CN112103469B - Silicon-carbon negative electrode plate, preparation method thereof and lithium ion battery - Google Patents

Silicon-carbon negative electrode plate, preparation method thereof and lithium ion battery Download PDF

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CN112103469B
CN112103469B CN202011000830.6A CN202011000830A CN112103469B CN 112103469 B CN112103469 B CN 112103469B CN 202011000830 A CN202011000830 A CN 202011000830A CN 112103469 B CN112103469 B CN 112103469B
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negative electrode
carbon
silicon
carbon negative
parts
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CN112103469A (en
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尚德华
杨泽乾
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Aopu Shanghai New Energy Co Ltd
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    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
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    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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Abstract

The invention is suitable for the technical field of lithium ion batteries, and provides a silicon-carbon negative pole piece, a preparation method thereof and a lithium ion battery, wherein the silicon-carbon negative pole piece comprises the following components: a current collector; a first carbon negative electrode layer disposed on the current collector; a primary material layer disposed on the current collector; the main material layer comprises a silicon-carbon negative electrode area with a pit structure and a carbon negative electrode area filled in the pit structure; and a second carbon negative electrode layer disposed on the main material layer. The elastic conductive agent is uniformly dispersed and wrapped on the surface of the silicon-carbon material particles, so that the silicon-carbon material has a buffering effect when expanding. In addition, the invention adopts the gravure coating technology, the silicon-carbon material and the lithium-containing salt carbon material are distributed at intervals, the lithium salt can supplement lithium for the silicon-carbon material and form an SEI film, the carbon material provides buffer for volume expansion of the silicon-carbon material, and the problems of low first efficiency and expansion fracture of the silicon-carbon material can be solved at the same time.

Description

Silicon-carbon negative electrode plate, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a silicon-carbon negative electrode plate, a preparation method thereof and a lithium ion battery.
Background
In the field of secondary batteries, lithium ion batteries are widely applied to the fields of new energy vehicles, energy storage systems, consumer electronics and the like due to the excellent characteristics of environmental protection, high energy power density, high working voltage and the like. A negative electrode, which is one of the major components of the lithium ion battery 4, is mainly made of a graphite-based carbon material for many years. However, the theoretical gram capacity of 372mAh/g can not meet the requirement of high energy density, so that the novel high-specific-capacity material is widely researched. The silicon negative electrode has the theoretical specific capacity as high as 4200mAh/g, low lithium intercalation voltage and rich reserves, and is expected to replace graphite to become a next-generation negative electrode material. However, when silicon is used as a negative electrode material, the problems of huge volume expansion after lithium intercalation, easy material peeling, pulverization, SEI film cracking, low first effect and the like exist, and the problem of silicon-carbon mixing can be alleviated to a certain extent, but the problem can not be effectively solved. For silicon carbon negative electrodes, the prior art is mainly divided into three types: 1. coating, namely coating a layer of carbon material on the surface of the silicon material to form a core-shell structure which can inhibit the pulverization of the silicon material or coating a layer of protective film similar to SEI on the surface of the silicon carbon material to inhibit the expansion and cracking of the material; 2. the pole piece buffer layer is formed by coating a graphite layer silicon-carbon cathode volume expansion buffer layer on the silicon-carbon cathode so as to increase the elasticity of the pole piece; 3. and pre-lithiation, namely pre-supplementing lithium by adding lithium powder into the porous lithium foil or the silicon-carbon cathode slurry, so that the first efficiency of the silicon-carbon cathode can be improved, and the loss of irreversible capacity is reduced.
Silicon is the most promising next-generation material to replace graphite, and researchers have conducted a lot of research and technical development for the early commercialization of silicon, and through many years of trials, silicon-carbon mixed as a negative electrode is an effective method for improving the electrochemical performance of a silicon-based negative electrode lithium ion battery, and other technical schemes are supplemented so that the silicon-carbon negative electrode lithium ion battery can meet the commercial application.
The prior technical scheme has certain disadvantages. For example, a coating method, doping and coating are common application methods for improving material performance, a carbon material protective layer is coated on the surface of a silicon material, the silicon material is required to be firstly prepared into a nanometer level and then coated, the technical difficulty is high, the process is complex, and although the volume expansion of the silicon is inhibited to a certain extent, the problem of silicon breakage after long-time circulation still exists. The pole piece buffer layer method is characterized in that a graphite buffer layer is coated on the surface of the silicon-carbon negative electrode, the expansion of the pole piece layer is weakened, but the expansion of the silicon material layer still exists, the improvement is very limited, and the problems of pulverization, SEI (solid electrolyte interphase) cracking and the like still exist. The pre-lithiation method, whether adding lithium foil to the silicon-carbon negative plate or adding lithium powder or other lithium supplement agents to the silicon-carbon slurry, greatly increases the manufacturing process difficulty and cost, and cannot solve the problem of expansion of the silicon material.
Disclosure of Invention
The embodiment of the invention aims to provide a silicon-carbon negative pole piece and aims to solve the problems in the background technology.
The embodiment of the invention is realized in such a way that the silicon-carbon negative pole piece comprises:
a current collector;
a first carbon negative electrode layer disposed on the current collector;
a primary material layer disposed on the current collector; the main material layer comprises a silicon-carbon negative electrode area with a pit structure and a carbon negative electrode area filled in the pit structure; and
a second carbon negative electrode layer disposed on the main material layer;
the silicon-carbon negative electrode region comprises the following components in parts by weight: 90.5-97.5 parts of silicon carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent and 0.8-3.6 parts of binder;
the carbon negative electrode region comprises the following components in parts by weight: 90.5-97.5 parts of carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent, 0.8-3.6 parts of binder and 1-5 parts of lithium salt;
the first carbon negative electrode layer and the second carbon negative electrode layer respectively comprise the following components in parts by weight: 90.5-97.5 parts of carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent and 0.8-3.6 parts of binder.
As a preferable scheme of the embodiment of the invention, the silicon-carbon negative electrode region comprises the following components in parts by weight: 93-95 parts of silicon carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent and 2-3 parts of binder.
As another preferable scheme of the embodiment of the invention, the carbon negative electrode region comprises the following components in parts by weight: 93-95 parts of carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent, 2-3 parts of binder and 2-4 parts of lithium salt.
As another preferable scheme of the embodiment of the invention, the first carbon negative electrode layer and the second carbon negative electrode layer each include the following components in parts by weight: 93-95 parts of carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent and 2-3 parts of binder.
As another preferable scheme of the embodiment of the present invention, the conductive agents are at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, conductive graphite, conductive carbon black, and carbon fibers; and the conductive agent in the silicon-carbon negative electrode region contains at least one carbon nano tube.
As another preferable scheme of the embodiment of the invention, the thickener is sodium carboxymethyl cellulose; the binder is at least one of polyacrylic acid, polyvinyl alcohol, styrene butadiene rubber and acrylonitrile.
In another preferred embodiment of the present invention, the lithium salt is lithium hydroxide, lithium carbonate, lithium fluoride, lithium oxalate, CH3CH2OCO2Li、CH3CH2OLi、CH3At least one of COOLi.
Another object of the embodiments of the present invention is to provide a method for preparing the silicon-carbon negative electrode plate, which includes the following steps:
weighing a silicon-carbon material, a conductive agent, a thickening agent and a binder according to the weight parts of the components in the silicon-carbon negative electrode area, mixing the silicon-carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water to prepare silicon-carbon negative electrode slurry with the solid content of 40-60%;
weighing a carbon material, a conductive agent, a thickening agent, a binder and a lithium salt according to the weight parts of the components in the carbon negative electrode area, mixing the lithium salt with one solvent of water, benzene and ethanol to obtain a lithium salt solution, mixing the carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water and the lithium salt solution to prepare a first carbon negative electrode slurry with the solid content of 40-60%;
weighing a carbon material, a conductive agent, a thickening agent and a binder according to the weight parts of the components in the carbon negative electrode area, mixing the carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water to prepare second carbon negative electrode slurry with the solid content of 40-60%;
coating second carbon negative electrode slurry on a current collector to form a first carbon negative electrode layer on the current collector;
coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area with a pit structure;
coating first carbon cathode slurry on the silicon-carbon cathode region by adopting a gravure printing method, filling a pit structure on the silicon-carbon cathode region, and forming a carbon cathode region to obtain a main material layer;
and coating second carbon negative electrode slurry on the main material layer to form a second carbon negative electrode layer on the main material layer, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode piece.
The embodiment of the invention also aims to provide the silicon-carbon negative electrode plate prepared by the preparation method.
Another objective of the embodiments of the present invention is to provide a lithium ion battery, which includes a positive electrode plate, an electrolyte, and the silicon-carbon negative electrode plate.
In the present invention:
the first carbon negative layer plays a role in buffering expansion of silicon carbon in the main direction of the current collector, enhances the binding force with the current collector and is not easy to fall off. And the second carbon cathode layer plays a role in buffering the expansion of the silicon carbon to the direction of the diaphragm and preventing the silicon carbon cathode from falling powder and polluting the diaphragm. The carbon cathode region in the transverse direction of the silicon-carbon cathode acts as a transverse expansion buffer and enhances the conductivity of the main material layer. The silicon-carbon cathode adopts a carbon nanotube long-arm conductive agent, and electrons still exist among particles after the silicon-carbon cathode expands so as to ensure the conductivity. In addition, lithium salt added in the carbon negative electrode region can permeate into the silicon-carbon negative electrode region, an SEI film is formed after baking, and the SEI film is in a stable state after formation, so that the loss of lithium is supplemented, and the first efficiency of the battery is improved.
According to the silicon-carbon negative electrode piece provided by the embodiment of the invention, the elastic conductive agent is uniformly dispersed and wrapped on the surface of the silicon-carbon material particles, so that the silicon-carbon material has a buffering effect when expanding. In addition, the silicon-carbon material is coated for the first time, the carbon cathode slurry containing lithium salt is coated for the second time by adopting a multiple coating technology, the silicon-carbon material and the carbon material containing lithium salt are distributed at intervals by adopting a gravure coating technology, the lithium salt can supplement lithium for the silicon-carbon material and form an SEI film, the carbon material provides volume expansion buffer for the silicon-carbon material, and the problems of low first effect and expansion fracture of the silicon-carbon material can be solved at the same time; the preparation method of the silicon-carbon negative pole piece provided by the embodiment of the invention has the advantages of simple process and low cost.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-carbon negative electrode tab according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an expanded steric buffer of the silicon-carbon negative electrode region according to an embodiment of the present invention.
In the figure: 1-current collector, 2-first carbon cathode layer, 3-main material layer, 4-second carbon cathode layer, 5-silicon carbon cathode region and 6-carbon cathode region.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.
Example 1
As shown in fig. 1-2, the embodiment provides a silicon-carbon negative electrode plate, and the preparation method thereof includes the following steps:
s1, weighing 95.5kg of silicon carbon material, 1kg of single-walled carbon nanotube, 1.5kg of sodium carboxymethylcellulose and 2kg of styrene butadiene rubber, mixing the silicon carbon material, the single-walled carbon nanotube, the sodium carboxymethylcellulose and the styrene butadiene rubber, and then adding deionized water to prepare silicon carbon negative electrode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
S2, weighing 95.5kg of artificial graphite, 1kg of single-walled carbon nanotube, 1.5kg of sodium carboxymethylcellulose, 2kg of styrene butadiene rubber and 3kg of lithium carbonate, mixing lithium carbonate and water to obtain a lithium salt solution, then mixing the artificial graphite, the single-walled carbon nanotube, the sodium carboxymethylcellulose and the styrene butadiene rubber, and then adding deionized water and the lithium salt solution to prepare the first carbon cathode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
S3, weighing 96.5kg of artificial graphite, 0.5kg of carbon black, 1.5kg of sodium carboxymethylcellulose and 2kg of styrene butadiene rubber, mixing the artificial graphite, the carbon black, the sodium carboxymethylcellulose and the styrene butadiene rubber, and adding deionized water to prepare second carbon negative electrode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
And S4, taking the copper foil as a current collector 1, and uniformly coating the second carbon negative electrode slurry on the current collector 1 to form a first carbon negative electrode layer 2 with the thickness of 5 microns on the current collector 1.
And S5, coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer 2 in a distributed manner by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area 5 with a large uniform pit structure.
And S6, coating the first carbon negative electrode slurry on the silicon-carbon negative electrode area 5 by adopting a gravure printing method, filling the pit structure on the silicon-carbon negative electrode area 5, forming a carbon negative electrode area 6, and obtaining the main material layer 3.
And S7, uniformly coating second carbon negative electrode slurry on the main material layer 3 to form a second carbon negative electrode layer 4 with the thickness of 10 microns on the main material layer 3, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode plate.
Example 2
The difference between this embodiment and embodiment 1 is that the conductive agents of the first carbon negative electrode paste and the second carbon negative electrode paste are replaced by multi-walled carbon nanotubes.
Example 3
The present embodiment is different from embodiment 1 in that the conductive agents of the silicon-carbon negative electrode slurry, the first carbon negative electrode slurry, and the second carbon negative electrode slurry are replaced with conductive carbon black.
Example 4
As shown in fig. 1-2, the embodiment provides a silicon-carbon negative electrode plate, and the preparation method thereof includes the following steps:
s1, weighing 90.5kg of silicon carbon material, 3kg of multi-walled carbon nanotube, 3kg of sodium carboxymethyl cellulose and 3.6kg of polyacrylic acid, mixing the silicon carbon material, the multi-walled carbon nanotube, the sodium carboxymethyl cellulose and the polyacrylic acid, and then adding deionized water to prepare silicon carbon negative electrode slurry with the solid content of 40% and the viscosity of 2000mP & S for later use.
S2, weighing 90.5kg of artificial graphite, 3kg of graphene, 3kg of sodium carboxymethyl cellulose, 3.6kg of polyacrylic acid and 5kg of lithium hydroxide, mixing lithium hydroxide and benzene to obtain a lithium salt solution, then mixing the artificial graphite, the graphene, the sodium carboxymethyl cellulose and the polyacrylic acid, and adding deionized water and the lithium salt solution to prepare the first carbon cathode slurry with the solid content of 40% and the viscosity of 2000mP & S for later use.
S3, weighing 90.5kg of artificial graphite, 3kg of graphene, 3kg of sodium carboxymethylcellulose and 3.6kg of polyacrylic acid, mixing the artificial graphite, the graphene, the sodium carboxymethylcellulose and the polyacrylic acid, and then adding deionized water to prepare a second carbon cathode slurry with the solid content of 40% and the viscosity of 2000mP & S for later use.
And S4, taking the copper foil as a current collector 1, and uniformly coating the second carbon negative electrode slurry on the current collector 1 to form a first carbon negative electrode layer 2 with the thickness of 0.5 mu m on the current collector 1.
And S5, coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer 2 in a distributed manner by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area 5 with a large uniform pit structure.
And S6, coating the first carbon negative electrode slurry on the silicon-carbon negative electrode area 5 by adopting a gravure printing method, filling the pit structure on the silicon-carbon negative electrode area 5, forming a carbon negative electrode area 6, and obtaining the main material layer 3.
And S7, uniformly coating second carbon negative electrode slurry on the main material layer 3 to form a second carbon negative electrode layer 4 with the thickness of 20 microns on the main material layer 3, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode plate.
Example 5
As shown in fig. 1-2, the embodiment provides a silicon-carbon negative electrode plate, and the preparation method thereof includes the following steps:
s1, weighing 97.5kg of silicon carbon material, 0.1kg of single-walled carbon nanotube, 0.1kg of carbon fiber, 0.8kg of sodium carboxymethyl cellulose, 0.4kg of polyvinyl alcohol and 0.4kg of acrylonitrile, mixing the silicon carbon material, the single-walled carbon nanotube, the carbon fiber, the sodium carboxymethyl cellulose, the polyvinyl alcohol and the acrylonitrile, and adding deionized water to prepare silicon carbon negative electrode slurry with solid content of 60% and viscosity of 6000mP & S for later use.
S2, weighing 97.5kg of artificial graphite, 0.1kg of conductive graphite, 0.1kg of carbon fiber, 0.8kg of sodium carboxymethylcellulose, 0.8kg of acrylonitrile, 0.5kg of lithium fluoride and 0.5kg of lithium oxalate, mixing lithium oxalate, lithium fluoride and ethanol to obtain a lithium salt solution, mixing the artificial graphite, the conductive graphite, the carbon fiber, the sodium carboxymethylcellulose and the acrylonitrile, and adding deionized water and the lithium salt solution to prepare the first carbon cathode slurry with the solid content of 60% and the viscosity of 6000mP & S for later use.
S3, weighing 97.5kg of artificial graphite, 0.2kg of carbon fiber, 0.8kg of sodium carboxymethylcellulose and 0.8kg of acrylonitrile, mixing the artificial graphite, the carbon fiber, the sodium carboxymethylcellulose and the acrylonitrile, and adding deionized water to prepare second carbon cathode slurry with solid content of 60% and viscosity of 6000mP & S for later use.
And S4, taking a copper foil as a current collector 1, and uniformly coating the second carbon negative electrode slurry on the current collector 1 to form a first carbon negative electrode layer 2 with the thickness of 20 microns on the current collector 1.
And S5, coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer 2 in a distributed manner by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area 5 with a large uniform pit structure.
And S6, coating the first carbon negative electrode slurry on the silicon-carbon negative electrode area 5 by adopting a gravure printing method, filling the pit structure on the silicon-carbon negative electrode area 5, forming a carbon negative electrode area 6, and obtaining the main material layer 3.
And S7, uniformly coating second carbon negative electrode slurry on the main material layer 3 to form a second carbon negative electrode layer 4 with the thickness of 0.5 mu m on the main material layer 3, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode piece.
Example 6
As shown in fig. 1-2, the embodiment provides a silicon-carbon negative electrode plate, and the preparation method thereof includes the following steps:
s1, weighing 95kg of silicon carbon material, 1kg of single-walled carbon nanotube, 1kg of sodium carboxymethyl cellulose and 2kg of styrene butadiene rubber, mixing the silicon carbon material, the single-walled carbon nanotube, the sodium carboxymethyl cellulose and the styrene butadiene rubber, and adding deionized water to prepare silicon carbon negative electrode slurry with solid content of 50% and viscosity of 4000mP & S for later use.
S2, weighing 95kg of artificial graphite, 1kg of single-walled carbon nanotube, 1kg of sodium carboxymethyl cellulose, 2kg of styrene butadiene rubber and CH3CH2OCO2Li 1kg、CH3CH2OLi 1kg, CH first3CH2OCO2Li、CH3CH2Mixing OLi with water to obtain a lithium salt solution, then mixing artificial graphite, a single-walled carbon nanotube, sodium carboxymethylcellulose and styrene butadiene rubber, and then adding deionized water and the lithium salt solution to prepare a first carbon cathode slurry with the solid content of 50% and the viscosity of 4000mP & s for later use.
S3, weighing 95kg of artificial graphite, 1kg of carbon black, 1kg of sodium carboxymethylcellulose and 2kg of styrene butadiene rubber, mixing the artificial graphite, the carbon black, the sodium carboxymethylcellulose and the styrene butadiene rubber, and adding deionized water to prepare a second carbon cathode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
And S4, taking the copper foil as a current collector 1, and uniformly coating the second carbon negative electrode slurry on the current collector 1 to form a first carbon negative electrode layer 2 with the thickness of 5 microns on the current collector 1.
And S5, coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer 2 in a distributed manner by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area 5 with a large uniform pit structure.
And S6, coating the first carbon negative electrode slurry on the silicon-carbon negative electrode area 5 by adopting a gravure printing method, filling the pit structure on the silicon-carbon negative electrode area 5, forming a carbon negative electrode area 6, and obtaining the main material layer 3.
And S7, uniformly coating second carbon negative electrode slurry on the main material layer 3 to form a second carbon negative electrode layer 4 with the thickness of 10 microns on the main material layer 3, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode plate.
Example 7
As shown in fig. 1-2, the embodiment provides a silicon-carbon negative electrode plate, and the preparation method thereof includes the following steps:
s1, weighing 93kg of silicon carbon material, 2kg of single-walled carbon nanotube, 2kg of sodium carboxymethyl cellulose and 3kg of styrene butadiene rubber, mixing the silicon carbon material, the single-walled carbon nanotube, the sodium carboxymethyl cellulose and the styrene butadiene rubber, and adding deionized water to prepare silicon carbon negative electrode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
S2, weighing 93kg of artificial graphite, 2kg of single-walled carbon nanotube, 2kg of sodium carboxymethylcellulose, 3kg of styrene butadiene rubber and CH3CH2OCO2Li 2kg、CH3COOLi 2kg, CH first3CH2OCO2Li、CH3And mixing COO Li with water to obtain a lithium salt solution, then mixing artificial graphite, the single-walled carbon nanotube, sodium carboxymethylcellulose and styrene butadiene rubber, and then adding deionized water and the lithium salt solution to prepare first carbon cathode slurry with the solid content of 50% and the viscosity of 4000mP & s for later use.
S3, weighing 93kg of artificial graphite, 2kg of carbon black, 2kg of sodium carboxymethylcellulose and 3kg of styrene butadiene rubber, mixing the artificial graphite, the carbon black, the sodium carboxymethylcellulose and the styrene butadiene rubber, and adding deionized water to prepare a second carbon negative electrode slurry with the solid content of 50% and the viscosity of 4000mP & S for later use.
And S4, taking the copper foil as a current collector 1, and uniformly coating the second carbon negative electrode slurry on the current collector 1 to form a first carbon negative electrode layer 2 with the thickness of 5 microns on the current collector 1.
And S5, coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer 2 in a distributed manner by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area 5 with a large uniform pit structure.
And S6, coating the first carbon negative electrode slurry on the silicon-carbon negative electrode area 5 by adopting a gravure printing method, filling the pit structure on the silicon-carbon negative electrode area 5, forming a carbon negative electrode area 6, and obtaining the main material layer 3.
And S7, uniformly coating second carbon negative electrode slurry on the main material layer 3 to form a second carbon negative electrode layer 4 with the thickness of 10 microns on the main material layer 3, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode plate.
Comparative example 1
The present comparative example differs from example 1 in that the main material layer is coated only with the silicon-carbon negative electrode slurry, i.e., does not include the carbon negative electrode region.
Comparative example 2
This comparative example differs from example 3 in that the main material layer was coated only with the silicon-carbon negative electrode slurry, i.e., no carbon negative electrode region was included.
Experimental example:
firstly, taking the silicon-carbon negative electrode plates of the embodiments 1 to 3 and the comparative examples 1 to 2, taking a lithium plate as a counter electrode, manufacturing 2016 type button cells, charging and discharging at 0.2C, and calculating the first efficiency of the silicon-carbon negative electrode plates, wherein the results are shown in the following table 1.
TABLE 1
Item Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2
First time efficiency 91.2％ 92.0％ 90.7％ 86.4％ 85.7％
Taking the silicon-carbon negative pole pieces of the embodiments 1-3 and the comparative examples 1-2, taking the lithium iron phosphate positive pole piece as a positive pole piece, laminating or winding the silicon-carbon negative pole piece, a diaphragm and the positive pole piece to prepare a bare cell, welding a tab and a shell cover, and then injecting 1M LiPF6The electrolyte is aged and formed, a soft package battery is assembled, after the cycle is 800 times, the expansion thickness of the battery is tested, the expansion rate is calculated, and the result is shown in the following table 2.
TABLE 2
Item Example one Example two EXAMPLE III Comparative example 1 Comparative example No. two
Expansion ratio 19.02％ 16.68％ 20.52％ 21.44％ 24.55％
In summary, the invention can effectively improve the first effect and the overall expansion of the battery by adding the transverse carbon negative electrode material lithium supplement buffer layer, wherein the conductive agent uses the multiwalled carbon nanotube, and the performance of the silicon-carbon negative electrode plate is also improved.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. The utility model provides a silicon carbon negative pole piece, includes the mass flow body, its characterized in that still includes:
a first carbon negative electrode layer disposed on the current collector;
a main material layer disposed on the first carbon negative electrode layer; the main material layer comprises a silicon-carbon negative electrode area with a pit structure and a carbon negative electrode area filled in the pit structure; and
a second carbon negative electrode layer disposed on the main material layer;
the silicon-carbon negative electrode region comprises the following components in parts by weight: 90.5-97.5 parts of silicon carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent and 0.8-3.6 parts of binder;
the carbon negative electrode region comprises the following components in parts by weight: 90.5-97.5 parts of carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent, 0.8-3.6 parts of binder and 1-5 parts of lithium salt;
the first carbon negative electrode layer and the second carbon negative electrode layer respectively comprise the following components in parts by weight: 90.5-97.5 parts of carbon material, 0.2-3 parts of conductive agent, 0.8-3 parts of thickening agent and 0.8-3.6 parts of binder.
2. The silicon-carbon negative electrode plate as claimed in claim 1, wherein the silicon-carbon negative electrode region comprises the following components in parts by weight: 93-95 parts of silicon carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent and 2-3 parts of binder.
3. The silicon-carbon negative electrode plate as claimed in claim 1, wherein the carbon negative electrode region comprises the following components in parts by weight: 93-95 parts of carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent, 2-3 parts of binder and 2-4 parts of lithium salt.
4. The silicon-carbon negative electrode plate as claimed in claim 3, wherein the first carbon negative electrode layer and the second carbon negative electrode layer each comprise the following components in parts by weight: 93-95 parts of carbon material, 1-2 parts of conductive agent, 1-2 parts of thickening agent and 2-3 parts of binder.
5. The silicon-carbon negative electrode plate as claimed in any one of claims 1 to 4, wherein the conductive agent is at least one of single-walled carbon nanotube, multi-walled carbon nanotube, graphene, conductive graphite, conductive carbon black and carbon fiber; and the conductive agent in the silicon-carbon negative electrode region contains at least one carbon nano tube.
6. The silicon-carbon negative electrode plate as claimed in any one of claims 1 to 4, wherein the thickener is sodium carboxymethylcellulose; the binder is at least one of polyacrylic acid, polyvinyl alcohol, styrene butadiene rubber and acrylonitrile.
7. The silicon-carbon negative electrode plate as claimed in claim 1 or 3, wherein the lithium salt is lithium hydroxide, lithium carbonate, lithium fluoride, lithium oxalate, CH3CH2OCO2Li、CH3CH2OLi、CH3At least one of COOLi.
8. The preparation method of the silicon-carbon negative electrode plate as claimed in any one of claims 1 to 7, characterized by comprising the following steps:
weighing a silicon-carbon material, a conductive agent, a thickening agent and a binder according to the weight parts of the components in the silicon-carbon negative electrode area, mixing the silicon-carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water to prepare silicon-carbon negative electrode slurry with the solid content of 40-60%;
weighing a carbon material, a conductive agent, a thickening agent, a binder and a lithium salt according to the weight parts of the components in the carbon negative electrode area, mixing the lithium salt with one solvent of water, benzene and ethanol to obtain a lithium salt solution, mixing the carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water and the lithium salt solution to prepare a first carbon negative electrode slurry with the solid content of 40-60%;
weighing a carbon material, a conductive agent, a thickening agent and a binder according to the weight parts of the components in the first carbon negative electrode layer and the second carbon negative electrode layer, mixing the carbon material, the conductive agent, the thickening agent and the binder, and then adding deionized water to prepare second carbon negative electrode slurry with the solid content of 40-60%;
coating second carbon negative electrode slurry on a current collector to form a first carbon negative electrode layer on the current collector;
coating silicon-carbon negative electrode slurry on the first carbon negative electrode layer by adopting a gravure printing method, and drying to form a silicon-carbon negative electrode area with a pit structure;
coating first carbon cathode slurry on the silicon-carbon cathode region by adopting a gravure printing method, filling a pit structure on the silicon-carbon cathode region, and forming a carbon cathode region to obtain a main material layer;
and coating second carbon negative electrode slurry on the main material layer to form a second carbon negative electrode layer on the main material layer, and then drying, rolling and cutting to obtain the silicon-carbon negative electrode piece.
9. The silicon-carbon negative electrode plate prepared by the preparation method of claim 8.
10. A lithium ion battery, which comprises a positive plate and an electrolyte, and is characterized by further comprising the silicon-carbon negative plate as claimed in any one of claims 1 to 7 and 9.
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