CN115109192A - Modified adhesive and preparation method and application thereof - Google Patents

Modified adhesive and preparation method and application thereof Download PDF

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Publication number
CN115109192A
CN115109192A CN202210627585.4A CN202210627585A CN115109192A CN 115109192 A CN115109192 A CN 115109192A CN 202210627585 A CN202210627585 A CN 202210627585A CN 115109192 A CN115109192 A CN 115109192A
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negative electrode
modified binder
parts
weight
modified
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吴秋丽
张凯
马斌
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Huizhou Liwinon Energy Technology Co Ltd
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Huizhou Liwinon Energy Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F236/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds
    • C08F236/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds
    • C08F236/04—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated
    • C08F236/10—Copolymers of compounds having one or more unsaturated aliphatic radicals, at least one having two or more carbon-to-carbon double bonds the radical having only two carbon-to-carbon double bonds conjugated with vinyl-aromatic monomers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • 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
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of secondary batteries, and particularly relates to a modified adhesive as well as a preparation method and application thereof. The method comprises the following steps: step S1, mixing butadiene, styrene, acrylate, acrylonitrile and a first solvent, and stirring to obtain a first treatment solution; step S2, adding an activating agent and an accelerating agent into a second solvent, mixing, adding the first treatment solution, and stirring to obtain a second treatment solution; and step S3, dialyzing the second treatment solution to remove impurities, and freezing and solidifying to obtain the modified binder. The preparation method of the modified binder is simple in preparation and good in controllability, and the modified styrene butadiene rubber has good low-temperature performance and good cycle performance when applied to batteries.

Description

Modified adhesive and preparation method and application thereof
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a modified adhesive as well as a preparation method and application thereof.
Background
With the development of the lithium ion battery in the field of quick charge, higher requirements are also put forward on the lithium ion battery binder. When the battery is charged and discharged at a high rate, the cyclic expansion rapidly increases, and thus an adhesive having a high adhesiveness is required to maintain the structural state of the pole piece during the cycle. Currently, polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA) are commonly used as binders. But polyvinylidene fluoride has relatively weak bonding strength and is expensive, so that the polyvinylidene fluoride is not suitable for a graphite system under a large multiplying power. On the other hand, the organic solvent N-methyl-2-pyrrolidone (NMP) used is toxic and is not beneficial to industrial production and environmental protection. Sodium carboxymethyl cellulose (CMC) is a common binder and thickener for lithium ion battery negative electrode materials, but CMC is brittle and has low cohesiveness. The styrene butadiene rubber has good cohesiveness and is used in a fast-filling system, but the low-temperature performance is poor, and the requirement of a high-performance fast-filling system on low temperature cannot be met. Therefore, a solution to the above technical problem is needed.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the preparation method of the modified binder is provided, the preparation is simple, the controllability is good, and the modified styrene butadiene rubber has good low-temperature performance and good cycle performance when being applied to a battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
the preparation method of the modified binder is characterized by comprising the following steps:
step S1, mixing butadiene, styrene, acrylate, acrylonitrile and a first solvent, and stirring to obtain a first treatment solution;
step S2, adding an activating agent and an accelerating agent into a second solvent, mixing, adding the first treatment solution, and stirring to obtain a second treatment solution;
and step S3, dialyzing the second treatment solution to remove impurities, and freezing and solidifying to obtain the modified binder.
Preferably, in the step S1, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 60-80: 20-60: 5-20: 1 to 20.
Preferably, the weight part ratio of the activating agent, the accelerating agent and the first treatment liquid in the step S2 is 0.01-10: 0.02-15: 200-350.
Preferably, the activating agent is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and the accelerator is N-hydroxysuccinimide.
Preferably, the freezing temperature in the step S3 is-30 ℃ to-10 ℃, and the coagulation time is 20-30 hours.
The second purpose of the invention is: aiming at the defects of the prior art, the modified binder is provided, and has good low-temperature performance and good binder.
In order to achieve the purpose, the invention adopts the following technical scheme:
the modified binder is prepared by the preparation method of the modified binder.
The third purpose of the invention is that: aiming at the defects of the prior art, the negative electrode slurry is provided, and has good low-temperature performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the negative electrode slurry comprises a negative electrode active material, a conductive agent, a thickening agent, a third solvent and the modified binder.
Preferably, the negative electrode active material is 80-100 parts by weight, the conductive agent is 1-5 parts by weight, the thickening agent is 0.5-2 parts by weight, the modified binder is 1-10 parts by weight, and the third solvent is 100-300 parts by weight.
The fourth purpose of the invention is that: aiming at the defects of the prior art, the negative plate is provided, and has good low-temperature performance and cycle performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the negative plate comprises a negative current collector and a negative active layer coated on at least one surface of the negative current collector, wherein the negative active layer comprises the negative slurry.
The fifth purpose of the invention is that: in order to overcome the defects of the prior art, the secondary battery is provided, and has good low-temperature performance and cycle performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the negative plate.
Compared with the prior art, the invention has the beneficial effects that: the preparation method of the modified binder is simple in preparation and good in controllability, and the modified styrene butadiene rubber has good low-temperature performance and good cycle performance when applied to batteries.
Detailed Description
1. A preparation method of a modified binder comprises the following steps:
step S1, mixing butadiene, styrene, acrylate, acrylonitrile and a first solvent, and stirring to obtain a first treatment solution;
step S2, adding an activating agent and an accelerating agent into a second solvent, mixing, adding the first treatment solution, and stirring to obtain a second treatment solution;
and step S3, dialyzing the second treatment solution to remove impurities, and freezing and solidifying to obtain the modified binder.
According to the preparation method of the modified binder, butadiene and styrene are used for preparing butadiene styrene rubber in an improved mode, acrylate and acrylonitrile are matched for modification treatment, an activating agent and an accelerating agent are used for activating and assisting in reaction, the modified binder generated by the reaction is more stable in structure and has good low-temperature performance, and the modified binder obtained through dialysis impurity removal and freezing solidification is better in performance.
Preferably, in the step S1, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 60-80: 20-60: 5-20: 1 to 20. Preferably, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 60: 20: 6: 7. 65: 23: 7: 12. 67: 25: 13: 16. 68: 26: 16: 18. 76: 60: 9: 11. 75: 54: 16: 14.
preferably, the weight part ratio of the activating agent, the accelerating agent and the first treatment liquid in the step S2 is 0.01-10: 0.02-15: 200-350. The weight part ratio of the activating agent to the accelerating agent to the first treatment liquid is 0.01:0.2:200, 0.1:0.5:200, 0.3:0.8:200, 2:4:230, 1:0.5:300, 0.4:2:200 and 4:7: 300.
Preferably, the activating agent is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and the accelerator is N-hydroxysuccinimide.
Preferably, the freezing temperature in the step S3 is-30 ℃ to-10 ℃, and the coagulation time is 20-30 hours. Freezing temperature is-30 deg.C, -25 deg.C, -20 deg.C, -15 deg.C, -10 deg.C, -12 deg.C, solidifying for 20 hours, 21 hours, 23 hours, 24 hours, 26 hours, 28 hours, 30 hours.
2. A modified binder having good low temperature properties and good binder properties.
The modified binder is prepared by the preparation method of the modified binder.
3. A negative electrode slurry having good low temperature properties.
The negative electrode slurry comprises a negative electrode active material, a conductive agent, a thickening agent, a third solvent and the modified binder.
Preferably, the negative electrode active material is 80-100 parts by weight, the conductive agent is 1-5 parts by weight, the thickener is 0.5-2 parts by weight, the modified binder is 1-10 parts by weight, and the third solvent is 100-300 parts by weight. Preferably, the negative electrode active material is 80 parts, 90 parts, 92 parts, 98 parts, 99 parts or 100 parts by weight, the conductive agent is 1 part, 2 parts, 3 parts, 4 parts or 5 parts by weight, and the thickener is 0.5 part, 0.8 part, 1.2 parts, 1.5 parts, 1.8 parts or 2 parts by weight. The modified binder is 1 part, 3 parts, 4 parts, 5 parts and 10 parts by weight. The weight parts of the third solvent are 100 parts, 120 parts, 160 parts, 190 parts, 200 parts, 210 parts, 230 parts, 250 parts, 280 parts and 300 parts.
4. A negative electrode sheet has good low-temperature performance and cycle performance.
The negative plate comprises a negative current collector and a negative active layer coated on at least one surface of the negative current collector, wherein the negative active layer comprises the negative slurry.
5. A secondary battery having good low-temperature performance and cycle performance.
A secondary battery may be a lithium ion battery, a sodium ion battery, a magnesium ion battery, a calcium ion battery, a potassium ion battery, or the like. Preferably, the following secondary battery is exemplified by a lithium ion battery, which includes a positive plate, a negative plate, a separator, an electrolyte, and a case, wherein the separator separates the positive plate from the negative plate, and the case is used for mounting the positive plate, the negative plate, the separator, and the electrolyte. The negative plate is the negative plate.
The positive plate comprises a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector, the positive active material layer comprises a positive active material, and the positive active material can be a chemical formula including but not limited to Li a Ni x Co y M z O 2-b N b (wherein a is more than or equal to 0.95 and less than or equal to 1.2, x>0, y is more than or equal to 0, z is more than or equal to 0, and x + y + z is 1,0 is more than or equal to b and less than or equal to 1, M is selected from one or more of Mn and Al and N is selected from F, P, S), and the positive active material can also be selected from the group consisting of but not limited to LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiCoFSO 4 、CuS 2 、FeS 2 、MoS 2 、NiS、TiS 2 And the like. The positive electrode active material may be modified, and the method for modifying the positive electrode active material is known to those skilled in the art, and for example, the positive electrode active material may be modified by coating, doping, or the likeThe material used for the modification treatment may be a combination including, but not limited to, one or more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc. And the positive electrode current collector is generally a structure or a part for collecting current, and the positive electrode current collector may be any material suitable for being used as a positive electrode current collector of a lithium ion battery in the field, for example, the positive electrode current collector may include, but is not limited to, a metal foil and the like, and more specifically, may include, but is not limited to, an aluminum foil and the like.
The negative plate comprises a negative current collector and a negative active material layer arranged on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material, and the negative active material can be one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate or other metals capable of forming an alloy with lithium. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be one or more selected from simple substance silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy; the tin-based material can be one or more selected from simple substance tin, tin oxide compound and tin alloy. The negative electrode current collector is generally a structure or a part for collecting current, and the negative electrode current collector may be any material suitable for use as a negative electrode current collector of a lithium ion battery in the art, for example, the negative electrode current collector may include, but is not limited to, a metal foil, and the like, and more specifically, may include, but is not limited to, a copper foil, and the like.
The lithium ion battery also comprises electrolyte, and the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt may be LiPF used in a high-temperature electrolyte 6 And/or LiBOB; or LiBF used in low-temperature electrolyte 4 、LiBOB、LiPF 6 At least one of (a); or LiBF used in anti-overcharge electrolyte 4 、LiBOB、LiPF 6 At least one of, LiTFSI; may also be LiClO 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of (1). And the organic solvent may be cyclicCarbonates, including PC, EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, control of H in the electrolyte 2 At least one of additives of O and HF content, additives for improving low temperature performance, and multifunctional additives.
Preferably, the material of the shell is one of stainless steel and an aluminum plastic film. More preferably, the housing is an aluminum plastic film.
The present invention will be described in further detail with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.
Example 1
1. A preparation method of a modified binder comprises the following steps:
uniformly mixing raw materials according to the mass fraction ratio of 68 parts of butadiene, 22 parts of styrene, 8 parts of acrylic ester and 2 parts of acrylonitrile, dissolving the mixture in 200ml of deionized water, and performing magnetic stirring at a rotating speed of 300r/min to prepare a uniform solution to obtain a first treatment solution.
And (2) dissolving 0.25g of EDC and 0.35g of NHS in 15ml of deionized water, and adding the solution into the first treatment solution obtained in the step (1) after the solution is completely dissolved, wherein the activator, the accelerator and the first mixed solution are mixed according to the weight part ratio of 2:5:270, and magnetically stirring at room temperature at a rotation speed of 300r/min for 24h to obtain a viscous homogeneous solution, namely the second treatment solution.
And (3) dialyzing the second treatment liquid obtained in the step (2) by using deionized water to remove impurity ions in the solution. And then placing the mixture in a freezing layer of a refrigerator for freezing until the mixture is solidified, and then placing the mixture in a freeze dryer for vacuum freeze drying to obtain the modified binder.
And (4) dissolving the modified binder obtained in the step (3) in deionized water, and magnetically stirring for 8 hours at room temperature at 300r/min until the modified binder is completely dissolved to prepare the binder with the solid content of 40%.
2. A preparation method of a negative plate comprises the following steps:
mixing and stirring the negative active material, the conductive agent, the thickening agent, the third solvent and the modified binder according to the weight ratio of 85:3:1.5:120:6 to obtain negative slurry, coating the negative slurry on a copper foil, drying at 85 ℃, cutting edges, cutting pieces, dividing strips, drying at 110 ℃ for 4 hours under a vacuum condition, and welding tabs to obtain the negative plate.
3. Preparing a positive plate:
lithium cobaltate, conductive agent superconducting carbon (Super-P) and binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97: 1.5: 1.5, uniformly mixing to prepare lithium ion battery anode slurry with certain viscosity, coating the slurry on a current collector aluminum foil, drying at 85 ℃, and then carrying out cold pressing; then trimming, cutting into pieces, slitting, drying for 4 hours at 110 ℃ under the vacuum condition after slitting, and welding the tabs to prepare the lithium ion battery positive plate.
4. Preparing an electrolyte:
mixing lithium hexafluorophosphate (LiPF) 6 ) Dissolving the mixture in a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) (the mass ratio of the three is 1: 2: 1) to obtain the electrolyte with the concentration of 1 mol/L.
5. Preparing a lithium ion battery:
winding the positive plate, the diaphragm and the prepared negative plate into a battery cell, wherein the diaphragm is positioned between the positive plate and the negative plate, the positive electrode is led out by spot welding of an aluminum tab, and the negative electrode is led out by spot welding of a nickel tab; and then placing the battery core in an aluminum-plastic packaging bag, injecting the electrolyte, and carrying out processes such as packaging, formation, capacity and the like to prepare the lithium ion battery.
Example 2
The difference from example 1 is that: in the step S1, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 62: 28: 8: 2.
the rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from example 1 is that: in the step S1, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 60: 30: 8: 2.
the rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from example 1 is that: in the step S1, the weight ratio of butadiene, styrene, acrylate and acrylonitrile is 72: 18: 8: 2.
the rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from example 1 is that: in the step S1, the weight ratio of butadiene to styrene to acrylate to acrylonitrile is 68:22: 6: 4.
the rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from example 1 is that: in the step S1, the weight ratio of butadiene to styrene to acrylate to acrylonitrile is 68:22: 5: 5.
the rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from example 1 is that: in the step S2, the weight ratio of the activator to the accelerator to the first treatment liquid is 0.2:1.5: 210.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from example 1 is that: the weight part ratio of the activating agent, the accelerator and the first treatment liquid in the step S2 is 2.5:7: 230.
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from example 1 is that: in the step S2, the weight part ratio of the activator, the accelerator, and the first treatment liquid is 7:13: 320.
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from example 1 is that: the weight part ratio of the activating agent, the accelerator and the first treatment liquid in the step S2 is 7:14: 350.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
1. A preparation method of negative electrode slurry comprises the following steps:
(1) 73 parts by weight of butadiene and 27 parts by weight of styrene are uniformly mixed, dissolved in 200ml of deionized water and magnetically stirred at 300r/min to prepare a uniform solution.
(2) Dissolving 0.25g EDC and 0.35g NHS in 15ml deionized water, adding into the mixed solution obtained in (1) after completely dissolving, and magnetically stirring for 24h at the room temperature at 300r/min to obtain viscous homogeneous solution.
(3) And (3) dialyzing the viscous solution obtained in the step (2) by using deionized water to remove impurity ions in the solution. And then placing the mixture in a freezing layer of a refrigerator for freezing until the mixture is solidified, and then placing the mixture in a freeze dryer for vacuum freeze drying to obtain the modified binder.
(4) And (4) partially dissolving the modified binder obtained in the step (3) in deionized water, and magnetically stirring for 8 hours at room temperature at 300r/min until the modified binder is completely dissolved to prepare the binder with the solid content of 40%.
2. Preparation of a negative plate: the method comprises the following steps:
mixing and stirring the negative active material, the conductive agent, the thickening agent, the third solvent and the modified binder according to the weight ratio of 85:3:1.5:120:6 to obtain negative slurry, coating the negative slurry on a copper foil, drying at 85 ℃, cutting edges, cutting pieces, dividing strips, drying at 110 ℃ for 4 hours under a vacuum condition, and welding tabs to obtain the negative plate.
3. Preparing a positive plate:
lithium cobaltate, conductive agent superconducting carbon (Super-P) and binder polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 97: 1.5: 1.5, uniformly mixing to prepare lithium ion battery anode slurry with certain viscosity, coating the slurry on a current collector aluminum foil, drying at 85 ℃, and then carrying out cold pressing; then trimming, cutting into pieces, slitting, drying for 4 hours at 110 ℃ under the vacuum condition after slitting, and welding the tabs to prepare the lithium ion battery positive plate.
4. Preparing an electrolyte:
mixing lithium hexafluorophosphate (LiPF) 6 ) Dissolving the mixture in a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) (the mass ratio of the three is 1: 2: 1) to obtain the electrolyte with the concentration of 1 mol/L.
5. Preparing a lithium ion battery:
winding the positive plate, the diaphragm and the prepared negative plate into a battery cell, wherein the diaphragm is positioned between the positive plate and the negative plate, the positive electrode is led out by spot welding of an aluminum tab, and the negative electrode is led out by spot welding of a nickel tab; and then placing the battery core in an aluminum-plastic packaging bag, injecting the electrolyte, and carrying out processes such as packaging, formation, capacity and the like to prepare the lithium ion battery.
Comparative example 2
The difference from example 1 is that: the preparation method of the modified binder comprises the following steps: the acrylonitrile is not contained, and the weight part ratio of the butadiene to the styrene to the acrylate in the step S1 is 68:22: 8.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 3
The difference from example 1 is that: the preparation method of the modified binder comprises the following steps: the acrylic ester is not contained, and the weight part ratio of the butadiene, the styrene, the acrylic ester, the acrylonitrile and the first solvent in the step S1 is 68:22: 2.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 4
The difference from example 1 is that: in the step S2, no accelerator is used, and the weight ratio of the activator to the first mixed solution in the step S2 is 2: 270.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 5
The difference from example 1 is that: in step S2, no activator is used, and the weight ratio of the accelerator to the first mixed solution in step S2 is 5: 270.
The rest is the same as embodiment 1, and the description is omitted here.
And (3) performance testing: the secondary batteries prepared in the above examples 1 to 10 and comparative examples 1 to 5 were subjected to a low-temperature discharge test, an expansion ratio test, a wettability test and a capacity retention ratio test, and the test results are reported in tables 1 and 2.
TABLE 1
Figure BDA0003678398270000101
Figure BDA0003678398270000111
TABLE 2
Item Thickness expansion ratio (%) Wettability (%) Capacity retention (%)
Example 1 1.3 68 85
Example 2 3.4 61 82
Example 3 3.6 58 81
Example 4 3.4 59 82
Example 5 3.5 57 83
Example 6 3.4 58 82
Example 7 3.4 56 83
Example 8 3.6 58 82
Example 9 3.5 56 81
Example 10 3.4 56 80
Comparative example 1 3.5 56 82
Comparative example 2 3.6 58 81
Comparative example 3 3.5 57 82
Comparative example 4 3.6 56 82
Comparative example 5 2.8 55 46
Capacity retention rate test: charging the lithium ion secondary battery to 4.25V at a constant current of 1C at 25 ℃, then charging to 0.05C at a constant voltage of 4.25V, standing for 5min, and then discharging to 2.8V at a constant current of 1C, wherein the process is a charge-discharge cycle process, and the discharge capacity at this time is the discharge capacity of the first cycle. The lithium ion secondary battery was subjected to 400-cycle charge/discharge tests in accordance with the above-described method, and the discharge capacity per one cycle was recorded. The cycle capacity retention (%) was 400 cycles of discharge capacity/first cycle of discharge capacity × 100%.
Testing of battery thickness expansion rate: at 12 ℃, the lithium ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage until the current is 0.05C, and then discharged to 3.0V at a constant current of 1C, which is the first cycle. The lithium ion battery was cycled 200 times according to the above conditions. The thickness of the cell before and after cycling was tested with a height gauge. The thickness expansion ratio was calculated by the following formula: thickness expansion ratio [ (thickness after cycle-thickness before cycle)/thickness before cycle ] × 100%.
And (3) wettability testing: at room temperature, 1ml of electrolyte is dripped on the surface of the negative plate, the spreading condition of the electrolyte on the surface of the negative plate is tested, and the wettability is calculated by the following formula: the wet-out ratio was [ (1-open area) ] × 100%.
As can be seen from table 1 above, the secondary batteries prepared according to the present invention are significantly improved in low-temperature performance, expansion rate, wettability, and capacity retention rate, compared to the secondary batteries of comparative examples 1 to 5. From examples 1 to 6 and comparative examples 1 to 3, when the weight ratio of butadiene, styrene, acrylate and acrylonitrile in the step S1 is set to 68:22: 8:2, the prepared secondary battery has better low-temperature performance, because the acrylate can improve the wettability of the pole piece and the electrolyte and promote the low-temperature performance of the battery, the acrylonitrile monomer promotes the lithium ion transmission, so that the battery has excellent dynamic performance, and the two monomers can exert great advantages in cooperation with the low-temperature performance.
As shown by comparison of examples 1 and 7-10, when the weight part ratio of the activator, the accelerator and the first treatment liquid in step S2 is set to be 2:5:270, the prepared secondary battery has better low-temperature performance, the raw materials in the first mixed liquid react under the combined action of the activator and the accelerator, and the obtained adhesive property can improve the low-temperature performance and the cycle life of the battery core.
The comparison of the embodiment 1 and the comparative examples 1 to 3 shows that butadiene and styrene are used for preparing styrene butadiene rubber, acrylate and acrylonitrile are used for modification, the prepared modified adhesive can improve the wettability of a pole piece and electrolyte and promote the low-temperature performance of the battery, the acrylonitrile monomer promotes lithium ion transmission, so that the battery has excellent dynamic performance, and the two monomers have great advantages in cooperation with the low-temperature performance compared with the case that a single material is used for modification.
As can be seen from comparison of example 1 and comparative examples 4 to 5, when the weight part ratio of the activator, the accelerator and the first treatment liquid in step S2 is set to 2:5:270, the prepared modified binder has better performance. The activator activates the raw materials in the first mixed solution, and the accelerator accelerates the reaction of the activated components, so that when the amount of the activator is not proper, the reaction rate is influenced, and the performance of the modified binder is influenced. When the activator is not used, the reaction process is slow, and the product performance is greatly influenced.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious modifications, substitutions or alterations based on the present invention will fall within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (10)

1. The preparation method of the modified binder is characterized by comprising the following steps:
step S1, mixing butadiene, styrene, acrylate, acrylonitrile and a first solvent, and stirring to obtain a first treatment solution;
step S2, adding an activating agent and an accelerating agent into a second solvent, mixing, adding the first treatment liquid, and stirring to obtain a second treatment liquid;
and step S3, dialyzing the second treatment solution to remove impurities, and freezing and solidifying to obtain the modified binder.
2. The method for preparing the modified binder according to claim 1, wherein the weight ratio of butadiene, styrene, acrylate and acrylonitrile in the step S1 is 60-80: 20-60: 5-20: 1 to 20.
3. The method for preparing the modified binder according to claim 1 or 2, wherein the weight ratio of the activator, the accelerator and the first treatment liquid in step S2 is 0.01-10: 0.02-15: 200-350.
4. The method of claim 3, wherein the activator is 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride and the accelerator is N-hydroxysuccinimide.
5. The preparation method of the modified binder according to claim 1, wherein the freezing temperature in the step S3 is-30 ℃ to-10 ℃, and the modified binder is solidified for 20-30 hours.
6. A modified binder obtained by the method for producing a modified binder according to any one of claims 1 to 5.
7. A negative electrode slurry comprising a negative electrode active material, a conductive agent, a thickener, a third solvent, and the modified binder according to claim 6.
8. The negative electrode slurry according to claim 7, wherein the negative electrode active material is 80 to 100 parts by weight, the conductive agent is 1 to 5 parts by weight, the thickener is 0.5 to 2 parts by weight, the third solvent is 100 to 300 parts by weight, and the modified binder is 1 to 10 parts by weight.
9. A negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer coated on at least one surface of the negative electrode current collector, wherein the negative electrode active layer comprises the negative electrode slurry according to claim 7 or 8.
10. A secondary battery comprising the negative electrode sheet according to claim 9.
CN202210627585.4A 2022-06-06 2022-06-06 Modified adhesive and preparation method and application thereof Pending CN115109192A (en)

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Publication number Priority date Publication date Assignee Title
US20170155152A1 (en) * 2015-11-30 2017-06-01 Lg Chem, Ltd. Binder for secondary battery having improved properties and negative electrode for secondary battery comprising the same
CN110183584A (en) * 2019-05-05 2019-08-30 欣旺达惠州动力新能源有限公司 A kind of acrylonitrile polymer emulsion binder and preparation method thereof
CN113880999A (en) * 2021-10-14 2022-01-04 惠州亿纬锂能股份有限公司 Adhesive and preparation method and application thereof
CN114520398A (en) * 2022-02-28 2022-05-20 惠州锂威电子科技有限公司 Diaphragm, preparation method thereof and secondary battery

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Publication number Priority date Publication date Assignee Title
US20170155152A1 (en) * 2015-11-30 2017-06-01 Lg Chem, Ltd. Binder for secondary battery having improved properties and negative electrode for secondary battery comprising the same
CN110183584A (en) * 2019-05-05 2019-08-30 欣旺达惠州动力新能源有限公司 A kind of acrylonitrile polymer emulsion binder and preparation method thereof
CN113880999A (en) * 2021-10-14 2022-01-04 惠州亿纬锂能股份有限公司 Adhesive and preparation method and application thereof
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