CN111463401B - Lithium ion battery cathode and preparation method thereof - Google Patents

Lithium ion battery cathode and preparation method thereof Download PDF

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CN111463401B
CN111463401B CN202010232692.8A CN202010232692A CN111463401B CN 111463401 B CN111463401 B CN 111463401B CN 202010232692 A CN202010232692 A CN 202010232692A CN 111463401 B CN111463401 B CN 111463401B
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negative electrode
active material
agent
binder
lithium ion
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CN111463401A (en
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於志锋
彭冲
李俊义
徐延铭
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Zhuhai Cosmx Battery Co Ltd
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
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    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
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    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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Abstract

A lithium ion battery cathode and a preparation method thereof belong to the technical field of lithium ion batteries, and the specific scheme is as follows: a lithium ion battery cathode comprises a cathode current collector and a cathode coating, wherein the cathode coating comprises a bottom layer and a top layer, the bottom layer is coated on two surfaces of the cathode current collector, the top layer is coated on the bottom layer, the top layer comprises a negative electrode active material I, a conductive agent, a thickening agent I, a dispersing agent I and a binder I, the bottom layer comprises a negative electrode active material II, a conductive agent, a thickening agent II, a dispersing agent II and a binder II, the viscosity of the thickening agent I is greater than that of the thickening agent II, the viscosity of the dispersing agent I is greater than that of the dispersing agent II, the elastic modulus of the binder I is larger than that of the binder II, a high-viscosity thickening agent I, a high-viscosity dispersing agent I and a high-elastic-modulus binder I are used in the negative electrode slurry A, the use amounts of the thickening agent I, the dispersing agent I and the binder I are reduced, and the use amount of the conductive agent is increased, so that the dynamic performance of the top layer of the negative electrode is improved.

Description

Lithium ion battery cathode and preparation method thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery cathode and a preparation method thereof.
Background
The traditional lithium ion battery has the defects of fast capacity attenuation, short cycle life, large thickness expansion rate, easy lithium precipitation and the like in the charging and discharging processes, so that the application of the traditional lithium ion battery is severely limited.
Disclosure of Invention
The invention provides a lithium ion battery cathode for improving the cycle performance of a lithium ion battery.
The second purpose of the invention is to provide a preparation method of the lithium ion battery cathode.
The utility model provides a lithium ion battery negative pole, includes the negative pole mass flow body and negative coating, the negative coating includes bottom and top layer, the bottom coating is on two surfaces of the negative pole mass flow body, the top layer coating is on the bottom, the top layer includes negative pole active material I, conductive agent, thickener I, dispersant I and binder I, the bottom includes negative pole active material II, conductive agent, thickener II, dispersant II and binder II, the viscosity of thickener I is greater than thickener II, the viscosity of dispersant I is greater than dispersant II, the elastic modulus of binder I is greater than binder II.
Furthermore, the thickening agent I and the thickening agent II are the same substance, the dispersing agent I and the dispersing agent II are the same substance, and the binder I and the binder II are the same substance.
Further, the gram capacity of the negative electrode active material I is smaller than that of the negative electrode active material II.
Preferably, the negative electrode active material I and the negative electrode active material II are both silicon-carbon negative electrode active materials.
Preferably, the thickening agent I, the thickening agent II, the dispersing agent I and the dispersing agent II are all sodium carboxymethylcellulose, and the viscosity of the thickening agent I and the viscosity of the dispersing agent I are all more than or equal to 18000mPa.S at the temperature of 25 +/-5 ℃ and when the solid content is 1.3%; when the solid content of the thickening agent II and the dispersing agent II is 1.3 percent at the temperature of 25 +/-5 ℃, the viscosity of the thickening agent II and the dispersing agent II is less than or equal to 15000 mPa.S.
Preferably, the binder I and the binder II are styrene butadiene rubber, the elastic modulus of the binder I is more than or equal to 30MPa when the solid content of the binder I is 40% at 25 +/-5 ℃, and the elastic modulus of the binder II is less than or equal to 15MPa when the solid content of the binder II is 40% at 25 +/-5 ℃.
Further, the top layer also comprises ethylene carbonate.
Further, the thickness of the bottom layer on any side surface of the negative electrode current collector is 37.5-60 μm, and the thickness of the top layer is 37.5-60 μm.
The preparation method of the lithium ion battery cathode comprises the following steps:
s1: uniformly dispersing a negative electrode active material I, a conductive agent, a thickening agent I, a dispersing agent I and a binder I in a solvent to prepare negative electrode slurry A, and uniformly dispersing a negative electrode active material II, a conductive agent, a thickening agent II, a dispersing agent II and a binder II in a solvent to prepare negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector to form a bottom layer, and then coating the negative electrode slurry A on the bottom layer to form a top layer; or coating the negative electrode slurry B and the negative electrode slurry A on one side of the negative electrode current collector at the same time, and then coating the negative electrode slurry B and the negative electrode slurry A on the other side of the negative electrode current collector at the same time, wherein the negative electrode slurry B is coated on the negative electrode current collector to form a bottom layer, and the negative electrode slurry A is coated on the negative electrode slurry B to form a top layer;
s3: and drying the negative current collectors coated with the negative slurry A and the negative slurry B to remove the solvent, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
Further, in S1, ethylene carbonate is further added to the negative electrode slurry a.
The specific technical scheme is as follows:
the invention has the beneficial effects that:
according to the invention, through two coating processes, two layers of different types of slurry are respectively coated on two sides of a negative current collector to regulate and control the liquid absorption performance and the dynamic performance of different coating layers of a negative pole piece of the lithium ion battery, especially, the negative slurry A is prepared by using a high-viscosity thickening agent I, a high-viscosity dispersing agent I and a high-elasticity-modulus binder I, so that the consumption of the thickening agent I, the dispersing agent I and the binder I is reduced, the consumption of a conductive agent is increased, and the dynamic performance of the top layer of the negative pole piece is better; the gram capacity of the negative electrode active material I is low, the rate capability is good, and the safety of lithium precipitation is high; when the negative active material is a silicon-carbon negative active material, the negative pole piece has smaller volume effect and higher safety. The surface resistance and the porosity of the top layer of the negative pole piece are superior to those of the bottom layer, the polarization effect between the top layer of the negative pole and the corresponding diaphragm is improved, and the liquid absorption performance of the top layer of the negative pole is improved, so that the cycle performance of the lithium ion battery is improved.
Drawings
FIG. 1: a schematic structural diagram of a negative pole piece;
in the figure: 1. bottom layer, 2, top layer, 3, negative current collector, 4, long plaster layer, 5, short plaster layer.
Detailed Description
The technical solutions of the present invention are further described below by the specific embodiments, but not limited thereto, and modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
The "conductive agent" and "solvent" referred to in the following embodiments are all conventional materials in lithium ion batteries; the related 'drying, rolling, slitting and flaking' are all conventional technical means for preparing the lithium ion battery in the field.
Detailed description of the invention
The utility model provides a lithium ion battery negative pole, includes the negative pole mass flow body 3 and negative coating, the negative coating includes bottom 1 and top layer 2, 1 coating in the bottom is on two surfaces of the negative pole mass flow body 3, top layer 2 coating is on bottom 1, top layer 2 includes negative pole active material I, conductive agent, thickener I, dispersant I and binder I, bottom 1 includes negative pole active material II, conductive agent, thickener II, dispersant II and binder II, the viscosity of thickener I is greater than thickener II, the viscosity of dispersant I is greater than dispersant II, the elastic modulus of binder I is greater than binder II.
Preferably, the thickener I and the thickener II are the same substance, the dispersant I and the dispersant II are the same substance, and the binder I and the binder II are the same substance.
Further, the gram capacity of the negative electrode active material I is smaller than that of the negative electrode active material II.
Further, the thickening agent I, the thickening agent II, the dispersing agent I and the dispersing agent II are all sodium carboxymethylcellulose, and the viscosity of the thickening agent I and the viscosity of the dispersing agent I are all more than or equal to 18000mPa.S at the temperature of 25 +/-5 ℃ and when the solid content is 1.3%; preferably, the viscosity is 18000, 19000 or 20000 mpa.s; when the solid content of the thickening agent II and the dispersing agent II is 1.3 percent at 25 +/-5 ℃, the viscosity is less than or equal to 15000 mPa.S; preferably, the viscosity is 10000 or 13000 mPa.S;
further, the binder I and the binder II are both styrene butadiene rubber, and when the solid content of the binder I is 40% at 25 +/-5 ℃, the elastic modulus of the binder I is more than or equal to 30MPa, preferably the elastic modulus of the binder I is 30, 35 or 40 MPa; the elastic modulus of the adhesive II is less than or equal to 15MPa, preferably 10 or 15MPa, when the solid content is 40% at the temperature of 25 +/-5 ℃.
Preferably, the negative electrode active material I and the negative electrode active material II are silicon-carbon negative electrode active materials, and the silicon-carbon negative electrode active materials are pure silicon/carbon negative electrode materials, silicon oxide/carbon negative electrode materials or lithium-supplementing silicon-carbon negative electrode materials; the negative electrode active material I and the negative electrode active material II are the same in composition.
Furthermore, the top layer 2 comprises a mixture I by mass, wherein a negative active material I accounts for 96.1-97.3%, a conductive agent accounts for 1.2-1.7%, a thickening agent I and a dispersing agent I account for 0.7-1.1%, and a binder I accounts for 0.8-1.1%; in the bottom layer 1, the negative active material II accounts for 96.1-97.3%, the conductive agent accounts for 0.5-1.0%, the thickening agent II and the dispersing agent II account for 1.2-1.5%, and the binder II accounts for 1.0-1.4%.
Furthermore, the top layer 2 also comprises Ethylene Carbonate (EC), wherein the ethylene carbonate accounts for 0.4-0.9% of the mixture I by mass, and the ethylene carbonate has the functions of increasing the porosity of the top layer 2, improving the coating consistency of the slurry of the top layer 2 and properly improving the liquid retention of the battery electrolyte, so that the cycle performance of the battery can be improved.
Further, the length of the negative electrode coating coated on one side surface of the negative electrode current collector 3 is greater than that of the negative electrode coating coated on the other side surface of the negative electrode current collector 3, the long negative electrode coating is a long paste coating 4, and the short negative electrode coating is a short paste coating 5.
Further, the thickness of the bottom layer 1 on any side surface of the negative electrode current collector 3 is 37.5-60 μm, and the thickness of the top layer 2 is 37.5-60 μm.
Detailed description of the invention
A method for preparing a negative electrode of a lithium ion battery according to a first embodiment of the present invention includes the following steps:
s1: uniformly dispersing a negative electrode active material I, a conductive agent, a thickening agent I, a dispersing agent I and a binder I in a solvent to prepare negative electrode slurry A, and uniformly dispersing a negative electrode active material II, a conductive agent, a thickening agent II, a dispersing agent II and a binder II in a solvent to prepare negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector 3 to form a bottom layer 1, and then coating the negative electrode slurry A on the bottom layer 1 to form a top layer 2; or coating the negative electrode slurry B and the negative electrode slurry A on one side of the negative electrode current collector 3 at the same time, and then coating the negative electrode slurry B and the negative electrode slurry A on the other side of the negative electrode current collector 3 at the same time, wherein the negative electrode slurry B is coated on the negative electrode current collector 3 to form a bottom layer 1, and the negative electrode slurry A is coated on the negative electrode slurry B to form a top layer 2;
s3: and drying the negative current collector 3 coated with the negative electrode slurry A and the negative electrode slurry B to remove the solvent, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
Further, in step S1, ethylene carbonate is further added to the negative electrode slurry a.
Furthermore, the solvents in the cathode slurry A and the cathode slurry B are deionized water.
Detailed description of the invention
In a method for preparing a lithium ion battery negative electrode in the second embodiment, in step S1, a specific preparation method of the negative electrode slurry a is as follows:
step 1: uniformly mixing and dispersing 10-40% of the total mass of the thickening agent I and the dispersing agent I and all the conductive agents into a solvent;
step 2: then adding 20-30% of the total mass of the negative active material I and 20-30% of the total mass of the thickening agent I and the dispersing agent I, and uniformly dispersing;
and step 3: adding 20-30% of the total mass of the negative active material I and 30-70% of the total mass of the thickening agent I and the dispersing agent I, and uniformly dispersing;
and 4, step 4: adding 20-30% of the total mass of the negative active material I, and uniformly dispersing;
and 5: adding 10-40% of the total mass of the negative active material I, and uniformly dispersing;
step 6: and finally, completely adding the binder I, uniformly dispersing, adding the EC, and uniformly dispersing to obtain the cathode slurry A.
Detailed description of the invention
In a method for preparing a lithium ion battery negative electrode in the second embodiment, in step S1, a specific preparation method of the negative electrode slurry B is:
step 1: uniformly mixing and dispersing 10-40% of the total mass of the thickening agent II and the dispersing agent II and all the conductive agents into a solvent;
step 2: then adding 20-30% of the total mass of the negative electrode active material II and 20-30% of the total mass of the thickening agent II and the dispersing agent II, and uniformly dispersing;
and step 3: adding 20-30% of the total mass of the negative electrode active material II and 30-70% of the total mass of the thickening agent II and the dispersing agent II, and uniformly dispersing;
and 4, step 4: adding 20-30% of the total mass of the negative active material II, and uniformly dispersing;
and 5: adding 10-40% of the total mass of the negative active material II, and uniformly dispersing;
step 6: and finally, adding the binder II completely, and dispersing uniformly to obtain the cathode slurry B.
Example 1
The negative electrode of the lithium ion battery comprises a negative electrode current collector 3 and a negative electrode coating, wherein the negative electrode coating comprises a bottom layer 1 and a top layer 2, the bottom layer 1 is coated on two surfaces of the negative electrode current collector 3, the coating thickness of a single-layer bottom layer 1 is 38 micrometers, the top layer 2 is coated on the bottom layer 1, and the coating thickness of the single-layer top layer 2 is 60 micrometers; the bottom layer 1 comprises 96.1% by mass of a negative electrode active material II (silicon-carbon negative electrode material or silicon-oxygen/carbon negative electrode material or lithium-supplement silicon-carbon negative electrode material, the gram capacity is 430mAh/g), 1.0% by mass of a conductive agent, 1.5% by mass of sodium carboxymethyl cellulose CMC (the viscosity is 13000mPa.s) and 1.4% by mass of styrene-butadiene rubber SBR (the elastic modulus is 15MPa), the top layer 2 comprises a mixture I, and the mixture I comprises 96.1% by mass of a negative electrode active material I (silicon-carbon negative electrode material or silicon-oxygen/carbon negative electrode material or lithium-supplement silicon-carbon negative electrode material, the gram capacity is 410mAh/g), 1.7% by mass of a conductive agent, 1.1% by mass of sodium carboxymethyl cellulose CMC (the viscosity is 18000mPa.s) and 1.1% by mass of styrene-butadiene rubber SBR (the elastic modulus is 30 MPa); the negative electrode active material I and the negative electrode active material II are the same in composition.
Further, the top layer 2 also comprises ethylene carbonate, and the ethylene carbonate accounts for 0.4% of the mixture I by mass.
The preparation method of the lithium ion battery cathode comprises the following steps:
s1: uniformly dispersing a mixture I consisting of 96.1% by mass of a negative electrode active material I, 1.7% by mass of a conductive agent, 1.1% by mass of CMC (viscosity of 18000mPa.s) and 1.1% by mass of SBR (elastic modulus of 30MPa) and 0.4% by mass of ethylene carbonate accounting for the mixture I in deionized water to prepare a negative electrode slurry A; uniformly dispersing 96.1% by mass of a negative electrode active material II, 1.0% by mass of a conductive agent, 1.5% by mass of CMC (viscosity of 13000mPa.s) and 1.4% by mass of SBR (elastic modulus of 15MPa) in deionized water to prepare a negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector 3 to form a bottom layer 1, and then coating the negative electrode slurry A on the bottom layer 1 to form a top layer 2;
s3: and drying the negative current collector 3 coated with the negative electrode slurry A and the negative electrode slurry B to remove deionized water, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
And (3) matching and winding the negative electrode and the positive electrode → packaging → baking liquid injection → formation → secondary sealing → sorting to obtain the lithium ion battery, wherein the rolling, slitting, sheet making, winding, packaging, baking liquid injection, formation, secondary sealing and sorting are carried out by adopting conventional technical means in the field.
The specific preparation method of the negative electrode slurry A comprises the following steps:
step 1: uniformly mixing and dispersing 10% of the total mass of the CMC (with the viscosity of 18000mPa.s) and all the conductive agent into deionized water;
step 2: then adding 20% of the total mass of the negative electrode active material I and 30% of the total mass of the CMC (viscosity of 18000mPa.s), and uniformly dispersing;
and step 3: adding 30% of the total mass of the negative electrode active material I and 60% of the total mass of the CMC (viscosity of 18000mPa.s), and uniformly dispersing;
and 4, step 4: adding 30% of the total mass of the negative active material I, and uniformly dispersing;
and 5: adding 20% of the total mass of the negative active material I, and uniformly dispersing;
step 6: and finally, completely adding the SBR (with the elastic modulus of 30MPa), uniformly dispersing, adding the EC, and uniformly dispersing to obtain the negative electrode slurry A.
The specific preparation method of the negative electrode slurry B comprises the following steps:
step 1: uniformly mixing and dispersing 10% of the total mass of the CMC (with the viscosity of 13000mPa.s) and all the conductive agents into deionized water;
step 2: then adding 20% of the total mass of the negative electrode active material II and 30% of the total mass of the CMC (viscosity of 13000mPa.s), and uniformly dispersing;
and step 3: adding 30% of the total mass of the negative electrode active material II and 60% of the total mass of the CMC (viscosity of 13000mPa.s), and uniformly dispersing;
and 4, step 4: adding 30% of the total mass of the negative electrode active material II, and uniformly dispersing;
and 5: adding 20% of the total mass of the negative electrode active material II, and uniformly dispersing;
step 6: and finally, completely adding SBR (with the elastic modulus of 15MPa) and uniformly dispersing to obtain the negative electrode slurry B.
Example 2
The negative electrode of the lithium ion battery comprises a negative electrode current collector 3 and a negative electrode coating, wherein the negative electrode coating comprises a bottom layer 1 and a top layer 2, the bottom layer 1 is coated on two surfaces of the negative electrode current collector 3, the coating thickness of a single-layer bottom layer 1 is 38 micrometers, the top layer 2 is coated on the bottom layer 1, and the coating thickness of the single-layer top layer 2 is 60 micrometers; the bottom layer 1 comprises 96.1% by mass of a negative electrode active material II (silicon-carbon negative electrode material or silicon-oxygen/carbon negative electrode material or lithium-supplement silicon-carbon negative electrode material, the gram capacity is 430mAh/g), 1.0% by mass of a conductive agent, 1.5% by mass of sodium carboxymethyl cellulose CMC (the viscosity is 13000mPa.s) and 1.4% by mass of styrene butadiene rubber SBR (the elastic modulus is 15MPa), the top layer 2 comprises a mixture I, and the mixture I comprises 96.1% by mass of a negative electrode active material I (silicon-carbon negative electrode material or silicon-oxygen/carbon negative electrode material or lithium-supplement silicon-carbon negative electrode material, the gram capacity is 410mAh/g), 1.7% by mass of a conductive agent, 1.1% by mass of sodium carboxymethyl cellulose CMC (the viscosity is 19000mPa.s) and 1.1% by mass of styrene butadiene rubber SBR (the elastic modulus is 35 MPa); the negative electrode active material I and the negative electrode active material II are the same in composition.
Further, the top layer 2 also comprises ethylene carbonate, and the ethylene carbonate accounts for 0.4% of the mixture I by mass.
The preparation method of the lithium ion battery cathode comprises the following steps:
s1: uniformly dispersing a mixture I consisting of 96.1% by mass of a negative electrode active material I, 1.7% by mass of a conductive agent, 1.1% by mass of CMC (19000 mPa.s) and 1.1% by mass of SBR (elastic modulus of 35MPa) and 0.4% by mass of ethylene carbonate accounting for the mixture I in deionized water to prepare a negative electrode slurry A; uniformly dispersing 96.1% by mass of a negative electrode active material II, 1.0% by mass of a conductive agent, 1.5% by mass of CMC (viscosity of 13000mPa.s) and 1.4% by mass of SBR (elastic modulus of 15MPa) in deionized water to prepare a negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector 3 to form a bottom layer 1, and then coating the negative electrode slurry A on the bottom layer 1 to form a top layer 2;
s3: and drying the negative current collector 3 coated with the negative electrode slurry A and the negative electrode slurry B to remove deionized water, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
And (3) matching and winding the negative electrode and the positive electrode → packaging → baking liquid injection → formation → secondary sealing → sorting to obtain the lithium ion battery, wherein the rolling, slitting, sheet making, winding, packaging, baking liquid injection, formation, secondary sealing and sorting are carried out by adopting conventional technical means in the field.
The specific preparation methods of the negative electrode slurry a and the negative electrode slurry B are the same as those in example 1.
Example 3
The negative electrode of the lithium ion battery comprises a negative electrode current collector 3 and a negative electrode coating, wherein the negative electrode coating comprises a bottom layer 1 and a top layer 2, the bottom layer 1 is coated on two surfaces of the negative electrode current collector 3, the coating thickness of a single-layer bottom layer 1 is 50 micrometers, the top layer 2 is coated on the bottom layer 1, and the coating thickness of the single-layer top layer 2 is 50 micrometers; the bottom layer 1 comprises 96.1% by mass of a negative electrode active material II (a silicon-carbon negative electrode material or a silicon-oxygen/carbon negative electrode material or a lithium-supplement silicon-carbon negative electrode material, SO2 g of capacity 430mAh/g), 1.0% of a conductive agent, 1.5% of sodium carboxymethylcellulose CMC (viscosity 10000mPa.s) and 1.4% of styrene butadiene rubber SBR (elastic modulus 10MPa), and the top layer 2 comprises a mixture I, wherein the mixture I comprises 96.1% by mass of a negative electrode active material I (a silicon-carbon negative electrode material or a silicon-oxygen/carbon negative electrode material or a lithium-supplement silicon-carbon negative electrode material), 1.7% of a conductive agent, 1.1% of sodium carboxymethylcellulose CMC (viscosity 20000mPa.s) and 1.1% of styrene butadiene rubber SBR (elastic modulus 40 MPa); the negative electrode active material I and the negative electrode active material II are the same in composition.
Further, the top layer 2 also comprises ethylene carbonate, and the ethylene carbonate accounts for 0.4% of the mixture I by mass.
The preparation method of the lithium ion battery cathode comprises the following steps:
s1: uniformly dispersing a mixture I consisting of 96.1 mass percent of a negative electrode active material I, 1.7 mass percent of a conductive agent, 1.1 mass percent of CMC (viscosity is 20000mPa.s) and 1.1 mass percent of SBR (elastic modulus is 40MPa) and 0.4 mass percent of ethylene carbonate accounting for the mixture I in deionized water to prepare negative electrode slurry A; uniformly dispersing 96.1% by mass of a negative electrode active material II, 1.0% by mass of a conductive agent, 1.5% by mass of CMC (viscosity: 10000mPa.s) and 1.4% by mass of SBR (elastic modulus: 10MPa) in deionized water to prepare a negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector 3 to form a bottom layer 1, and then coating the negative electrode slurry A on the bottom layer 1 to form a top layer 2;
s3: and drying the negative current collector 3 coated with the negative electrode slurry A and the negative electrode slurry B to remove deionized water, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
And (3) matching and winding the negative electrode and the positive electrode → packaging → baking liquid injection → formation → secondary sealing → sorting to obtain the lithium ion battery, wherein the rolling, slitting, sheet making, winding, packaging, baking liquid injection, formation, secondary sealing and sorting are carried out by adopting conventional technical means in the field.
The specific preparation method of the negative electrode slurry A comprises the following steps:
step 1: uniformly mixing and dispersing 30% of the total mass of the CMC (with the viscosity of 20000mPa.s) and all the conductive agents into deionized water;
step 2: then adding 25% of the total mass of the negative electrode active material I and 30% of the total mass of the CMC (the viscosity is 20000mPa.s), and uniformly dispersing;
and step 3: adding 25% of the total mass of the negative active material I and 40% of the total mass of the CMC (the viscosity is 20000mPa.s), and uniformly dispersing;
and 4, step 4: adding 25% of the total mass of the negative active material I, and uniformly dispersing;
and 5: adding 25% of the total mass of the negative active material I, and uniformly dispersing;
step 6: and finally, completely adding the SBR (with the elastic modulus of 40MPa), uniformly dispersing, adding the EC, and uniformly dispersing to obtain the negative electrode slurry A.
The specific preparation method of the negative electrode slurry B comprises the following steps:
step 1: uniformly mixing and dispersing 30% of the total mass of the CMC (with the viscosity of 10000mPa.s) and all the conductive agents into deionized water;
step 2: then adding 25% of the total mass of the negative electrode active material II and 30% of the total mass of the CMC (with the viscosity of 10000mPa.s), and uniformly dispersing;
and step 3: adding 25% of the total mass of the negative electrode active material II and 40% of the total mass of the CMC (with the viscosity of 10000mPa.s), and uniformly dispersing;
and 4, step 4: adding 25% of the total mass of the negative electrode active material II, and uniformly dispersing;
and 5: adding 25% of the total mass of the negative electrode active material II, and uniformly dispersing;
step 6: and finally, completely adding the SBR (with the elastic modulus of 10MPa) and uniformly dispersing to obtain the negative electrode slurry B.
Comparative example
The utility model provides a lithium ion battery negative pole, includes negative pole mass flow body 3 and negative coating, the negative coating includes long coating cream layer and short coating cream layer, long coating cream layer and short coating cream layer coat respectively on two surfaces of negative pole mass flow body, the coating thickness of long coating cream layer and the coating thickness of short coating cream layer are 110 mu m, long coating cream layer and short coating cream layer all include by the mass percent respectively be 96.1% negative pole active material II (silicon carbon negative pole material or silica/carbon negative pole material or mend lithium silicon carbon negative pole material, gram capacity 430mAh/g), 1.0% conductive agent, 1.5% sodium carboxymethylcellulose CMC (viscosity is 10000mPa.s) and 1.4% SBR (elastic modulus is 10MPa) constitute.
The preparation method of the lithium ion battery cathode comprises the following steps:
uniformly dispersing 96.1% of negative active material II, 1.0% of conductive agent, 1.5% of CMC (viscosity is 10000mPa.s) and 1.4% of SBR (elastic modulus is 10MPa) in deionized water to prepare negative slurry B, simultaneously coating the surfaces of two sides of a negative current collector 3 with the negative slurry B to form a long paste coating and a short paste coating, drying to remove the deionized water, rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
And (3) matching and winding the negative electrode and the positive electrode → packaging → baking liquid injection → formation → secondary sealing → sorting to obtain the lithium ion battery, wherein the rolling, slitting, sheet making, winding, packaging, baking liquid injection, formation, secondary sealing and sorting are carried out by adopting conventional technical means in the field.
The specific preparation method of the negative electrode slurry B comprises the following steps:
step 1: uniformly mixing 10% of the total mass of the CMC (with the viscosity of 10000mPa.s) and all the conductive agents, and dispersing the mixture into deionized water;
step 2: then adding 20% of the total mass of the negative electrode active material II and 30% of the total mass of the CMC (with the viscosity of 10000mPa.s), and uniformly dispersing;
and step 3: adding 30% of the total mass of the negative electrode active material II and 60% of the total mass of the CMC (with the viscosity of 10000mPa.s), and uniformly dispersing;
and 4, step 4: adding 30% of the total mass of the negative electrode active material II, and uniformly dispersing;
and 5: adding 20% of the total mass of the negative electrode active material II, and uniformly dispersing;
step 6: and finally, completely adding the SBR (with the elastic modulus of 10MPa) and uniformly dispersing to obtain the negative electrode slurry B.
Figure BDA0002429820330000101

Claims (8)

1. A lithium ion battery negative electrode comprises a negative electrode current collector (3) and a negative electrode coating, and is characterized in that: the negative coating comprises a bottom layer (1) and a top layer (2), the bottom layer (1) is coated on two surfaces of a negative current collector (3), the top layer (2) is coated on the bottom layer (1), the top layer (2) comprises a negative active material I, a conductive agent, a thickening agent I, a dispersing agent I and a binder I, the bottom layer (1) comprises a negative active material II, a conductive agent, a thickening agent II, a dispersing agent II and a binder II, the viscosity of the thickening agent I is greater than that of the thickening agent II, the viscosity of the dispersing agent I is greater than that of the dispersing agent II, and the elastic modulus of the binder I is greater than that of the binder II.
2. The lithium ion battery negative electrode of claim 1, wherein: the thickening agent I and the thickening agent II are the same substance, the dispersing agent I and the dispersing agent II are the same substance, and the binder I and the binder II are the same substance.
3. The lithium ion battery negative electrode of claim 1, wherein: the gram capacity of the negative electrode active material I is smaller than that of the negative electrode active material II.
4. The lithium ion battery negative electrode according to claim 1 or 3, characterized in that: the negative electrode active material I and the negative electrode active material II are both silicon-carbon negative electrode active materials.
5. The lithium ion battery negative electrode of claim 1, wherein: the top layer (2) also comprises ethylene carbonate.
6. The lithium ion battery negative electrode of claim 1, wherein: the thickness of the bottom layer (1) on any side surface of the negative current collector (3) is 37.5-60 mu m, and the thickness of the top layer (2) is 37.5-60 mu m.
7. The preparation method of the lithium ion battery cathode as claimed in any one of claims 1 to 6, characterized by comprising the following steps:
s1: uniformly dispersing a negative electrode active material I, a conductive agent, a thickening agent I, a dispersing agent I and a binder I in a solvent to prepare negative electrode slurry A, and uniformly dispersing a negative electrode active material II, a conductive agent, a thickening agent II, a dispersing agent II and a binder II in a solvent to prepare negative electrode slurry B;
s2: coating the negative electrode slurry B on two surfaces of a negative electrode current collector (3) to form a bottom layer (1), and then coating the negative electrode slurry A on the bottom layer (1) to form a top layer (2); or coating the negative electrode slurry B and the negative electrode slurry A on one side of the negative electrode current collector (3) at the same time, and then coating the negative electrode slurry B and the negative electrode slurry A on the other side of the negative electrode current collector (3) at the same time, wherein the negative electrode slurry B is coated on the negative electrode current collector (3) to form a bottom layer (1), and the negative electrode slurry A is coated on the negative electrode slurry B to form a top layer (2);
s3: and drying the negative current collector (3) coated with the negative slurry A and the negative slurry B to remove the solvent, and rolling, slitting and tabletting to obtain the lithium ion battery negative electrode.
8. The method for preparing the negative electrode of the lithium ion battery according to claim 7, wherein the method comprises the following steps: in S1, ethylene carbonate is further added to the negative electrode slurry a.
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