CN108878886B - Thick battery pole piece and water-based composite binder thereof - Google Patents
Thick battery pole piece and water-based composite binder thereof Download PDFInfo
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- CN108878886B CN108878886B CN201810752383.6A CN201810752383A CN108878886B CN 108878886 B CN108878886 B CN 108878886B CN 201810752383 A CN201810752383 A CN 201810752383A CN 108878886 B CN108878886 B CN 108878886B
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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
- H01M4/623—Binders being polymers fluorinated 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention belongs to the technical field of batteries, and particularly relates to a water-based composite binder for a thick pole piece of a battery, which at least comprises the following components in parts by weight: 5-8 parts of vinyl fluoride polymer; 0.5-1 part by weight of a crosslinked water-absorbent polymer; 20-40 parts of water; the vinyl fluoride polymer and the crosslinked water-absorbent polymer form an entangled and interlaced polymer network. Compared with the prior art, the molecular chain of the crosslinked water-absorbing polymer is in a net structure, the interaction of the vinyl fluoride polymer and the crosslinked water-absorbing polymer enables the high molecular chain and the high molecular net structure to interact to form a polymer network which is mutually entangled and staggered, and the phenomenon that a binder is dissolved out can not occur even if the electrolyte is placed for a long time.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a battery thick pole piece and a water-based composite binder thereof.
Background
The lithium ion battery has the characteristics of high energy density, high working voltage, small self-discharge and the like, but because the organic electrolyte is used, and the solvent of the electrolyte is selected from an organic solvent (generally N-methylpyrrolidone (NMP)), the electrolyte is volatile, flammable and explosive, and has serious harm and pollution to human bodies and the environment, and potential safety hazards exist. Compared with organic systems, water-based batteries have the advantages of low cost and high safety. This is because the water-based battery uses water as a solvent, which is common, environmentally friendly, and inexpensive.
SBR or PTFE is often used as a binder in water-based batteries. However, the SBR has weak binding power, and thus, the active material of the battery is not firmly bound, and thus, the cycle stability of the battery is poor, which affects the lifespan of the battery. The PTFE emulsion and the PVDF solution can be used as aqueous binders, the binding power is good, but the PTFE emulsion has water solubility, so that PTFE can be dissolved out along with the increase of soaking time in an electrolyte and the progress of charge and discharge cycles, so that a pole piece is softened, materials fall off, the capacity is reduced, and the cycling stability of a battery is poor.
On the other hand, the battery pole piece added with PTFE and PVDF has lower surface energy, thereby causing the problem of poor pole piece wettability, increasing the internal resistance of the pole piece and reducing the ion transmission speed in the battery pole piece, further causing the problems of poor battery capacity performance, increased polarization and the like.
In addition, most of the existing preparation processes of the water-based battery slurry are slurry drawing processes, and the preparation processes are characterized in that the thickness of a pole piece is thin, the conductivity is excellent, the multiplying power performance is excellent, but a large amount of current collectors are used as supports, so that certain material waste is caused, the size of the pole piece is large, and thick electrodes are difficult to realize.
In view of the above, the invention aims to provide a water-based composite binder for a thick pole piece of a battery, which has the advantages of low cost, environmental protection, simple preparation method and the like.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the water-based composite binder for the thick pole piece of the battery has the advantages of low cost, environmental protection, simple preparation method and the like, and the water-based battery thick pole piece prepared by the binder can reduce the polarization of the pole piece, increase the mechanical stability of the pole piece and solve the problem of dissolution of the binder, thereby improving the cycling stability of the battery using the thick pole piece.
In order to achieve the purpose, the invention adopts the following technical scheme:
the water-based composite binder for the thick pole piece of the battery at least comprises the following components in parts by weight:
5-8 parts of vinyl fluoride polymer;
0.5-1 part by weight of a crosslinked water-absorbent polymer;
20-40 parts of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network.
The weight ratio of the vinyl fluoride polymer to the cross-linked water-absorbing polymer must be in the range, the prepared pole piece can not fall off and dissolve, the phenomenon of dissolving out of the binder does not occur in the placing process, and the charge-discharge cycle performance is excellent. When the value exceeds the range, the pole piece has the phenomena of large polarization, poor circulation stability and the like.
As an improvement of the water-based composite binder for the battery thick pole piece, the fluoroethylene polymer is PTFE and/or PVDF. The PTFE emulsion and the PVDF emulsion are high-molecular chain polymers, the bonding mechanism is that after the PTFE emulsion and the PVDF emulsion are fully mixed with powder (a conductive agent and an active substance), high-molecular chains of the PTFE emulsion and the PVDF emulsion can form a network structure to be intertwined with each other, so that the powder is intertwined with each other, the bonding effect is achieved, and if the PTFE emulsion and the PVDF solution are purely in physical and mechanical properties, the thick pole piece can be prevented from powder falling and has a smooth surface. However, because the thick pole piece is applied to aqueous electrolyte for charging and discharging, and because of the low surface energy of PTFE and PVDF, the pole piece prepared by the thick pole piece has low water retention rate and poor water wettability, and causes the problems of large polarization, unsatisfactory capacity exertion, poor cycle stability and the like in the charging and discharging process of the battery.
As an improvement of the water-based composite binder for the thick pole piece of the battery, the cross-linked water-absorbing polymer is at least one of cross-linked sodium carboxymethyl cellulose, cross-linked sodium polyacrylate and cross-linked polyvinylpyrrolidone. The invention adopts the crosslinked water-absorbing polymer (crosslinked sodium carboxymethylcellulose, crosslinked sodium polyacrylate and crosslinked polyvinylpyrrolidone) and the vinyl fluoride polymer as the adhesive of the water-based thick pole piece. On one hand, the cross-linked water-absorbing polymer has strong hydrophilicity and water retention because the molecular structure of the cross-linked water-absorbing polymer contains more hydrophilic functional groups, so that the water absorption and water retention of the thick pole piece can be increased, the polarization generated in the charging and discharging process is reduced, the problem of poor capacity exertion of the pole piece is solved, and the cycling stability of the pole piece is improved. On the other hand, the cross-linked water-absorbing polymer is a macromolecular net structure, the macromolecular chain of the vinyl fluoride polymer and the macromolecular net structure of the cross-linked water-absorbing polymer can be entangled and mixed through sufficient grinding and mixing, and the network structure of the binder is formed through interaction, so that the interaction among the binders is increased, the problem of binder dissolution of the thick pole piece placed in the aqueous electrolyte for a long time is solved, and the binding firmness of the active substance and the dry powder of the conductive agent is increased.
As an improvement of the water-based composite adhesive for the battery thick pole piece, the average molecular weight of the vinyl fluoride polymer is 60-80 ten thousand.
As an improvement of the water-based composite binder for the battery thick pole piece, the average molecular weight of the cross-linked sodium carboxymethyl cellulose is 60-80 ten thousand, the molecular weight of the cross-linked sodium polyacrylate is 300-700 ten thousand, and the average molecular weight of the cross-linked polyvinylpyrrolidone is 4-8 ten thousand. The above molecular weight is selected to satisfy product requirements based on viscosity and binding properties within this range and to exhibit excellent properties.
As an improvement of the water-based composite binder for the thick pole piece of the battery, the crosslinking degree of the crosslinked water-absorbing polymer is 60-85%, and the crosslinked water-absorbing polymer has certain swelling degree and certain binding property in the crosslinking range.
Compared with the prior art, the molecular chain of the crosslinked water-absorbing polymer is in a net structure, the interaction of the vinyl fluoride polymer and the crosslinked water-absorbing polymer enables the high molecular chain and the high molecular net structure to interact to form a polymer network which is mutually entangled and staggered, and the phenomenon that a binder is dissolved out can not occur even if the electrolyte is placed for a long time. Experiments show that the binder obtained by mixing the vinyl fluoride polymer and the non-crosslinked water-absorbing polymer (sodium carboxymethyl cellulose and polyvinylpyrrolidone) can dissolve out when the binder is placed in the electrolyte for a long time, probably because the acting force of mutual entanglement of two macromolecular chains is weak, and the two binders of the vinyl fluoride polymer and the non-crosslinked water-absorbing polymer have better dispersibility in water and can dissolve out when the binder is placed for a long time.
The invention also provides a battery thick pole piece, which comprises a current collector and an active substance layer coated on the surface of the current collector, wherein the active substance layer comprises an active substance, an adhesive and a conductive agent, and the adhesive is the adhesive disclosed by the invention. The pole piece comprises a positive pole piece and a negative pole piece, the positive pole active substance comprises at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate and nickel iron Prussian blue, and the negative pole active substance comprises at least one of hard carbon, soft carbon, natural graphite, artificial graphite, mesocarbon microbeads, silicon-carbon composites and the like. The conductive agent is at least one of superconducting carbon, graphene, carbon fiber and carbon nano tube. The positive current collector is aluminum foil, and the negative current collector is copper foil. As the separator, an aqueous separator (glass fiber separator, nonwoven wood separator) was used. The packaging mode of the battery is winding or lamination.
As an improvement of the battery thick pole piece, the preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for sufficient grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding an active substance, and performing sufficient grinding to enable the active substance, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a current collector, tabletting and drying to obtain the pole piece.
The invention compounds the common vinyl fluoride polymer and the crosslinked water-absorbing polymer (crosslinked sodium carboxymethylcellulose, crosslinked sodium polyacrylate and crosslinked polyvinylpyrrolidone), adopts the adhesive to prepare the pole piece by a semidry method, can keep excellent adhesive condition under less solvent, does not crack or fall powder, and can keep certain mechanical stability and does not soften in aqueous electrolyte. Through the mixed use of two binders of a high-molecular chain polymer (PTFE and PVDF) and a high-molecular net polymer (crosslinked water-absorbing polymer), a crosslinked polymer network can be formed, the mutual entanglement among the binders is increased, and the situations of binder dissolution and pole piece softening of a water-soluble binder in electrolyte for a long time are avoided. And the aqueous full battery prepared by adopting the thick positive and negative pole pieces has excellent capacity performance and cycling stability. In addition, the invention adopts a novel semi-dry method to prepare the water system battery thick sheet, can increase the effective active substance mass in the unit mass of the battery, and reduces the use and waste of the current collector.
As an improvement of the battery thick pole piece, the thickness of the active substance layer is 1mm-2 mm.
As an improvement of the battery thick pole piece, the weight ratio of the active substance, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is (75-85): (9.5-16): 5-8): 0.5-1.
Compared with the prior art, the pole piece has smooth surface, does not fall off powder, and does not have the phenomena of binder dissolution and cracking even if being immersed in the electrolyte for 3 months. The thick pole piece prepared by the semi-dry method has excellent capacity and cycling stability when being used for assembling a water system battery, and the pole piece still has excellent mechanical stability after cycling. The method also has the characteristics of low cost, environmental protection, simplicity and feasibility
Detailed Description
The technical solutions of the present invention are described below with specific examples, but the scope of the present invention is not limited thereto.
Example 1
The embodiment provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
6 parts by weight of a vinyl fluoride polymer;
0.6 part by weight of a crosslinked water-absorbent polymer;
30 parts of water;
the vinyl fluoride polymer and the crosslinked water-absorbent polymer form an entangled and interlaced polymer network.
The vinyl fluoride polymer is PTFE, the cross-linked water-absorbing polymer is cross-linked sodium carboxymethyl cellulose, the average molecular weight of the PTFE is 70 ten thousand, the average molecular weight of the cross-linked sodium carboxymethyl cellulose is 70 ten thousand, and the cross-linking degree of the cross-linked sodium carboxymethyl cellulose is 75%.
Example 2
The embodiment provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
7 parts by weight of a vinyl fluoride polymer;
0.9 part by weight of a crosslinked water-absorbent polymer;
35 parts by weight of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network.
The vinyl fluoride polymer is PVDF. The cross-linked water-absorbing polymer is cross-linked sodium polyacrylate.
The average molecular weight of the PVDF was 65 ten thousand. The molecular weight of the crosslinked sodium polyacrylate is 400 ten thousand, and the crosslinking degree of the crosslinked sodium polyacrylate is 80%.
Example 3
The embodiment provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
6.5 parts by weight of a vinyl fluoride polymer;
0.75 part by weight of a crosslinked water-absorbent polymer;
28 parts of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network.
The vinyl fluoride polymer is PVDF. The cross-linked water-absorbing polymer is cross-linked polyvinylpyrrolidone. The average molecular weight of the polyvinyl fluoride PVDF was 68 ten thousand. The average molecular weight of the crosslinked polyvinylpyrrolidone was 7 ten thousand. The degree of crosslinking of the crosslinked polyvinylpyrrolidone was 65%.
Example 4
The embodiment provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
7.5 parts by weight of a vinyl fluoride polymer;
0.85 part by weight of a crosslinked water-absorbent polymer;
33 parts of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network.
The fluoroethylene polymer is PTFE, the crosslinked water-absorbing polymer is a mixture of crosslinked sodium carboxymethylcellulose and crosslinked sodium polyacrylate, and the mass ratio of the crosslinked water-absorbing polymer to the crosslinked sodium carboxymethylcellulose to the crosslinked sodium polyacrylate is 1: 1. the average molecular weight of the vinyl fluoride polymer was 73 ten thousand. The average molecular weight of the croscarmellose sodium is 63 ten thousand, and the molecular weight of the crosslinked sodium polyacrylate is 600 ten thousand. The degree of crosslinking of croscarmellose sodium is 69% and the degree of crosslinking of sodium crospovidone is 62%.
Example 5
The embodiment provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
5.5 parts by weight of a vinyl fluoride polymer;
0.62 part by weight of a crosslinked water-absorbent polymer;
27 parts by weight of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network.
The vinyl fluoride polymer is PTFE. The cross-linked water-absorbing polymer is cross-linked sodium polyacrylate and cross-linked polyvinylpyrrolidone, and the mass ratio of the cross-linked water-absorbing polymer to the cross-linked polyvinylpyrrolidone is 1: 2. the average molecular weight of PTFE was 78 ten thousand. The molecular weight of the crosslinked sodium polyacrylate is 500 ten thousand, and the average molecular weight of the crosslinked polyvinylpyrrolidone is 6.5 ten thousand. The crosslinking degree of the crosslinked sodium polyacrylate is 82%, and the crosslinking degree of the crosslinked polyvinylpyrrolidone is 74%.
Comparative example 1
The comparative example provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
6 parts by weight of a vinyl fluoride polymer;
0.6 part by weight of a water-absorbent polymer;
30 parts of water;
the fluoroethylene polymer is PTFE, the water-absorbing polymer is sodium carboxymethyl cellulose, and the average molecular weight of the PTFE is 70 ten thousand.
Comparative example 2
The comparative example provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
7 parts by weight of a vinyl fluoride polymer;
0.9 part by weight of a water-absorbent polymer;
35 parts by weight of water;
the vinyl fluoride polymer is PVDF. The water-absorbing polymer is sodium polyacrylate. The average molecular weight of PVDF is 65 ten thousand.
Comparative example 3
The comparative example provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
6.5 parts by weight of a vinyl fluoride polymer;
0.75 part by weight of a water-absorbent polymer;
28 parts of water;
the vinyl fluoride polymer is PVDF. The water-absorbing polymer is polyvinylpyrrolidone. The average molecular weight of the polyvinyl fluoride PVDF was 68 ten thousand.
Comparative example 4
The comparative example provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
6 parts by weight of a vinyl fluoride polymer;
30 parts of water;
the vinyl fluoride polymer was PTFE, which has an average molecular weight of 70 ten thousand.
Comparative example 5
The comparative example provides a water-based composite binder for a thick battery pole piece, which at least comprises the following components in parts by weight:
0.62 part by weight of a crosslinked water-absorbent polymer;
27 parts by weight of water;
the cross-linked water-absorbing polymer is cross-linked sodium polyacrylate. The molecular weight of the crosslinked sodium polyacrylate is 500 ten thousand.
Example 6
The embodiment provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material lithium cobaltate, a binder and a conductive agent superconducting carbon, and the binder is the binder described in embodiment 1.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the cross-linked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the cross-linked water-absorbing polymer to form a uniform conductive network, then adding a positive active material lithium cobaltate, and fully grinding to enable the positive active material, the conductive agent and the cross-linked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto an aluminum foil of the positive current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.5mm, wherein the weight ratio of the positive active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 81:12.4:6: 0.6.
Example 7
The embodiment provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material lithium nickelate, a binder and a conductive agent carbon fiber, and the binder is the binder described in embodiment 2.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a positive active material lithium nickelate, and fully grinding to enable the positive active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network, thereby obtaining a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto an aluminum foil of the positive current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.3mm, wherein the weight ratio of the positive active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 79:13.1:7: 0.9.
Example 8
The embodiment provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material lithium manganate, a binder and a conductive agent graphene, and the binder is the binder described in embodiment 3.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a positive active material lithium manganate, and fully grinding to enable the positive active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network, thereby obtaining a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto an aluminum foil of the positive current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.8mm, wherein the weight ratio of the positive active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 82:10.75:6.5: 0.75.
Example 9
The embodiment provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material, namely nickel cobalt lithium manganate, a binder and a conductive agent, namely carbon nanotubes, and the binder is the binder described in embodiment 4.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a positive active material, namely nickel cobalt lithium manganate, and fully grinding to enable the positive active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network, thus obtaining a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto an aluminum foil of the positive current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.1mm, wherein the weight ratio of the positive active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 77:14.65:7.5: 0.85.
Example 10
The embodiment provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material, namely nickel-cobalt lithium aluminate, a binder and a conductive agent, namely carbon nano tubes, and the binder is the binder described in embodiment 5.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinking water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinking water-absorbing polymer to form a uniform conductive network, then adding a positive active substance of lithium nickel cobalt aluminate, and fully grinding to enable the positive active substance, the conductive agent and the crosslinking water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto an aluminum foil of the positive current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.1mm, wherein the weight ratio of the positive active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 82.5:11.38:5.5: 0.62.
Example 11
The embodiment provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material silicon carbon negative electrode, a binder and a conductive agent superconducting carbon, and the binder is the binder described in embodiment 1.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a negative active material, namely a silicon-carbon negative electrode, and fully grinding to enable the negative active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a copper foil of a negative current collector, tabletting and drying to obtain the pole piece. The thickness of the negative electrode active material layer in the pole piece is 1.6mm, wherein the weight ratio of the negative electrode active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 81:12.4:6: 0.6.
Example 12
The embodiment provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises negative active material mesocarbon microbeads, a binder and a conductive agent carbon fiber, and the binder is the binder described in embodiment 2.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding the negative active substance mesophase carbon microspheres, and fully grinding to enable the negative active substance, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a copper foil of a negative current collector, tabletting and drying to obtain the pole piece. The thickness of the negative electrode active material layer in the pole piece is 1.55mm, wherein the weight ratio of the negative electrode active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 79:13.1:7: 0.9.
Example 13
The embodiment provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material, namely hard carbon, a binder and a conductive agent, namely graphene, and the binder is the binder described in embodiment 3.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a negative active material, namely hard carbon, and fully grinding to enable the negative active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a copper foil of a negative current collector, tabletting and drying to obtain the pole piece. The thickness of the negative electrode active material layer in the pole piece is 1.25mm, wherein the weight ratio of the negative electrode active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 82:10.75:6.5: 0.75.
Example 14
The embodiment provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material, namely natural graphite, a binder and a conductive agent, namely superconducting carbon, and the binder is the binder described in embodiment 4.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding a negative active material, namely natural graphite, and fully grinding to enable the negative active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a copper foil of a negative current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.2mm, wherein the weight ratio of the negative active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 77:14.65:7.5: 0.85.
Example 15
The embodiment provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises negative active material artificial graphite, a binder and a conductive agent graphene, and the binder is the binder described in embodiment 5.
The preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for full grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding the negative active material artificial graphite, and fully grinding to enable the negative active material, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
and fourthly, transferring the semi-dry powder obtained in the third step onto a copper foil of a negative current collector, tabletting and drying to obtain the pole piece. The thickness of the positive active material layer in the pole piece is 1.4mm, wherein the weight ratio of the negative active material, the conductive agent, the vinyl fluoride polymer and the cross-linked water-absorbing polymer is 82.5:11.38:5.5: 0.62.
Comparative example 6
The comparative example provides a thick positive plate of a battery, which comprises a positive current collector and a positive active material layer coated on the surface of the positive current collector, wherein the positive active material layer comprises a positive active material lithium cobaltate, a binder and conductive agent superconducting carbon, and the binder is the binder in the comparative example 1. The thickness of the positive active material layer in the pole piece is 1.5mm, wherein the weight ratio of the positive active material, the conductive agent and the adhesive is 81:12.4: 6.6.
Comparative examples 7 to 10
Unlike comparative example 6, the adhesive was the adhesive of comparative examples 2 to 5, and the remainder was the same as in comparative example 6.
Comparative example 11
The comparative example provides a thick negative plate of a battery, which comprises a negative current collector and a negative active material layer coated on the surface of the negative current collector, wherein the negative active material layer comprises a negative active material silicon-carbon negative electrode, a binder and a conductive agent superconducting carbon, and the binder is the binder in the comparative example 1. The thickness of the negative electrode active material layer in the pole piece is 1.6mm, wherein the weight ratio of the negative electrode active material, the conductive agent and the adhesive is 81:12.4: 6.6.
Comparative examples 12 to 15
Unlike comparative example 11, the adhesive was the adhesive of comparative examples 2 to 5, and the remainder was the same as comparative example 11.
The pole pieces provided in examples 6 to 15 and comparative examples 6 to 15 were subjected to stability test in an aqueous electrolyte: the electrode sheets provided in examples 6 to 15 and comparative examples 6 to 15 were placed in an electrolyte at room temperature (25 ℃ C.) for 3 months to observe the phenomena, such as dissolution, dusting, softening, and dissolution of the binder, and the results are shown in Table 1.
Table 1: physical Properties of the Pole pieces provided in examples 6-15 and comparative examples 6-15
As can be seen from Table 1, the pole piece of the invention has high mechanical strength, no powder falling and smooth surface, and can still maintain good mechanical property, be undissolved and have no binder dissolution phenomenon when being placed in aqueous electrolyte for 3 months.
Capacity retention rate test: the positive electrode sheets of examples 6 to 10 and the negative electrode sheets of examples 11 to 15 were assembled at room temperature to obtain batteries, numbered from S1 to S5, and the positive electrode sheets of comparative examples 6 to 10 and the negative electrode sheets of comparative examples 11 to 15 were assembled to obtain batteries, numbered from D1 to D5, which were charged at a current of 0.1C to an upper limit cut-off voltage, then left for 10min, and then discharged at the same 0.1C to a lower limit cut-off voltage. The capacity retention after 200 cycles of the battery was tested and the results are shown in table 2.
Table 2: the results of the capacity retention test of the batteries with numbers S1-S5 and D1-D5.
| Group of | Capacity retention (%) |
| S1 | 95 |
| S2 | 93 |
| S3 | 92 |
| S4 | 90 |
| S5 | 91 |
| D1 | 82 |
| D2 | 79 |
| D3 | 81 |
| D4 | 83 |
| D5 | 82 |
As can be seen from tables 1 and 2, the thick pole piece made of the binder obtained by mixing the vinyl fluoride polymer and the non-crosslinked water-absorbing polymer (sodium carboxymethyl cellulose and polyvinylpyrrolidone) has a good appearance, does not shed powder, is not dissolved, and does not crack, but because of the water solubility of the two high-molecular chain binders, the binder is dissolved out with the increase of the soaking time in the electrolyte, so that the pole piece is softened, and the capacity retention rate is reduced, while the thick pole piece made of the binder obtained by mixing the vinyl fluoride polymer and the crosslinked water-absorbing polymer (crosslinked sodium carboxymethyl cellulose, crosslinked sodium polyacrylate and crosslinked polyvinylpyrrolidone) does not have the binder dissolution phenomenon.
In addition, the appearance of the thick pole piece which singly uses the vinyl fluoride polymer or the cross-linked water-absorbing polymer as the binder has certain defects, the low surface energy of PTFE influences the capacity exertion and the circulation stability of the pole piece, and the low binding power of the cross-linked water-absorbing polymer causes the phenomena of powder falling, splintering and the like of the thick pole piece, thereby influencing the capacity exertion and the circulation stability of the thick pole piece.
Variations and modifications to the above-described embodiments may occur to those skilled in the art, which fall within the scope and spirit of the above description. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims 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 (7)
1. The battery thick pole piece comprises a current collector and an active substance layer coated on the surface of the current collector, wherein the active substance layer comprises an active substance, a bonding agent and a conductive agent, and is characterized in that: the adhesive at least comprises the following components in parts by weight:
5-8 parts of vinyl fluoride polymer;
0.5-1 part by weight of a crosslinked water-absorbent polymer;
20-40 parts of water;
the vinyl fluoride polymer and the crosslinked water-absorbing polymer form an intertwined interlaced polymer network;
the preparation method of the pole piece comprises the following steps:
firstly, adding a cross-linked water-absorbing polymer into water, and fully stirring to form a cross-linked water-absorbing polymer solution; placing the conductive agent and the crosslinked water-absorbing polymer solution in a mortar for sufficient grinding to enable the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network, then adding an active substance, and performing sufficient grinding to enable the active substance, the conductive agent and the crosslinked water-absorbing polymer to form a uniform conductive network and a bonding network to obtain a mixture;
secondly, adding the vinyl fluoride polymer into water, and fully stirring to form vinyl fluoride polymer emulsion;
thirdly, adding the vinyl fluoride polymer emulsion obtained in the second step into the mixture obtained in the first step, and fully stirring to obtain semi-dry powder;
fourthly, transferring the semi-dry powder obtained in the third step onto a current collector, tabletting and drying to obtain a pole piece;
the thickness of the active material layer is 1mm-2 mm.
2. The thick battery pole piece of claim 1, wherein: the vinyl fluoride polymer is PTFE and/or PVDF.
3. The thick battery pole piece of claim 1, wherein: the crosslinked water-absorbing polymer is at least one of crosslinked sodium carboxymethylcellulose, crosslinked sodium polyacrylate and crosslinked polyvinylpyrrolidone.
4. The thick battery pole piece of claim 1, wherein: the average molecular weight of the vinyl fluoride polymer is 60-80 ten thousand.
5. The thick battery pole piece of claim 3, wherein: the average molecular weight of the croscarmellose sodium is 60-80 ten thousand, the molecular weight of the crosslinked sodium polyacrylate is 300-700 ten thousand, and the average molecular weight of the crosslinked polyvinylpyrrolidone is 4-8 ten thousand.
6. The thick battery pole piece of claim 1, wherein: the crosslinking degree of the crosslinked water-absorbing polymer is 60-85%.
7. The battery thick pole piece of claim 1, wherein the weight ratio of the active material, the conductive agent, the vinyl fluoride polymer and the crosslinked water-absorbing polymer is (75-85): 9.5-16): 5-8): 0.5-1.
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| WO2008101823A1 (en) * | 2007-02-09 | 2008-08-28 | Commissariat A L'energie Atomique | Binder for the electrode of an electro-chemical system, electrode including said binder, and electro-chemical system including said electrode |
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| WO2008101823A1 (en) * | 2007-02-09 | 2008-08-28 | Commissariat A L'energie Atomique | Binder for the electrode of an electro-chemical system, electrode including said binder, and electro-chemical system including said electrode |
| CN101447561A (en) * | 2007-11-28 | 2009-06-03 | 三星Sdi株式会社 | Negative electrode for rechargeable lithium battery, and rechargeable lithium battery including the same |
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Effective date of registration: 20220920 Address after: 519070 room 703, unit 2, building 4, No. 103, Daishan Road, Xiangzhou District, Zhuhai City, Guangdong Province Patentee after: Zhao Mingxing Address before: No.1 Factory building, Maike Industrial Park, 1888 Meijing Avenue West, xiniupi village, Dalang Town, Dongguan City, Guangdong Province, 523000 Patentee before: DONGGUAN MCNAIR NEW POWER Co.,Ltd. Patentee before: DONGGUAN MCNAIR TECHNOLOGY Co.,Ltd. Patentee before: TECHNICAL INSTITUTE OF LITHIUM BATTERY ENERGY-SAVING TECHNOLOGY OF MCNAIR, DONGGUAN. |