance is the deintercalation rate of lithium ions, and the higher the deintercalation rate, the better the kinetic performance.
Illustratively, the deintercalation rate of lithium ions of the second coating layer 30 is greater than the deintercalation rate of lithium ions of the first coating layer 20.
Illustratively, the supportable charging current of the second coating 30 is greater than the supportable charging current of the first coating 20.
Illustratively, the second coating layer 30 has a lithium ion acceptance rate that is greater than the lithium ion acceptance rate of the first coating layer 20.
Optionally, the first coating includes a second conductive agent, and in a case where both the first conductive agent and the second conductive agent are tubular conductive agents, a first wall thickness of the first conductive agent is greater than or equal to a second wall thickness of the second conductive agent.
In this embodiment, there may be a case where the first conductive agent and the second conductive agent are both tubular conductive agents, and illustratively, the first conductive agent includes graphdine and the second conductive agent includes carbon nanotubes, and it is understood that in some embodiments, the first conductive agent and the second conductive agent may also include other tubular conductive agents. In this case, in order to maximize the conductivity of the conductive agent, the wall thickness of the conductive agent needs to be limited.
In an alternative embodiment, the wall tube thickness of the graphdine is defined to be equal to or greater than the wall thickness of the carbon nanotubes.
Optionally, the pipe wall value is smaller than a first preset value and larger than a second preset value, and the first preset value is larger than the second preset value; the pipe wall value is the product of the first pipe wall thickness and the thickness of a first target coating, divided by the product of the second pipe wall thickness and the thickness of a second target coating; wherein the first target coating is the thicker of the first coating 20 and the second coating 30 and the second target coating is the thinner of the first coating 20 and the second coating 30.
In another alternative embodiment, the value of the pipe wall is calculated by the following formula:
wherein a is the wall tube thickness of the graphdiyne, b is the tube wall thickness of the carbon nano tube, and the calculation unit of the wall tube thickness of the graphdiyne and the tube wall thickness of the carbon nano tube is nano; c is the pipe wall value, dmax is the thickness of the first target coating, which is the thicker of the first coating 20 and the second coating 30, dmin is the thickness of the second target coating, which is the thinner of the first coating 20 and the second coating 30; the unit of calculation of the thickness of the first target coating and the thickness of the second target coating is micrometers.
The value range of the pipe wall value is limited to be smaller than a first preset value and larger than a second preset value, wherein the first preset value can be 0.321, and the second preset value can be 0.76. It should be understood that in some embodiments, the first preset value and the second preset value may also be set by a user.
Under the condition that the first conductive agent and the second conductive agent are both tubular conductive agents, the thickness of the wall tube of the first conductive agent and the thickness of the wall tube of the second conductive agent are limited through the two embodiments, so that the first conductive agent and the second conductive agent completely participate in electrochemical reaction, and the conductivity of the conductive agents is fully exerted.
Optionally, the ratio of the thickness of the first coating layer 20 to the thickness of the second coating layer 30 is between 1:9 and 9: 1.
In an embodiment of the present invention, a ratio of the thickness of the first coating layer 20 to the thickness of the second coating layer 30 is between 1:9 and 9:1, for example, the ratio of the thickness of the first coating layer 20 to the thickness of the second coating layer 30 may be any one of 3:7, 4:6, 5:5, 6:4, and 7:3, and the embodiment is not limited in detail herein.
The following specifically describes the components of the first dope and the second dope:
optionally, the first coating includes a first active material, a second conductive agent and a binder, the first active material includes first graphite, the second conductive agent includes at least one of carbon black, carbon nanotubes and graphene, and the binder includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber compounds and polyacrylate compounds.
The first active material includes a first graphite, and the first graphite is a graphite material having no high quick charging performance, and the first graphite may also be referred to as a conventional graphite.
Optionally, the second coating includes a second active material, a first conductive agent, and a binder, the second active material includes second graphite, the first conductive agent includes graphdine and at least one of carbon black, carbon nanotubes, and graphene, and the binder includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber-based compounds, and polyacrylate-based compounds.
The second active material includes a second graphite, which is a graphite material having high quick-charging performance and may be referred to as a quick-charging type graphite. Compared with the first graphite, the particle size of the second graphite is smaller than that of the first graphite, the diffusion path of lithium ions in the second graphite is relatively short, and the dynamic performance is relatively better; or the graphitization degree of the second graphite is less than that of the first graphite; or the surface of the second graphite is covered with a layer of inorganic oxide material for improving the wettability between the second graphite and the electrolyte, so that the second graphite has high quick charging performance.
Examples 1-3 and comparative examples 1-2 were set up according to the structure of the negative electrode sheet described above.
Example 1:
adding 0.2 wt% of graphite alkyne, 0.3 wt% of conductive carbon, 1.3 wt% of styrene butadiene rubber and 1.3 wt% of carboxymethyl cellulose into 96.9 wt% of quick-filling graphite, and then preparing the negative electrode slurry A by using water for regulation.
0.5 wt% of conductive carbon, 1.3 wt% of styrene-butadiene rubber and 1.3 wt% of carboxymethyl cellulose are added into 96.9 wt% of conventional graphite, and then water is used for adjustment to prepare negative electrode slurry B.
Coating the negative electrode slurry B on a negative electrode current collector 10 through double-layer coating equipment to form a first coating 20, coating the negative electrode slurry A on the negative electrode slurry B to form a second coating 30, drying, rolling, slitting and preparing a sheet to obtain the negative electrode sheet, wherein the ratio of the first coating 20 to the second coating 30 is 3: 7.
Mixing the positive active material lithium cobaltate, the conductive carbon serving as the conductive agent and the PVDF serving as the binder according to the mass ratio of 97.8:1.1:1.1, adding N-methyl pyrrolidone, stirring and dispersing to prepare positive slurry with appropriate solid content. And coating the positive electrode slurry on a positive electrode current collector 10, drying, rolling, slitting and tabletting to obtain the positive electrode plate.
And winding the negative plate prepared in the first step, the positive plate prepared in the second step and a diaphragm together to prepare a winding core, packaging the winding core by using an aluminum plastic film to prepare a battery core, then performing the procedures of liquid injection, aging, formation, secondary packaging and the like, and finally testing the electrochemical performance of the battery.
Example 2:
the other example was the same as example 1 except that the composition of the negative electrode slurry a was different, and in example 2, 0.6 wt% of conductive carbon and 0.4 wt% of graphite alkyne, 1.3 wt% of styrene-butadiene rubber, and 1.3 wt% of carboxymethyl cellulose were added to 96.4 wt% of quick-charging graphite, and then, the mixture was adjusted with water to prepare negative electrode slurry a.
Example 3:
the other example was the same as example 1 except that the composition of negative electrode slurry B was different, and in example 3, 0.2 wt% of graphdine, 0.3 wt% of conductive carbon, 1.3 wt% of styrene-butadiene rubber, and 1.3 wt% of carboxymethyl cellulose were added to 96.9 wt% of conventional graphite, and then adjusted with water to prepare negative electrode slurry B.
Comparative example 1:
otherwise, the same as example 1, except that only one layer of the negative electrode slurry a was coated on the negative electrode current collector 10.
Comparative example 2:
the other example was the same as example 1 except that the composition of the negative electrode slurry A was different, and in comparative example 2, 0.25 wt% of graphdine, 0.3 wt% of conductive carbon, 1.3 wt% of styrene-butadiene rubber, and 1.3 wt% of carboxymethyl cellulose were added to 96.85 wt% of quick-charging graphite, and then the mixture was adjusted with water to prepare negative electrode slurry A.
Wherein, the thickness of the coating layer of the negative electrode sheet and the thickness of the conductive agent of each coating layer in each of the above examples and comparative examples satisfy the following table one.
Table one:
the batteries prepared in the above examples and comparative examples were subjected to cycle performance test and energy density test, the procedures of which are as follows, and the test results are shown in table 2.
Table two:
wherein, the cycle performance at 25 ℃ in the second table refers to:
after being placed for 2 hours at the ambient temperature of 25 +/-2 ℃, the battery cell is subjected to step charging: and carrying out cycle performance test by taking the constant current charging to 4.25V at a rate of 2C, the constant voltage charging to 1.5C at a voltage of 4.25V, the constant current charging to 4.45V at a rate of 1.5C, the constant voltage charging to 0.025C at a voltage of 4.45V, standing for 5 minutes, then carrying out 0.7C discharging, cutting off the voltage to 3.0V, and standing for 5 minutes.
The cycle performance at 45 ℃ in Table II means:
after being placed for 2 hours at the ambient temperature of 45 +/-2 ℃, the battery cell is subjected to step charging: and carrying out cycle performance test by taking the constant current charging to 4.25V at a rate of 2C, the constant voltage charging to 1.5C at a voltage of 4.25V, the constant current charging to 4.45V at a rate of 1.5C, the constant voltage charging to 0.025C at a voltage of 4.45V, standing for 5 minutes, then carrying out 0.7C discharging, cutting off the voltage to 3.0V, and standing for 5 minutes.
The energy density in table two is selected as a volume energy density, and the energy density (Wh/L) is the table capacity (Ah) x the system platform voltage (V)/the cell volume (L) at room temperature.
Comparing example 1 with examples 2-3, it can be seen that:
the negative plate provided by the application can obviously improve the cycle performance and energy density of the battery on the premise of less energy density loss.
Comparing example 1 with comparative example 1, it can be seen that:
compared with the negative plate with only the first coating 20, the negative plate with the first coating 20 and the second coating 30 provided by the application has higher energy density.
Comparing example 1 with comparative example 2, it can be seen that:
in the case where the content of the graphyne in the first conductive agent exceeds 40%, the higher the content of the graphyne, resulting in a great decrease in both cycle performance and energy density of the battery.
The embodiment of the present invention further provides a method for preparing a negative electrode plate, please refer to fig. 2, where the method includes:
s101, providing a current collector, wherein a first coating area is arranged on a first surface of the current collector, and a second coating area is arranged on a second surface of the current collector.
The current collector in this embodiment is a copper foil, an aluminum foil, or a foil made of other materials, and this embodiment is not limited specifically, and the current collector is used to collect the current generated by the battery active material so as to form a larger current for outputting to the outside.
S102, a coating is arranged on the surface of the current collector and comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on one side, far away from the current collector, of the first coating.
The first coating layer is composed of a first coating material, and in an alternative embodiment, the first coating material may be applied to the first coating region and the second coating region of the current collector through a coating process. The first coating consists of a first active substance, a second conductive agent and a binder, the first active substance is an active substance with high energy density, and a first coating consisting of the first coating has high energy density, so that the energy density of the negative plate is improved.
And a second coating is arranged on one side of the first coating, which is far away from the current collector, and the second coating is composed of a second coating. The second coating is composed of a second active substance, a first conductive agent and a binder, the first conductive agent is a conductive agent with high conductivity, and a second coating composed of the second coating has high conductivity, so that the conductivity of the negative plate is improved, and the negative plate supports a quick charging function.
In the embodiment of the invention, a first coating is arranged in a first coating area on the first surface and a second coating area on the second surface of the current collector, wherein the first coating comprises a first active material with high energy density, so that the energy density of the negative plate is improved; and a second coating is arranged on one side of the first coating, which is far away from the current collector, wherein the second coating comprises a conductive agent with high conductivity, so that the conductivity of the negative plate is improved. The coating with high energy density and the coating with high conductivity are arranged on the current collector, so that the energy density of the battery is improved on the premise of not losing the quick charging performance of the battery.
The embodiment of the present invention further provides a battery, which includes the above negative electrode plate, and the structure of the negative electrode plate may refer to the above embodiment, which is not described herein again in detail. Since the negative electrode sheet in the above embodiment is used in this embodiment, the battery provided in the embodiment of the present invention has the same advantageous effects as the negative electrode sheet in the above embodiment.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A negative electrode sheet, comprising:
the current collector comprises a current collector body, a first coating area is arranged on the first surface of the current collector body, and a second coating area is arranged on the second surface of the current collector body;
the coating comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on one side, far away from the current collector, of the first coating;
the first coating comprises a first active substance for improving the energy density of the negative plate, and the second coating comprises a first conductive agent for improving the conductivity of the negative plate.
2. The negative electrode sheet of claim 1, wherein the first coating comprises a second conductive agent, and in the case that the first conductive agent and the second conductive agent are both tubular conductive agents, the first wall thickness of the first conductive agent is greater than or equal to the second wall thickness of the second conductive agent.
3. The negative plate of claim 2, wherein the wall value is less than a first predetermined value and greater than a second predetermined value, the first predetermined value being greater than the second predetermined value;
the pipe wall value is the product of the first pipe wall thickness and the thickness of a first target coating, divided by the product of the second pipe wall thickness and the thickness of a second target coating;
wherein the first target coating is the thicker of the first and second coatings and the second target coating is the thinner of the first and second coatings.
4. Negative electrode sheet according to claim 1, characterized in that the ratio of the thickness of the first coating layer to the thickness of the second coating layer is between 1:9 and 9: 1.
5. The negative electrode sheet according to claim 1, wherein the first coating material comprises a first active material, a second conductive agent, and a binder, the first active material comprises first graphite, the second conductive agent comprises at least one of carbon black, carbon nanotubes, and graphene, and the binder comprises at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber-based compounds, and polyacrylate-based compounds.
6. The negative electrode sheet according to claim 1, wherein the first conductive agent comprises graphyne, and a content of the graphyne in the first conductive agent is not more than 40%.
7. The negative electrode sheet according to claim 1, wherein the second coating material comprises a second active material, a first conductive agent, and a binder, the second active material comprises a second graphite, the first conductive agent comprises graphdine and at least one of carbon black, carbon nanotubes, and graphene, and the binder comprises at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber-based compounds, and polyacrylate-based compounds.
8. The negative electrode sheet according to claim 1, wherein a deintercalation rate of lithium ions of the second coating layer is greater than a deintercalation rate of lithium ions of the first coating layer.
9. A preparation method of a negative plate is characterized by comprising the following steps:
providing a current collector, wherein a first surface of the current collector is provided with a first coating area, and a second surface of the current collector is provided with a second coating area;
providing a coating on the surface of the current collector, wherein the coating comprises a first coating formed by a first coating and a second coating formed by a second coating, the first coating is arranged in a first coating area and a second coating area of the current collector, and the second coating is arranged on the side, away from the current collector, of the first coating;
the first coating comprises a first active substance for improving the energy density of the negative plate, and the second coating comprises a first conductive agent for improving the conductivity of the negative plate.
10. A battery comprising the negative electrode sheet according to any one of claims 1 to 8.
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