CN111613760A - Battery separator, battery and preparation method of battery separator - Google Patents
Battery separator, battery and preparation method of battery separator Download PDFInfo
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- CN111613760A CN111613760A CN202010468032.XA CN202010468032A CN111613760A CN 111613760 A CN111613760 A CN 111613760A CN 202010468032 A CN202010468032 A CN 202010468032A CN 111613760 A CN111613760 A CN 111613760A
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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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- 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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a battery separator, a battery and a preparation method of the battery separator, wherein the battery separator comprises: a substrate comprising a first surface and a second surface disposed in a back-to-back arrangement; the coating is coated on at least one of the first surface and the second surface and comprises first particles, the first particles comprise a silicon dioxide layer, a first polymer covers the outer surface of the silicon dioxide layer, and a containing cavity is formed in the silicon dioxide layer. An accommodating chamber is formed inside the first particles contained in the separator coating, so that a storage space can be provided for the electrolyte, the liquid retention amount of the battery separator is increased, and the infiltration degree of the battery separator is further improved; in addition, the first polymer grafted on the silicon dioxide layer can increase the adhesive force of the battery to the pole piece, maintain a good interface and improve the long-cycle performance of the battery.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a battery separator, a battery and a preparation method of the battery separator.
Background
The lithium ion battery has the characteristics of high energy density, long cycle life, no memory effect, environmental friendliness and the like, and is widely applied to products such as consumer electronics and electric tools as energy storage equipment. With the development of science and technology and the improvement of living standard, people put forward higher and higher requirements on the performance of lithium ion batteries, particularly the quick charge and discharge, long-time cycle and safety performance of the lithium ion batteries.
As an important constituent part of a lithium ion battery, a battery separator has a physical and chemical structure that has a great influence on battery performance and safety performance of the lithium ion battery. In the process of charging and discharging the lithium ion battery, lithium ions pass through the partition plate under the drive of the electrode potential to repeatedly reciprocate between the positive electrode and the negative electrode. The electrolyte is used as a main transport carrier of lithium ions, which has a decisive influence on the transport efficiency of the lithium ions, and the low amount of the electrolyte can cause the poor infiltration degree of the separator, so that the transmission rate of the lithium ions which are separated from the pole piece and pass through the separator to reach another pole piece is slowed, and the multiplying power and the cycle performance of the lithium ion battery are not facilitated.
Therefore, the battery separator in the prior art has the problem of low liquid retention.
Disclosure of Invention
The embodiment of the invention aims to provide a battery separator, a battery and a preparation method of the battery separator, and solves the problem that the battery separator in the prior art is low in liquid retention.
In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a battery separator, including:
a substrate comprising a first surface and a second surface disposed in a back-to-back arrangement;
a coating coated on at least one of the first surface and the second surface, the coating including first particles, the first particles including a silica layer, a first polymer grafted on an outer surface of the silica layer, and a receiving chamber formed inside the silica layer.
Optionally, the first polymer comprises an aliphatic polymer, or comprises an aromatic polymer, or comprises a copolymer of an aliphatic polymer and an aromatic polymer.
Optionally, the first polymer includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyether sulfone, polyethylene oxide, and polyvinylidene fluoride-hexafluoropropylene copolymer.
Optionally, the coating further comprises second particles, and the second particles are organic particles.
Optionally, the organic particles comprise an aliphatic polymer, or comprise an aromatic polymer, or comprise a blend of an aliphatic polymer and an aromatic polymer, or comprise a copolymer of an aliphatic polymer and an aromatic polymer;
optionally, the organic particles include at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyether sulfone, polyethylene oxide, and polyvinylidene fluoride-hexafluoropropylene copolymer.
Optionally, the mass of the first particles accounts for 30% -100% of the mass of the coating.
In a second aspect, embodiments of the present invention provide a battery comprising a battery separator as provided in the first aspect of embodiments of the present invention, the battery separator being disposed between a positive electrode and a negative electrode of the battery.
In a third aspect, an embodiment of the present invention provides a method for preparing a battery separator, including the following steps:
taking metal oxide or carbonic acid compound as a hard template, and obtaining hybrid particles which contain a silicon dioxide layer on the outer part and take the hard template as an inner core through hydrolysis reaction of tetraethoxysilane;
bromine modifying the outer surface of the hybrid particle;
taking the hybrid particles modified by bromine as an initiator, and grafting a first polymer on the outer surface of the hybrid particles through atom transfer radical polymerization;
etching the hard template to obtain first particles grafted with the first polymer on the outer surface of the silicon dioxide layer;
dissolving the first particles and organic particles in a solvent, and stirring and dispersing to form coating slurry;
coating the coating slurry on at least one of a first surface and a second surface of a substrate, the first surface and the second surface being oppositely disposed.
Optionally, the solvent includes one or more of water, methanol, ethanol, tetrahydrofuran, acetone, isopropanol, N-propanol, acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.
One of the above technical solutions has the following advantages or beneficial effects:
the embodiment of the invention provides a battery separator, a battery and a preparation method of the battery separator, wherein the battery separator comprises: a substrate comprising a first surface and a second surface disposed in a back-to-back arrangement; a coating coated on at least one of the first surface and the second surface, the coating including first particles, the first particles including a silica layer, a first polymer grafted on an outer surface of the silica layer, and a receiving chamber formed inside the silica layer. An accommodating chamber is formed inside the first particles contained in the separator coating, so that a storage space can be provided for the electrolyte, the liquid retention amount of the battery separator is increased, and the infiltration degree of the battery separator is further improved; in addition, the first polymer grafted on the silicon dioxide layer can increase the adhesive force of the battery separator to the pole piece, maintain a good interface and improve the long-cycle performance of the battery.
Drawings
Fig. 1 is a schematic structural diagram of a battery separator according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a first particle according to an embodiment of the present invention;
fig. 3 is a second schematic structural view of a battery separator according to an embodiment of the present invention;
fig. 4 is a third schematic structural view of a battery separator according to an embodiment of the present invention;
FIG. 5 is a schematic flow chart illustrating a method for manufacturing a battery separator according to an embodiment of the present invention;
FIG. 6 is a schematic view showing the structure of a battery separator provided in comparative example 1;
fig. 7 is a schematic view showing the structure of a battery separator provided in comparative example 2.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4, a battery separator according to an embodiment of the present invention is provided.
As shown in fig. 1 to 4, the battery separator includes:
a substrate 100, the substrate 100 comprising a first surface and a second surface arranged oppositely;
and a coating layer 200, wherein the coating layer 200 is coated on at least one of the first surface and the second surface, the coating layer 200 comprises first particles 210, the first particles 210 comprise a silica layer 211, a first polymer 213 is grafted on the outer surface of the silica layer 211, and a containing cavity 212 is formed inside the silica layer 211.
The substrate 100 is a porous substrate, and a plurality of through holes are formed in the porous substrate, so that the electrolyte passes through the battery separator and reaches another electrode plate from one electrode plate of the battery, and charging and discharging of the battery are realized. Specifically, the substrate 100 may be a single-layer polyethylene porous film of 3 to 20um, a single-layer polypropylene porous film, or a porous film of a polyethylene polypropylene composite two-layer or multi-layer structure, which is not limited herein.
The coating 200 is applied to at least one surface of the substrate 100 that is disposed opposite to the first surface, and specifically, two surfaces of the substrate 100 that are disposed opposite to the second surface are respectively referred to as a first surface and a second surface, and the coating 200 is applied to at least one of the first surface and the second surface. In some embodiments, as shown in fig. 1, the coating 200 is applied to the first and second surfaces of the substrate 100.
In an embodiment of the present invention, the coating 200 includes first particles 210. As shown in fig. 2, the first particle 210 has a silicon dioxide layer 211, and the silicon dioxide layer 211 can improve mechanical properties of the first particle 210 and ensure a stable structure of the first particle 210. Meanwhile, the accommodating chamber 212 is formed in the silicon dioxide layer 211 in a hollow mode, the accommodating chamber 212 has a certain storage space and can be used for accommodating electrolyte of a battery, the liquid retaining amount of the battery separator is increased, the infiltration degree of the battery separator is improved, lithium ions can be transmitted between the positive pole piece and the negative pole piece conveniently, the long-term cycle performance of the battery is improved, and the service life of the battery is prolonged.
In addition, the first polymer 213 is grafted outside the silicon dioxide layer 211, and the first polymer 213 can increase the adhesive force of the surface of the first particle 210, thereby increasing the adhesive force of the surface of the coating 200, maintaining good wetting between the battery separator and the pole piece, and improving the long cycle performance of the battery.
The first particles 210 may include, in addition to the silica layer, an inorganic substance having a hydroxyl group on the surface thereof or capable of being chemically modified to hydroxylate the surface, such as titanium dioxide or calcium carbonate, as an intermediate layer, and are not limited thereto.
According to the battery separator provided by the embodiment of the invention, the accommodating chamber 212 is formed inside the first particles 210 contained in the separator coating layer 200, so that the storage space is provided for the electrolyte, the liquid retention capacity of the battery separator is increased, and in addition, the adhesion of the battery separator is further improved and the long-cycle performance of the battery is improved through the first polymer 213 grafted outside the silicon dioxide layer 211.
Optionally, the first polymer 213 comprises an aliphatic polymer, or comprises an aromatic polymer, or comprises a copolymer of an aliphatic polymer and an aromatic polymer.
Preferably, the first polymer 213 includes at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyether sulfone, polyethylene oxide, and polyvinylidene fluoride-hexafluoropropylene copolymer.
In this embodiment, the first polymer 213 of the above-mentioned composition may be in the form of hair, and as shown in fig. 2, the hair-like first polymer 213 increases the contact area between the silicon dioxide layer 211 and the electrolyte inside the battery, thereby increasing the wetting degree of the battery separator. In one embodiment, the battery separator is shown in fig. 3, and the coating layer 200 including the first particles 210 is applied to the first surface and the second surface of the substrate 100.
Optionally, as shown in fig. 3 and 4, the coating 200 further includes second particles 220, and the second particles 220 are organic particles.
In this embodiment, the coating 200 is formed by mixing the first particles 210 and the second particles 220, and the organic particles 220 can serve as a binder to enhance the binding force between the first particles 210 and the first particles 210, thereby ensuring the stability and strength of the coating 200.
In some embodiments, the organic particles 220 comprise aliphatic polymers, aromatic polymers, or mixtures of the two, or copolymers of the two. Further, the organic particles 220 include at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyether sulfone, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer.
Optionally, the mass of the first particles 210 is 30-100% of the mass of the coating 200.
In this embodiment, since the coating layer 200 may further include other components such as an organic binder, the mass of the first particles 210 may account for 30 to 100% of the mass of the coating layer 200.
Alternatively, as shown in fig. 4, a second surface of the substrate 100 is covered with a layer of inorganic particles 300, the layer of inorganic particles 300 includes a third surface and a fourth surface which are oppositely arranged, the third surface is in contact with the second surface, and the coating 200 is coated on at least one of the first surface and the fourth surface.
In the prior art, in order to reduce the internal resistance and volume of the battery, the positive and negative plates are usually close to each other, and the battery separator is arranged between the positive and negative plates of the battery to perform an insulating function, so as to prevent the positive and negative electrodes of the battery from being short-circuited. The temperature inside the battery is often higher due to heat release in the charging and discharging processes of the battery, and the substrate is usually made of organic materials and is easy to shrink when being heated, so that the risk of contact short circuit of the positive and negative pole pieces of the battery is increased.
In this embodiment, the second surface of the substrate 100 is covered with a layer of inorganic particle layer 300, as shown in fig. 4, the inorganic particle layer 300 has certain heat resistance, and when the internal temperature of the battery rises, the substrate 100 can be protected to reduce the overall shrinkage of the battery separator, and the risk of contact short circuit of the positive and negative electrode plates of the battery is reduced.
Wherein the inorganic particle layer 300 may be composed of inorganic particles, and the inorganic particles may be composed of one or more kinds of particles including, but not limited to, silica, boehmite, alumina, zinc oxide, zirconia, titania; in addition, in order to enhance the adhesive force between the inorganic particles and the substrate 100, the inorganic particles may be mixed with the organic binder at a certain mass ratio. The inorganic particles may account for 50% to 99% by mass of the inorganic particle layer 300, and the organic binder may account for 1% to 50% by mass of the inorganic particle layer 300, which is not limited herein.
Wherein the organic binder can be one or more of carboxymethyl cellulose (CMC), polyvinylidene fluoride, polyacrylonitrile, polyvinyl alcohol, styrene butadiene rubber, polyurethane, polyacrylate, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer.
In one embodiment, as shown in fig. 4, the coating layer 200 including the first particles 210 is coated on the first surface of the substrate 100 and the fourth surface of the inorganic particle layer 300.
Optionally, the diameter of the receiving chamber 212 is 10-1000 nm.
In this embodiment, the diameter of the accommodating chamber 212 is limited to 10-1000nm, so as to ensure that the accommodating chamber 212 can accommodate a certain amount of electrolyte, and at the same time, ensure that the first particles 210 are not structurally damaged due to the excessively large aperture of the accommodating chamber 212.
Optionally, the thickness of the silicon dioxide layer 211 is 10-1000 nm.
In this embodiment, the thickness of the silicon dioxide layer 211 is limited to 10-1000nm, so as to ensure that the mass of the first particles 210 is not too heavy due to the too large thickness of the silicon dioxide layer 211, which causes uneven distribution of the coating slurry.
In summary, according to the battery separator provided by the embodiments of the present invention, the accommodating chamber is formed inside the first particle included in the separator coating layer, so as to provide a storage space for the electrolyte, and increase the liquid retention capacity of the battery separator.
Embodiments of the present invention also provide a battery including a battery separator provided as in the embodiments of fig. 1, 3, and 4 above, the battery separator being disposed between a positive electrode and a negative electrode of the battery. The battery provided by the embodiment of the invention comprises all the technical characteristics of the battery separator and can achieve the same technical effect.
In the embodiment of the invention, by adopting the battery separator provided by the embodiment shown in fig. 1, fig. 3 and fig. 4, the first particles contained in the separator coating are internally provided with the accommodating chambers, so that a storage space can be provided for electrolyte, the liquid retention capacity of the battery separator is increased, in addition, the first polymer grafted outside the silica layer further improves the binding power of the battery separator, keeps a good interface between the separator and a pole piece, and improves the long-cycle performance of the battery.
Referring to fig. 5, an embodiment of the invention provides a method for manufacturing a battery separator. As shown in fig. 5, the method comprises the steps of:
Specifically, metal oxide or carbonate can be used as a hard template, ammonia water, a surfactant and tetraethoxysilane are added, stirred, reacted and centrifugally washed, and the hybrid particle containing a silicon dioxide shell and taking the hard template as an inner core is obtained.
In this step, in the embodiment of the present invention, based on a hard template method, based on the principle that tetraethoxysilane can be hydrolyzed under an alkaline condition to form a silica sphere, a metal oxide or a carbon compound is used as a hard template, tetraethoxysilane is added as a silicon source, ammonia water is added as a catalyst to form an alkaline environment, a surfactant is added to form a porous structure in a silica layer when tetraethoxysilane is hydrolyzed, and the mixture is stirred at room temperature for reaction for 12 to 18 hours to generate a porous hybrid particle including a silica shell and an inner core of the porous hybrid particle being a metal oxide or a carbon compound. Since the reaction solvent in the subsequent step is different from that in the present step, the obtained porous hybrid particles need to be washed away by centrifugation to obtain dispersed porous hybrid particles.
In the step, the porous hybrid particles are re-dispersed uniformly, and the surface of the porous hybrid particles is modified by using a bromine functional group through silane coupling, triethylamine and 2-bromoisobutyryl bromide. Specifically, a silane coupling agent with amino groups can be added to modify the amino groups on the surface of the hybrid particles, triethylamine and 2-bromoisobutyryl bromide are added to modify the bromine groups on the surface of the hybrid particles, and the bromine functional groups on the surface of the hybrid particles are modified to provide grafting points of the first polymer.
Specifically, the hybrid particle modified with bromine can be used as an initiator, copper bromide, cuprous bromide, N', N "-pentamethyldivinyltriamine and a monomer are added, and a first polymer is grafted on the outer surface of the hybrid particle.
In this step, since part of the polymer generated by the polymerization initiated in step 503 may not be grafted on the silica shell of the hybrid particle, it can be removed by using a good solvent for these polymers, and then purified by centrifugation. Then, the hard template is etched by strong acid to remove the metal oxide or carbonate core in the hybrid particles, so as to obtain first particles which include a silica shell and have a hollow interior and a receiving chamber, as shown in fig. 2. The strong acid may be hydrochloric acid or sulfuric acid, and the like, and is not limited herein.
And 505, dissolving the first particles and the organic particles in a solvent, and stirring and dispersing to form coating slurry.
In this step, the obtained first particles and organic particles may be dissolved in a solvent, stirred and dispersed, and then sufficiently mixed and sieved to obtain a coating slurry.
Optionally, the solvent includes, but is not limited to, one or a mixture of water, methanol, ethanol, tetrahydrofuran, acetone, isopropanol, N-propanol, acetonitrile, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and N-methylpyrrolidone.
Further, the mass ratio of the first particles in the coating slurry is 30-100%
In this embodiment, the mass of the first particles may be 30 to 100% of the mass of the mixed slurry, and the mass of the organic particles may be 0 to 70% of the mass of the mixed slurry, which is not limited herein.
In this embodiment, the organic particles can be used as a binder to make the first particles fully and uniformly dispersed and enhance the binding force between the first particles, thereby ensuring the stability and strength of the coating. Wherein, the organic particles can be one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, butyl acrylate-acrylonitrile copolymer, polyacrylonitrile, ethylene-acrylic acid copolymer, polyethyl acrylate and sodium carboxymethylcellulose.
In this step, the coating slurry obtained in step 505 may be coated on at least one of the first surface and the second surface of the substrate, which are opposite to each other, by gravure coating, transfer coating, cast coating, extrusion coating, spray coating, or the like using an automatic coating machine, and dried in a vacuum oven, so as to obtain the battery separator provided in the embodiment of the present invention. The temperature of the vacuum oven can be controlled to be 60-160 ℃, and the drying time of the vacuum oven can be controlled to be 1-48 hours, which is not limited herein.
Optionally, before the applying the coating slurry on at least one of the first surface and the second surface of the substrate, the method further comprises:
mixing alumina ceramic particles with a polyvinylidene fluoride solution to obtain ceramic slurry;
coating the ceramic slurry on the second surface of the substrate to form an inorganic particle layer;
the coating of the coating slurry on at least one of the first and second surfaces of the substrate comprises:
applying the coating slurry on at least one of a first surface of the substrate and a surface of the inorganic particle layer facing away from the substrate.
In this embodiment, before the coating slurry is applied to the substrate, the second surface of the substrate is further coated with an inorganic particle layer, as shown in fig. 4. The inorganic particle layer has certain heat resistance, and can protect the substrate to weaken the integral shrinkage of the battery separator and reduce the risk of contact short circuit of the positive and negative pole pieces of the battery under the condition that the internal temperature of the battery rises.
Specifically, the slurry of the inorganic particle layer may be a ceramic slurry obtained by mixing alumina ceramic particles with a polyvinylidene fluoride solution, and the inorganic particle layer may be formed by coating the ceramic slurry on the second surface of the substrate by a method such as gravure coating, transfer coating, curtain coating, extrusion coating, or spray coating using an automatic coating machine, and sufficiently drying the coated ceramic slurry.
It should be noted that, the methods of gravure coating, transfer coating, cast coating, extrusion coating, or spray coating, etc. can refer to the conventional processes in the art, and are not described herein again.
A full example of an embodiment of the present invention and its comparative example are described below:
example 1, example 1 a battery separator as shown in fig. 3 was prepared:
1) preparation of first particles
Dispersing 0.2g of ferroferric oxide nanoparticles (the particle size is 150nm) in 140mL of absolute ethyl alcohol, adding 2mL of ammonia water, 40mL of deionized water and a surfactant, dropwise adding 0.5mL of ethyl orthosilicate within 1 hour under the action of mechanical stirring, and reacting at room temperature for 12 hours to obtain porous hybrid particles with a ferroferric oxide core and a silicon dioxide shell;
dispersing the porous hybrid particles in a solvent containing 60mL of ethanol, 20mL of water, 1mL of ammonia water and 1mL of 3-aminopropyltriethoxysilane, uniformly mixing, and reacting at 80 ℃ for 2 hours to obtain amino-modified porous hybrid particles;
re-dispersing the amino modified porous hybrid particles in anhydrous trichloromethane, introducing nitrogen to remove oxygen for 30 minutes, adding triethylamine, stirring uniformly, placing at 0 ℃ and slowly dropwise adding 2-bromoisobutyryl bromide, reacting for 3 hours, and then transferring to normal temperature to react for 48 hours to obtain bromine modified porous hybrid particles;
taking the bromine-modified porous hybrid particles as an initiator, adding a certain proportion of copper bromide, cuprous bromide, N, N, N ', N ', N ' -pentamethyl divinyl triamine and monomer methyl methacrylate, and initiating polymerization to graft polymethyl methacrylate on the outer surface of the porous hybrid particles. And then, completely etching and removing the ferroferric oxide core of the porous hybrid particle by using hydrochloric acid to obtain the first particle which is provided with a silicon dioxide shell, is grafted with polymethyl methacrylate at the outer part and is hollow at the inner part to form a containing chamber.
2) Preparation of coating slurries
The first particles prepared above and polyvinylidene fluoride were prepared into a slurry at a mass ratio of 70:30 using a porous film of polyolefin as a substrate and polyvinylidene fluoride as a binder.
3) Application of coating paste
The coating slurry obtained above was applied to the first and second surfaces of the substrate by means of gravure coating, and after sufficient drying, coatings each having a thickness of 1 μm were formed, thereby producing a battery separator.
Comparative example 1, comparative example 1 a battery separator as shown in fig. 6 was prepared:
1) preparation of coating slurries
Preparing polyvinylidene fluoride into slurry.
2) Application of coating paste
The coating slurry obtained above was applied to the first and second surfaces of the substrate by gravure coating, and after sufficient drying, coatings each having a thickness of 1 μm were formed.
Example 1 with respect to comparative example 1, a receiving chamber is formed inside the first particles included in the separator coating layer to provide a space for storing an electrolyte, increasing the amount of the electrolyte retained by the battery separator, and thus increasing the degree of wetting of the battery separator and improving the long cycle performance of the battery.
Another complete example of this embodiment and its comparative example are described below:
example 2, example 2 a battery separator as shown in fig. 4 was prepared:
1) preparation of first particles
Dispersing 0.2g of ferroferric oxide nanoparticles (the particle size is 150nm) in 140mL of absolute ethyl alcohol, adding 2mL of ammonia water, 40mL of deionized water and a surfactant, dropwise adding 0.5mL of ethyl orthosilicate within 1 hour under the action of mechanical stirring, and reacting at room temperature for 12 hours to obtain porous hybrid particles with a ferroferric oxide core and a silicon dioxide shell;
dispersing the porous hybrid particles in a solvent containing 60mL of ethanol, 20mL of water, 1mL of ammonia water and 1mL of 3-aminopropyltriethoxysilane, uniformly mixing, and reacting at 80 ℃ for 2 hours to obtain amino-modified porous hybrid particles;
re-dispersing the amino modified porous hybrid particles in anhydrous trichloromethane, introducing nitrogen to remove oxygen for 30 minutes, adding triethylamine, stirring uniformly, placing at 0 ℃ and slowly dropwise adding 2-bromoisobutyryl bromide, reacting for 3 hours, and then transferring to normal temperature to react for 48 hours to obtain 3 modified porous hybrid particles;
taking the bromine-modified porous hybrid particles as an initiator, adding a certain proportion of copper bromide, cuprous bromide, N, N, N ', N ', N ' -pentamethyl divinyl triamine and monomer methyl methacrylate, and initiating polymerization to graft polymethyl methacrylate on the outer surface of the porous hybrid particles. And then, completely etching and removing the ferroferric oxide core of the porous hybrid particle by using hydrochloric acid to obtain the first particle which is provided with a silicon dioxide shell, is grafted with polymethyl methacrylate at the outer part and is hollow at the inner part to form a containing chamber.
2) Preparation of inorganic particle layer
Using a polyolefin porous membrane as a substrate, alumina ceramic particles were thoroughly mixed with a polyvinylidene fluoride solution to obtain a ceramic slurry. And then coating alumina ceramic particles on a second surface of the substrate by adopting a gravure coating mode, wherein the second surface is the lower surface of the substrate as shown in figure 4, and fully drying to obtain an inorganic particle coating with the thickness of 2 mu m.
3) Preparation of coating slurries
Polyvinylidene fluoride is selected as a binder, and the prepared first particles and polyvinylidene fluoride are prepared into slurry according to the mass ratio of 70: 30.
4) Application of coating paste
The coating slurry obtained above was coated on the first surface of the substrate and the fourth surface of the inorganic particle layer by means of gravure coating, as shown in fig. 4, the first surface being the upper surface of the substrate and the fourth surface being the lower surface of the inorganic particle layer, and after sufficient drying, coatings each having a thickness of 1 μm were formed, thereby producing a battery separator.
Comparative example 2, comparative example 2 a battery separator as shown in fig. 7 was prepared:
1) preparation of inorganic particle layer
Using a polyolefin porous membrane as a substrate, alumina ceramic particles were thoroughly mixed with a polyvinylidene fluoride solution to obtain a ceramic slurry. And then coating alumina ceramic particles on a second surface of the substrate by adopting a gravure coating mode, wherein the second surface is the lower surface of the substrate as shown in figure 4, and fully drying to obtain an inorganic particle coating with the thickness of 2 mu m.
2) Preparation of coating slurries
Preparing polyvinylidene fluoride into slurry.
3) Application of coating paste
The coating slurry obtained above was coated on the first surface of the substrate and the fourth surface of the inorganic particle layer by means of gravure coating, as shown in fig. 4, the first surface being the upper surface of the substrate and the fourth surface being the lower surface of the inorganic particle layer, and after sufficient drying, coatings each having a thickness of 1 μm were formed, thereby producing a battery separator.
In example 2, compared to comparative example 2, a containing chamber is formed inside the first particles contained in the separator coating layer to provide a space for storing an electrolyte, so that the liquid retention amount of the battery separator is increased, the wetting degree of the battery separator is further improved, and the long cycle performance of the battery is improved; meanwhile, the first particles with hollow interiors can reduce the overall weight of the separator and improve the energy density of the battery.
In addition, the preparation of a battery including the battery separator provided in the embodiment shown in fig. 1, 3 and 4 as described above may be accomplished according to the following steps:
1) preparation of positive plate
Mixing a positive electrode active material lithium cobaltate, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVDF) according to a weight ratio of 96: 2: and 2, sufficiently and uniformly mixing the materials in the solvent to form positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, drying, rolling, cutting pieces, and welding lugs to obtain the positive electrode piece. The processes of positive current collector, drying, rolling and cutting pieces and welding the tabs can refer to conventional processes in the field, and are not described herein again.
2) Preparation of negative plate
Mixing the negative active material artificial graphite, the conductive agent acetylene black, the binder Styrene Butadiene Rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) according to a ratio of 96: 1.5: 1.5: 1, uniformly mixing the mixture in a solvent to form negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, drying, rolling, cutting pieces, and welding tabs to obtain a negative electrode piece. The negative current collector, drying, rolling and cutting the sheet and welding the tab can refer to the conventional process in the field, and are not described herein again.
3) Preparation of the electrolyte
In an inert gas atmosphere glove box, Ethylene Carbonate (EC), diethyl carbonate (DEC), Propylene Carbonate (PC) were mixed in a ratio of 30: 65: 5, and then adding 15 percent of lithium hexafluorophosphate into the mixed solution according to the total mass of the electrolyte.
4) Preparation of the Battery
And sequentially winding the positive plate, the battery partition plate and the negative plate into a bare cell, placing the bare cell in an outer packaging foil, carrying out top sealing and side sealing, injecting an electrolyte into the dried battery, and carrying out vacuum packaging, standing, formation, shaping and other procedures to obtain the battery. The processes of vacuum packaging, standing, formation, shaping and the like can refer to conventional processes in the field, and are not described herein again.
In summary, the battery separator including the first particles can be prepared by the preparation method of the battery separator provided by the embodiment of the invention, the first particles are internally provided with the accommodating chambers, so that the accommodating chambers can provide a storage space for electrolyte, the liquid retaining amount of the battery separator is increased, and in addition, the first polymer covered outside the silicon dioxide layer further improves the binding power of the battery separator, so that the infiltration degree of the battery separator is improved, and the long cycle performance of the battery is improved.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A battery separator, comprising:
a substrate comprising a first surface and a second surface disposed in a back-to-back arrangement;
a coating coated on at least one of the first surface and the second surface, the coating including first particles, the first particles including a silica layer, a first polymer grafted on an outer surface of the silica layer, and a receiving chamber formed inside the silica layer.
2. The battery separator of claim 1, wherein the first polymer comprises an aliphatic polymer, or comprises an aromatic polymer, or comprises a copolymer of an aliphatic polymer and an aromatic polymer.
3. The battery separator of claim 2, wherein the first polymer comprises at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethersulfone, polyethylene oxide, and polyvinylidene fluoride-hexafluoropropylene copolymer.
4. The battery separator of claim 1, wherein the coating further comprises second particles, the second particles being organic particles.
5. The battery separator of claim 4, wherein the organic particles comprise an aliphatic polymer, or comprise an aromatic polymer, or comprise a blend of an aliphatic polymer and an aromatic polymer, or comprise a copolymer of an aliphatic polymer and an aromatic polymer.
6. The battery separator according to claim 5, wherein the organic particles comprise at least one of polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, polyethersulfone, polyethylene oxide, and polyvinylidene fluoride-hexafluoropropylene copolymer.
7. The battery separator of claim 1, wherein the mass of the first particles is 30% to 100% of the mass of the coating.
8. A battery comprising the battery separator of any one of claims 1 to 7 disposed between a positive electrode and a negative electrode of the battery.
9. A method for preparing a battery separator, comprising the steps of:
taking metal oxide or carbonic acid compound as a hard template, and obtaining hybrid particles which contain a silicon dioxide layer on the outer part and take the hard template as an inner core through hydrolysis reaction of tetraethoxysilane;
bromine modifying the outer surface of the hybrid particle;
taking the hybrid particles modified by bromine as an initiator, and grafting a first polymer on the outer surface of the hybrid particles through atom transfer radical polymerization;
etching the hard template to obtain first particles grafted with the first polymer on the outer surface of the silicon dioxide layer;
dissolving the first particles and organic particles in a solvent, and stirring and dispersing to form coating slurry;
coating the coating slurry on at least one of a first surface and a second surface of a substrate, the first surface and the second surface being oppositely disposed.
10. The method according to claim 9, wherein the solvent comprises one or more of water, methanol, ethanol, tetrahydrofuran, acetone, isopropanol, N-propanol, acetonitrile, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and N-methylpyrrolidone.
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| CN116345063A (en) * | 2023-05-31 | 2023-06-27 | 合肥长阳新能源科技有限公司 | Coated lithium battery diaphragm, preparation method thereof and lithium battery |
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