CN114805823A - Crosslinked composite binder, preparation method thereof, pole piece and secondary battery - Google Patents
Crosslinked composite binder, preparation method thereof, pole piece and secondary battery Download PDFInfo
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- CN114805823A CN114805823A CN202210438184.4A CN202210438184A CN114805823A CN 114805823 A CN114805823 A CN 114805823A CN 202210438184 A CN202210438184 A CN 202210438184A CN 114805823 A CN114805823 A CN 114805823A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
- C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
- C08G81/024—Block or graft polymers containing sequences of polymers of C08C or C08F and of polymers of C08G
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a cross-linked composite binder, a preparation method thereof, a pole piece and a secondary battery, wherein the structural formula of the cross-linked composite binder is shown as the following formula I; wherein a, b, c, d and e are all positive integers greater than or equal to 2. The crosslinking composite binder disclosed by the invention has super-strong adhesive force and film forming capability, can be firmly bonded with active substances, has a good stable chemical structure, can be balanced and continuously used under high voltage, does not generate delamination and peeling phenomena, and also has good electronic transmission capability and ion transmission capability, so that the transmission between the active substances is improved.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a cross-linked composite binder, a preparation method thereof, a pole piece and a secondary battery.
Background
The requirements of consumer-grade lithium ion battery products, particularly 5G mobile phones and the like on the endurance time and the volume of the lithium ion battery are continuously improved, and the energy density of the battery volume is urgently required to be further improved. Increasing the charging voltage of a lithium cobaltate battery can increase the volumetric energy density of the battery.
However, in the case of high voltage operation, oxygen is released due to high O atom activity in the positive electrode material, and the capacity of the lithium battery is rapidly decreased due to problems such as unstable positive electrode material-electrolyte interface (CEI), oxidative decomposition of the electrolyte solution, and elution of the transition metal, and thus the demand for practical production cannot be satisfied. One of the most effective ways to improve the performance of high voltage lithium batteries is to develop new high voltage binders. Polyvinylidene fluoride (PVDF) is a binder which is most widely applied to lithium ion battery systems at present, has good electrochemical stability, strong mechanical property and electrolyte absorption rate, but does not have lithium ion transmission capacity. And the PVDF and the active substance only exert the bonding effect through weak van der waals force, but weak van der waals force cannot provide enough bonding strength, so that the pole piece is easy to delaminate and peel under high-voltage operation, and the use requirement of the high-voltage electrode material cannot be met.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the cross-linked composite binder has good stable chemical structure, adhesive force, film forming capability and transmission capability.
In order to achieve the purpose, the invention adopts the following technical scheme:
a crosslinked composite binder having the formula I:
wherein a, b, c, d and e are all positive integers greater than or equal to 2.
The second purpose of the invention is: aiming at the defects of the prior art, the preparation method of the crosslinking composite binder is provided, and has the advantages of simple operation, good controllability and lower cost.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a cross-linked composite binder comprises the following steps:
step S1, mixing dopamine powder with Tris hydrochloric acid, and stirring under a shading condition to obtain a polydopamine solution;
step S2, mixing and stirring polyacrylic acid powder and a solvent, adding a lithium source, and reacting to obtain a polyacrylic acid-lithium polyacrylate solution;
and step S3, mixing and stirring the polydopamine solution and the polyacrylic acid-lithium polyacrylate solution to obtain the cross-linked composite binder.
Preferably, the weight part ratio of the dopamine powder to the Tris hydrochloric acid in the step S1 is 5-15: 0.01-0.5.
Preferably, the stirring time in the step S1 is 10-20 h.
Preferably, in the step S2, the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source is 1-10: 150-300: 0.1 to 1.
Preferably, the stirring time in the step S2 is 10-20 h.
Preferably, the weight part ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 1-5: 1-5.
Preferably, the lithium source is one or more of lithium hydroxide, lithium chloride, lithium carbonate or lithium bicarbonate.
The third purpose of the invention is that: aiming at the defects of the prior art, the pole piece is provided, and has good cycle stability and high-rate charge and discharge performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a pole piece comprises a current collector and an active substance layer arranged on at least one surface of the current collector, wherein the active substance layer comprises the cross-linked composite binder.
The fourth purpose of the invention is that: aiming at the defects of the prior art, the secondary battery is provided, and has good stability and electrochemical performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the pole piece.
Compared with the prior art, the invention has the beneficial effects that: the crosslinking composite binder disclosed by the invention has super-strong adhesive force and film forming capability, can be firmly bonded with active substances, has a good stable chemical structure, can be balanced and continuously used under high voltage, does not generate delamination and peeling phenomena, and also has good electronic transmission capability and ion transmission capability, so that the transmission between the active substances is improved.
Detailed Description
1. A crosslinked composite binder having the formula I:
wherein a, b, c, d and e are all positive integers greater than or equal to 2.
The cross-linked composite binder disclosed by the invention has acrylic acid-lithium polyacrylate groups, can be tightly connected with an electrode material, uniformly wraps the electrode material, improves the electron transmission capability and the ion transmission capability among active substances, and improves the long-cycle stability and the high-rate charge and discharge performance of an electrode; the crosslinking composite binder disclosed by the invention has polydopamine groups, has super-strong adhesive force and film forming capability, and can effectively remove precipitated oxygen, so that the growth of an anode electrolyte interface can be weakened, the release of oxygen can be reduced, and the phase change of the surface can be obviously inhibited; the crosslinking composite binder disclosed by the invention has a crosslinking system, and can form a network coating effect, so that the impedance of a material is effectively reduced, the electrochemical dynamics is improved, the system strength is enhanced, and the capacity retention rate and the stability are improved.
The traditional polyvinylidene fluoride (PVDF) is a binder which is most widely applied to a lithium ion battery system, has good electrochemical stability, strong mechanical property and electrolyte absorption rate, but does not have lithium ion transmission capability and needs toxic N-methyl pyrrolidone (NMP) as a solvent, so that serious environmental pollution exists. The crosslinking composite binder disclosed by the invention has super-strong adhesive force and film forming capability, can be firmly bonded with active substances, has a good stable chemical structure, can be balanced and continuously used under high voltage, does not generate delamination and peeling phenomena, and also has good electronic transmission capability and ion transmission capability, so that the transmission between the active substances is improved.
2. The preparation method of the crosslinking composite binder has the advantages of simple operation, good controllability and lower cost.
A preparation method of a cross-linked composite binder comprises the following steps:
step S1, mixing dopamine powder with Tris hydrochloric acid, and stirring under a shading condition to obtain a polydopamine solution;
step S2, mixing and stirring polyacrylic acid powder and a solvent, adding a lithium source, and reacting to obtain a polyacrylic acid-lithium polyacrylate solution;
and step S3, mixing and stirring the polydopamine solution and the polyacrylic acid-lithium polyacrylate solution to obtain the cross-linked composite binder.
The preparation method of the cross-linked composite binder is simple to operate and low in cost, effectively solves the problems of stability and electrical property of the anode material, and prolongs the service life of the battery.
Preferably, the weight part ratio of the dopamine powder to the Tris hydrochloric acid in the step S1 is 5-15: 0.01-0.5. The dopamine powder is subjected to self-polymerization in Tris hydrochloric acid to form a polydopamine solution so as to facilitate subsequent reaction, and the reaction formula is as follows. The generated polydopamine solution is easy to generate side reaction, discolor and influence judgment under the air or illumination condition, so that when dopamine powder is mixed with Tris hydrochloric acid, the mixture needs to be carried out under the condition of shading, and stirring needs to be carried out overnight during mixing, a certain stirring time is ensured, the polymerization process is fully reacted until the mixed solution becomes brownish black, and the uniform polydopamine solution is synthesized.
The stirring speed is not generally specified.
Preferably, the stirring time in the step S1 is 10-20 h. The stirring time in step S1 may be 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20 h. Preferably, the stirring time is 12-18 h.
Preferably, in the step S2, the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source is 1-10: 150-300: 0.1 to 1. Dissolving white polyacrylic acid powder in a solvent, stirring and filtering to ensure that the polyacrylic acid powder is fully dissolved in the solvent, and then adding a lithium source to form a gelatinous uniformly mixed polyacrylic acid-lithium polyacrylate solution. The stirring speed is not generally specified.
Preferably, the stirring time in the step S2 is 10-20 h. The stirring time in the step S2 is 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h and 20 h. Preferably, the stirring time is 12-18 h.
Preferably, the weight part ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 1-5: 1-5.
Preferably, the lithium source is one or more of lithium hydroxide, lithium chloride, lithium carbonate or lithium bicarbonate. Preferably, the lithium source is lithium hydroxide.
3. A pole piece has good circulation stability and high-rate charge-discharge performance.
A pole piece comprises a current collector and an active substance layer arranged on at least one surface of the current collector, wherein the active substance layer comprises the cross-linked composite binder. The pole piece can be a positive pole piece or a negative pole piece. When the current collector is a positive plate, the current collector is a copper foil, and when the current collector is a negative plate, the current collector is an aluminum foil. The active material layer comprises lithium cobaltate, the cross-linked composite binder and a conductive agent. And mixing lithium cobaltate, the cross-linked composite binder and conductive agent superconducting carbon (Super-P) according to the weight part ratio of 97:1.5:1.5 to prepare the positive plate.
4. A secondary battery having good stability and electrochemical properties.
A secondary battery comprises the pole piece. The secondary battery comprises the positive plate, the diaphragm, the negative plate, electrolyte and the shell, wherein the shell is used for coating the positive plate, the diaphragm, the negative plate and the electrolyte.
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 positive plate is the positive 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 also be subjected to a modification treatment, and a method of modifying the positive electrode active material should be known to those skilled in the art, for example, may be usedThe positive electrode active material is modified by coating, doping, etc., and the material used in the modification treatment may be one or a combination of more of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, W, etc., but is not limited thereto. 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; also can be LiBF adopted in anti-overcharging 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 a cyclic carbonate 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
A preparation method of a cross-linked composite binder comprises the following steps:
(1) preparation of Polydopamine (PDA):
7.0g of dopamine powder and 0.1353g of 100ml of Tris hydrochloric acid are mixed, and stirred overnight under the shading condition until the mixed solution becomes brownish black, so that a uniform polydopamine solution is synthesized.
The reaction equation is as follows: in the following reaction formula, n is a positive integer of 2 or more.
(2) Preparation of polyacrylic acid-lithium polyacrylate (PAA-PAALi):
5.0g polyacrylic acid powder was mixed with 200g 200ml deionized water, stirred overnight until all white powder was dissolved uniformly, and 0.6g LiOH was added to form a gel-like uniformly mixed polyacrylic acid-lithium polyacrylate solution.
The reaction equation is as follows: in the following reaction formula, m, f and c are positive integers greater than or equal to 2.
(3) Preparation of crosslinked composite binder
Mixing a polydopamine solution and a polyacrylic acid-lithium polyacrylate solution according to the weight ratio of polydopamine: polyacrylic acid is uniformly mixed according to the proportion of 1:1, and is stirred overnight to form a gelatinous mixed polydopamine-polyacrylic acid-lithium polyacrylate solution, namely a solution containing a crosslinking composite binder.
The reaction equation is as follows: a. b, c, d and e are all positive integers greater than or equal to 2.
Secondly, preparing the positive plate:
lithium cobaltate, conductive agent superconducting carbon (Super-P), and the cross-linked composite binder in a 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.
Thirdly, preparing the negative plate:
graphite, conductive agent superconducting carbon (Super-P), thickening agent carboxymethyl cellulose sodium (CMC) and binder Styrene Butadiene Rubber (SBR) are mixed according to a mass ratio of 96: 2.0: 1.0: 1.0, preparing slurry, coating the slurry on a current collector copper foil, drying at 85 ℃, cutting edges, cutting pieces, dividing strips, drying for 4 hours at 110 ℃ under a vacuum condition after dividing the strips, and welding lugs to prepare the lithium ion battery negative plate.
Fourthly, preparing 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.
Fifthly, preparing the lithium ion battery:
winding the positive plate, the diaphragm and the negative plate into a battery cell, wherein the oily 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: the weight part ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 1: 1.5.
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from example 1 is that: the weight part ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 1: 2.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from example 1 is that: the weight part ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 2: 1.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from example 2 is that: in the step S1, the weight part ratio of the dopamine powder to the Tris hydrochloric acid is 7: 0.4.
The rest is the same as embodiment 2, and the description is omitted here.
Example 6
The difference from example 2 is that: in the step S1, the weight part ratio of the dopamine powder to the Tris hydrochloric acid is 7: 0.01.
The rest is the same as embodiment 2, and the description is omitted here.
Example 7
The difference from example 2 is that: in the step S1, the weight part ratio of the dopamine powder to the Tris hydrochloric acid is 14: 0.1353.
The rest is the same as embodiment 2, and the description is omitted here.
Example 8
The difference from example 2 is that: in the step S2, the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source is 5:200: 0.6.
The rest is the same as embodiment 2, and the description is omitted here.
Example 9
The difference from example 2 is that: in the step S2, the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source is 10:200: 0.6.
The rest is the same as embodiment 2, and the description is omitted here.
Example 10
The difference from example 2 is that: in the step S2, the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source is 2:200: 0.6.
The rest is the same as embodiment 2, and the description is omitted here.
Comparative example 1
The difference from example 2 is that: the binder in the positive plate is PVDF binder.
The rest is the same as embodiment 2, and the description is omitted here.
And (3) performance testing: the secondary batteries prepared in the above examples 1 to 10 and comparative example 1 were subjected to an electrical property test under a charge-discharge condition of 2.0C and a charge-discharge range of 3.0V to 4.55V. The results of testing electrical properties are given in table 1 below.
TABLE 1
As can be seen from table 1 above, the crosslinked composite binder of the present invention has better electrical properties when applied to a secondary battery. The data of examples 1-10 and comparative example 1 show that the cross-linked composite binder shows higher capacity retention rate and no deterioration of the first charge-discharge efficiency; the cross-linked composite binder effectively improves the cycle stability and the charge and discharge performance. The cross-linked composite binder disclosed by the invention has acrylic acid-lithium polyacrylate groups, can be tightly connected with an electrode material, uniformly wraps the electrode material, improves the electron transmission capability and the ion transmission capability among active substances, and improves the long-cycle stability and the high-rate charge and discharge performance of an electrode; the crosslinking composite binder disclosed by the invention has polydopamine groups, has super-strong adhesive force and film forming capability, and can effectively remove precipitated oxygen, so that the growth of an anode electrolyte interface can be weakened, the release of oxygen can be reduced, and the phase change of the surface can be obviously inhibited; the cross-linked composite binder provided by the invention has a cross-linked system, and can form a network coating effect, so that the impedance of the material is effectively reduced, the electrochemical dynamics is improved, the strength of the system is enhanced, and the capacity retention rate and the stability are improved.
As can be seen from comparison of examples 1 to 4, when the weight ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in step S3 is set to 1:1.5, the prepared crosslinked composite binder has better performance when applied to a secondary battery. And a certain amount of polydopamine solution and polyacrylic acid-lithium polyacrylate solution are controlled to enable the reaction to be more uniform.
As a result of comparison between examples 2 and 5-7, when the weight ratio of dopamine powder to Tris hydrochloride in step S1 is set to 7:0.1353, the prepared cross-linked composite binder performs better when applied to a secondary battery. The proper Tris hydrochloric acid is helpful for dopamine to carry out self-polymerization reaction to generate uniformly mixed polydopamine.
As can be seen from comparison of examples 2 and 8 to 10, when the weight part ratio of the polyacrylic acid powder, the solvent and the lithium source in step S2 is set to 5:200:0.6, the prepared cross-linked composite binder performs better when applied to a secondary battery. Polyacrylic acid with proper concentration reacts with the lithium source more uniformly, and the effect is better.
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 improvement, replacement or modification made by those skilled in the art based on the present invention is 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. A crosslinked composite binder having the structural formula I:
wherein a, b, c, d and e are all positive integers greater than or equal to 2.
2. A preparation method of a cross-linked composite binder is characterized by comprising the following steps:
step S1, mixing dopamine powder with Tris hydrochloric acid, and stirring under a shading condition to obtain a polydopamine solution;
step S2, mixing and stirring polyacrylic acid powder and a solvent, adding a lithium source, and reacting to obtain a polyacrylic acid-lithium polyacrylate solution;
and step S3, mixing and stirring the polydopamine solution and the polyacrylic acid-lithium polyacrylate solution to obtain the cross-linked composite binder.
3. The method for preparing a cross-linked composite binder according to claim 2, wherein the weight ratio of dopamine powder to Tris hydrochloride in step S1 is 5-15: 0.01-0.5.
4. The preparation method of the crosslinked composite binder according to claim 3, wherein the stirring time in the step S1 is 10-20 h.
5. The preparation method of the crosslinked composite binder according to claim 2 or 4, wherein the weight ratio of the polyacrylic acid powder, the solvent and the lithium source in the step S2 is 1-10: 150-300: 0.1 to 1.
6. The preparation method of the crosslinked composite binder according to claim 5, wherein the stirring time in the step S2 is 10-20 h.
7. The method for preparing the crosslinked composite binder according to claim 6, wherein the weight ratio of the polydopamine solution to the polyacrylic acid-lithium polyacrylate solution in the step S3 is 1-5: 1-5.
8. The method of claim 2, wherein the lithium source is one or more of lithium hydroxide, lithium chloride, lithium carbonate, or lithium bicarbonate.
9. A pole piece, comprising a current collector, and an active material layer disposed on at least one surface of the current collector, wherein the active material layer comprises the crosslinked composite binder of claim 1.
10. A secondary battery comprising the pole piece of claim 10.
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