CN114243208A - Composite diaphragm, preparation method thereof and secondary battery - Google Patents
Composite diaphragm, preparation method thereof and secondary battery Download PDFInfo
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- CN114243208A CN114243208A CN202111442819.XA CN202111442819A CN114243208A CN 114243208 A CN114243208 A CN 114243208A CN 202111442819 A CN202111442819 A CN 202111442819A CN 114243208 A CN114243208 A CN 114243208A
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a composite diaphragm and a preparation method thereof, and a secondary battery, wherein the preparation method of the composite diaphragm comprises the following steps: step S1, adding the inorganic filler, the dispersant and the thickener into the solvent, mixing and dispersing, and grinding to obtain grinding fluid; step S2, adding the adhesive into the grinding fluid, stirring and dispersing to obtain a premixed solution; step S3, adding the compression-resistant binder into the pre-mixed liquid, stirring and dispersing to obtain blended slurry; and step S4, coating the blended slurry on at least one surface of the base film, and drying to form a coating layer to obtain the composite diaphragm.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a composite diaphragm, a preparation method of the composite diaphragm and a secondary battery.
Background
The lithium ion battery diaphragm is an important component of the lithium ion battery, is arranged between the positive electrode and the negative electrode of the battery, prevents the direct contact of active substances of the positive electrode and the negative electrode to cause short circuit, can adsorb electrolyte and transmit lithium ions, and plays an important role in the safety performance, the cycle performance, the internal resistance, the charge and discharge performance and the like of the battery.
With the increasing demand of terminal customers on lithium ion charging multiplying power, the requirements on high dynamic performance and safety performance of the isolating membrane are both provided. Currently, release films are usually formed by coating one or two inorganic ceramic layers on the top surface of a base film and then coating a polymer adhesive layer on the outside. The coating mode has stable heat resistance and good adhesion, but polymer particles on the surface can swell after being soaked by electrolyte, and the polymer particles are easy to adhere to the surface of the diaphragm to form a film after hot pressing in a formation process to form a hole plug, so that the transmission of free electrolyte between the isolating film and the pole piece is not timely in the circulation process, the circulation performance is poor, black spots on the surface of the anode are easy to precipitate lithium after long circulation, and the circulation life of the lithium ion battery is seriously influenced. On the other hand, in order to increase the battery ED as much as possible, the lithium battery separator used in the digital field generally compresses the thickness of the coating layer of the separator within 3 μm, so that the separator generally can only keep stable at 130 ℃, and the size of the separator is severely shrunk at 150 ℃ or above, which cannot meet the high-performance safety requirements of the battery.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the preparation method of the composite diaphragm is provided, so that the risk of blocking the pores by the adhesion of the adhesive particles to form the film is effectively reduced, the heat resistance of the diaphragm is improved, and the cycle and safety performance of the battery are improved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a composite diaphragm comprises the following steps:
step S1, adding the inorganic filler, the dispersant and the thickener into the solvent, mixing and dispersing, and grinding to obtain grinding fluid;
step S2, adding the adhesive into the grinding fluid, stirring and dispersing to obtain a premixed solution;
step S3, adding the compression-resistant binder into the pre-mixed liquid, stirring and dispersing to obtain blended slurry;
and step S4, coating the blended slurry on at least one surface of the base film, and drying to form a coating layer to obtain the composite diaphragm.
The composite diaphragm of the invention forms a composite coating containing inorganic filler with higher specific surface area and smaller particle size and a compression-resistant binder on a porous base membrane, the compression-resistant binder can play a role in supporting and binding, the inorganic filler has higher specific surface area, the composite coating can be stabilized and the heat resistance of the coating can be improved, meanwhile, the inorganic filler has smaller particle size and can be filled between the compression-resistant binders to play a role in spacing, so that the compression-resistant binder is directly adhered to a film after being compressed, and the cycle performance is improved.
Preferably, the compression-resistant binder is a modified PMMA microsphere, the modified PMMA microsphere has a stable core-shell structure and can play a supporting role, and an external shell plays a bonding role.
The modified PMMA microspheres comprise the following steps:
1) adding an emulsifier into the first monomer for pre-emulsification, and adding a solvent to form a first monomer emulsion with the concentration of 20-70%; adding an emulsifier into the second monomer for pre-emulsification, and adding a solvent to form a second monomer emulsion with the concentration of 20-70%; dropwise adding a first monomer emulsion into the first initiator solution with the concentration of 0.5-5%, and reacting at 60-90 ℃ for 0.5-3 h to obtain a nuclear layer emulsion;
adding 0.5-5% of second initiator solution into the core layer emulsion obtained in the step 1), then dropwise adding the second monomer emulsion obtained in the step 1), reacting at 60-90 ℃, reacting for 1-3 h, cooling to 20-40 ℃, and drying to obtain the modified PMMA microspheres.
Wherein the first monomer is one or a composition of more than two of ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-hydroxyethyl acrylate, hexyl methacrylate or butadiene; the second monomer is one or a composition of more than two of methyl methacrylate, methyl acrylate, acrylic ester, acrylonitrile, methacrylic acid, acrylic acid or acrylamide; the emulsifier is one or a composition of more than two of AEO-7, AEO-9, OP-10, SDS, polyethylene glycol 200-400, Tween-80 or polyvinyl alcohol 1799; the first initiator is one or a composition of more than two of potassium persulfate, ammonium persulfate, sodium persulfate, dibenzoyl peroxide or cumene hydroperoxide composite ferrous ion polymer; the solvent is one or a composition of more than two of water, ethanol or isopropanol. The dosage of the emulsifier used by the first monomer is 1-10 wt% of the mass of the first monomer. The amount of the first initiator is 1-5 wt% of the mass of the first monomer. The water-based polymer glue contains polar functional groups, wherein the polar functional groups are one or more than two of hydroxyl, carboxyl, ester groups, amide groups and nitrile groups; the water-based polymer glue is one or a composition of more than two of polyacrylic acid, polyacrylic acid-isooctyl acrylate copolymer, polyacrylic acid-acrylonitrile copolymer, carboxylated modified polyacrylamide or carboxylated modified polystyrene-butadiene copolymer; the suspension stabilizer is one or more of polyvinyl alcohol, sodium carboxymethylcellulose, polyvinylpyrrolidone, gelatin, alginic acid or PEG-150. The suspension stabilizer can form intermolecular acting force with the high-bonding-force polymer dispersion liquid, can also increase the viscosity of the slurry, prevent polymer particles from settling and ensure the stable and uniform characteristics of the slurry. The auxiliary agent is one or a combination of more than two of fatty alcohol polyoxyethylene ether AEO-7, fatty alcohol polyoxyethylene ether AEO-9, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, polyoxyethylene polyoxypropylene block copolymer, modified polysiloxane or acetylene glycol ethoxy compound. The auxiliary agent is mainly a nonionic surfactant which improves the wetting and leveling performance of the high-adhesion polymer slurry on the surface of the base film and has good stability. The slurry solvent is one or a composition of more than two of water, ethanol, isopropanol or dimethyl carbonate.
Specifically, the weight part ratio of the inorganic filler, the dispersing agent, the thickening agent, the adhesive, the compression-resistant binder and the solvent is 80-99: 0.1-3: 0.1-5: 1-10: 1-20: 50-80 parts. Preferably, the weight part ratio of the inorganic filler to the dispersant to the thickener to the adhesive to the compression-resistant binder to the solvent is 75-99: 1-3: 1-5: 3-10: 5-20: 50-80, preferably, the weight part ratio of the inorganic filler, the dispersing agent, the thickening agent, the adhesive, the compression-resistant binder and the solvent is 80-99: 0.1-2: 1-4: 1-6: 1-10: 60-80. Within the above range, the manufactured separator has good heat resistance, cycle performance and safety.
Specifically, in the step S3, the compression-resistant binder is added to the pre-mixed solution, stirred and dispersed, and 0.1 to 20 parts by weight of the wetting agent is added, mixed and dispersed to obtain the blending slurry. By adding the wetting agent, the surface tension of the compression-resistant binder can be reduced, so that the compression-resistant binder and the premix are dissolved more fully and dispersed.
Specifically, the particle size D50 of the inorganic filler is 0.08-2 mu m, and the specific surface area is 10-100 m2(ii) in terms of/g. Preferably, the particle size D50 is 0.1-0.5 μm, more preferably, the particle size D50 is 0.1-0.3 μm; preferably, the specific surface area is 10-50 m2A specific surface area of 10 to 20 m/g2/g。
Specifically, the compression ratio of the compression-resistant adhesive is 30-80%. Preferably, the compression ratio of the compression-resistant binder is 40% to 60%, preferably 50% to 55%.
Specifically, the compression-resistant binder is polyacrylate modified polymethyl methacrylate. The compression-resistant binder disclosed by the invention has moderate electrolyte swelling degree, excellent long-acting electrolyte resistance stability and no blockage of diaphragm micropores.
Specifically, the thickness of the base film is 3-20 um, the porosity is 25% -55%, and the air permeability is 70-200 s/100 cc. More preferably, the thickness is 3 to 10 μm, the porosity is 30 to 45%, and the air permeability is 90 to 150s/100 cc.
Specifically, the inorganic filler includes at least one of alumina, boehmite, magnesium hydroxide, aluminum hydroxide, magnesium oxide, calcium oxide, silica; the dispersing agent comprises at least one of polyacrylic acid and sodium salt thereof, polyacrylamide, polyvinyl alcohol, sodium citrate, sodium ethylene diamine tetracetate, sodium diacetate, sodium hexametaphosphate and sodium silicate; the thickening agent comprises at least one of hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, sodium carboxymethyl cellulose, methyl cellulose and sodium alginate; the wetting agent comprises at least one of alkylphenol polyoxyethylene, alkyl sodium sulfonate, alkyl aryl sodium sulfonate and alkyl sodium sulfate; the adhesive comprises a hydrophilic monomer, wherein the hydrophilic monomer comprises at least one of acrylic acid, methacrylic acid, acrylamide, vinyl alcohol and hydroxyethyl acrylate.
The second purpose of the invention is: aiming at the defects of the prior art, the composite diaphragm is provided, the risk of blocking holes caused by adhesion of adhesive layer particles during film formation is effectively improved, and the composite diaphragm has good thermal stability, circulation and safety.
In order to achieve the purpose, the invention adopts the following technical scheme:
a composite diaphragm is prepared by the preparation method of the composite diaphragm. The composite diaphragm prepared by the invention has good adhesion, can effectively reduce the risk of forming circulating diving by adhesion and film formation of an adhesive layer, improves the 150 ℃ heat shrinkage resistance, and can realize one-step molding by using only one slurry, thereby improving the production efficiency and the product consistency.
The third purpose of the invention is that: aiming at the defects of the prior art, the secondary battery is provided, has good heat resistance, good cyclicity and good safety, and effectively reduces the risk of blocking pores due to the adhesion of adhesive layer particles.
In order to achieve the purpose, the invention adopts the following technical scheme:
a secondary battery comprises the composite diaphragm. Specifically, a secondary battery, includes positive plate, negative plate, compound diaphragm, electrolyte and casing, compound diaphragm separates positive plate with the negative plate, the casing is used for installing positive plate, negative plate, compound diaphragm and electrolyte.
Compared with the prior art, the invention has the beneficial effects that: the composite diaphragm of the invention forms a composite coating containing inorganic filler with higher specific surface area and smaller particle size and a compression-resistant binder on a porous base membrane, the compression-resistant binder can play a role in supporting and binding, the inorganic filler has higher specific surface area, the composite coating can be stabilized and the heat resistance of the coating can be improved, meanwhile, the inorganic filler has smaller particle size and can be filled between the compression-resistant binders to play a role in spacing, so that the compression-resistant binder is directly adhered to a film after being compressed, and the cycle performance is improved.
Drawings
Fig. 1 is a schematic view of the assembly of the composite separator of the present invention with a positive electrode sheet and a negative electrode sheet.
Wherein: 1. an inorganic filler; 2. a compression resistant binder; 3. a positive plate; 4. a base film; 5. and a negative plate.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
Example 1
(1) 80 parts by weight of D50 is taken as 0.3 mu m, and the specific surface area (BET) is 13m2Uniformly dispersing 1/g of inorganic filler, 55 parts of deionized water, 1.5 parts of dispersant and 2 parts of thickener for 30min at a high rotating speed of 2500rpm, and then obtaining slurry dispersion liquid;
(2) placing the slurry dispersion liquid obtained in the step (1) in grinding equipment, controlling the flow at 1000L/h and the rotating speed at 750rpm, and grinding for 60min to obtain grinding liquid;
(3) adding 6 parts of adhesive into the slurry grinding fluid obtained in the step (2), uniformly dispersing at the rotating speed of 1500rpm for 20min to obtain a premixed fluid, adding 5 parts of compression-resistant binder 2 (modified PMMA microspheres) into the premixed fluid, performing low-speed dispersion at 800rpm for 30min, and adding 0.1 part of wetting agent to obtain a blended slurry;
(4) and (3) uniformly coating the blended slurry in the step (3) on polyethylene microporous membranes serving as two sides of the base membrane 4, wherein the total thickness of the coating is 3 microns, and then drying in an oven at 50 ℃ to obtain the composite diaphragm, as shown in figure 1.
The inorganic filler 1 is alumina powder, the dispersing agent is sodium polyacrylate, the thickening agent is sodium carboxymethylcellulose, the adhesive is acrylate, the wetting agent is alkylphenol polyoxyethylene, the compression ratio of the modified PMMA microspheres is 50%, the particle size D50 is 3 micrometers, the thickness of the polyethylene microporous membrane is 5 micrometers, the porosity is 35%, and the ventilation center value is 140s/100 cc.
Example 2
The difference from example 1 is that: the specific surface area (BET) of the inorganic filler 1 is 18m2/g。
The rest is the same as embodiment 1, and the description is omitted here.
Example 3
The difference from example 1 is that: the inorganic filler 1 had a particle diameter D50 of 1.5 μm and a specific surface area (BET) of 18m2(ii) of/g.
The rest is the same as embodiment 1, and the description is omitted here.
Example 4
The difference from example 1 is that: the inorganic filler 1 had a particle diameter D50 of 1.2 μm and a specific surface area (BET) of 16m2(ii) of/g.
The rest is the same as embodiment 1, and the description is omitted here.
Example 5
The difference from example 1 is that: the inorganic filler 1 had a particle diameter D50 of 0.8. mu.m, and a specific surface area (BET) of 18m2(ii) of/g.
The rest is the same as embodiment 1, and the description is omitted here.
Example 6
The difference from example 1 is that: the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 88:1.5:2:6:5: 65.
The rest is the same as embodiment 1, and the description is omitted here.
Example 7
The difference from example 1 is that: the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 90:1:2:6:5: 65.
The rest is the same as embodiment 1, and the description is omitted here.
Example 8
The difference from example 1 is that: the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 78:1.5:2:6:5: 60.
The rest is the same as embodiment 1, and the description is omitted here.
Example 9
The difference from example 1 is that: the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 88:1.5:15:3:1: 50.
The rest is the same as embodiment 1, and the description is omitted here.
Example 10
The difference from example 1 is that: the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 95:4:3:8:15: 75.
The rest is the same as embodiment 1, and the description is omitted here.
Comparative example 1
(1) 80 parts of D50 are taken firstly and are 1 mu m, and the BET is 6.5m2Uniformly dispersing 55 parts of deionized water, 1.5 parts of a dispersing agent and 2 parts of a thickening agent for 30min at a high rotation speed of 2500rpm, and then obtaining a slurry dispersion liquid;
(2) placing the slurry dispersion liquid obtained in the step (1) in grinding equipment, controlling the flow at 1000L/h and the rotating speed at 750rpm, and grinding for 60min to obtain slurry grinding liquid;
(3) adding 6 parts of adhesive into the slurry grinding fluid obtained in the step (2), uniformly dispersing for 20min at the rotating speed of 1500rpm, adding 5 parts of modified PMMA microspheres, performing low-speed dispersion for 30min at 800rpm, and adding 0.1 part of wetting agent to obtain blended slurry;
(4) and (3) uniformly coating the blended slurry in the step (3) on two sides of a polyethylene microporous membrane, wherein the total thickness of the coating is 3 micrometers, and then drying in a drying oven at 50 ℃ to obtain the composite diaphragm.
Comparative example 2
(1) 80 parts of D50 are taken firstly and are 1 mu m, and the BET is 6.5m2Uniformly dispersing 55 parts of deionized water, 1.5 parts of a dispersing agent and 2 parts of a thickening agent for 30min at a high rotation speed of 2500rpm, and then obtaining a slurry dispersion liquid;
(2) placing the slurry dispersion liquid obtained in the step (1) in grinding equipment, controlling the flow at 1000L/h and the rotating speed at 750rpm, and grinding for 60min to obtain slurry grinding liquid;
(3) adding 6 parts of adhesive and 0.1 part of wetting agent into the slurry grinding fluid obtained in the step (2) to obtain conventional ceramic slurry, then uniformly coating the conventional ceramic slurry on one side of a polyethylene microporous membrane, wherein the thickness of the ceramic coating is 2 microns, and drying the conventional ceramic coating in an oven at 60 ℃ to obtain a conventional ceramic coating membrane;
(4) and (3) coating the conventional PMMA with the particle size D50 of 0.5 mu m on both sides of the conventional ceramic coating film in the step (1), wherein the total thickness of the PMMA coating is 1 mu m, and drying to obtain the composite diaphragm.
Comparative example 3
(1) 80 parts of D50 are taken firstly and have a particle size of 0.3 mu m and BET of 13m2Uniformly dispersing 1/g of inorganic filler, 55 parts of deionized water, 1.5 parts of dispersant and 2 parts of thickener for 30min at a high rotating speed of 2500rpm, and then obtaining slurry dispersion liquid;
(2) placing the slurry dispersion liquid obtained in the step (1) in grinding equipment, controlling the flow at 1000L/h and the rotating speed at 750rpm, and grinding for 60min to obtain slurry grinding liquid;
(3) adding 6 parts of adhesive into the slurry grinding fluid obtained in the step (2), uniformly dispersing at the rotating speed of 1500rpm for 20min, and then adding 0.1 part of wetting agent to obtain blended slurry;
(4) uniformly coating the blended slurry in the step (3) on one side of a polyethylene microporous membrane, wherein the total thickness of the coating is 2 microns, and then drying in a drying oven at 50 ℃ to obtain a coating diaphragm;
(5) and (3) coating the conventional PMMA with the particle size D50 of 0.5 mu m on both sides of the diaphragm 1 in the step (4), wherein the total thickness of the PMMA coating is 1 mu m, and drying to obtain the composite diaphragm.
And (3) performance testing: the composite separators prepared in the above examples 1 to 10 and comparative examples 1 to 3 were assembled into a cell by matching with the positive electrode sheet 3 and the negative electrode sheet 5 as shown in fig. 1, and the outer surface of the electrolyte was added to mount an aluminum plastic film casing to prepare a secondary battery for performance test, and the test results are recorded in table 1, and the secondary battery is exemplified by a lithium ion battery.
Testing the thermal shrinkage rate of the diaphragm: the separator prepared above was formed into a rectangular strip of 200 × 100mm (transverse × longitudinal), and then placed in an oven at 150 ℃ to be baked for 30min, and then taken out to test the transverse and longitudinal lengths, and the shrinkage was calculated.
The membrane interface adhesion testing method comprises the following steps: the method comprises the steps of disassembling a battery core of the lithium ion battery from an interface of an anode and a diaphragm in a drying room environment, standing for 5 minutes until an electrolyte is volatilized, cutting the interface of a cathode and the diaphragm with the size of 100mm multiplied by 25mm, and testing the interface of the cathode and the diaphragm by using a high-speed rail tensile machine (Shanghai research and lubrication optical technology Co., Ltd., TS-2000) and setting the tensile speed to be 5mm/min and the tensile displacement to be 50mm so as to perform interface peeling adhesion. From the following examples, 4 lithium ion batteries were taken for each group, and the average value of the adhesion of the negative electrode of the lithium ion battery to the interface of the separator was calculated.
And (3) testing the lithium precipitation area of the diaphragm interface: at 25 ℃, the lithium ion battery is charged to 4.45V at a constant current of 1C, then charged at a constant voltage until the current is 0.05C, and then discharged to 3.0V at a constant current of 1C, which is the first cycle. The lithium ion battery was cycled 400 times according to the above conditions. The lithium deposition area of the separator was obtained by the following method: taking a fully charged battery, disassembling to obtain a diaphragm, taking a high-power (more than 20 times) microscope to photograph, then analyzing different regions, abstracting the black region to be circular, and counting the lithium analysis region by utilizing gray difference to obtain the lithium analysis area.
Capacity retention rate test: charging the lithium ion secondary battery to 4.25V at a constant current of 2C at 25 ℃, then charging to 0.05C at a constant voltage of 4.25V, standing for 5min, and then discharging to 2.8V at a constant current of 2C, wherein the process is a charge-discharge cycle process, and the discharge capacity of the time is the discharge capacity of the first cycle. The lithium ion secondary battery was subjected to 400-cycle charge/discharge tests in accordance with the above-described method, and the discharge capacity per one cycle was recorded. The cycle capacity retention (%) was 400 cycles of discharge capacity/first cycle of discharge capacity × 100%.
TABLE 1
As shown in table 1, the composite separator prepared by the preparation method of the composite separator of the present invention has better heat resistance, adhesion, cycle performance, and service life, and less lithium deposition/black spots compared to the prior art.
As is apparent from the comparison of examples 1 to 5, when the inorganic filler 1D50 was set to 0.3. mu.m, the specific surface area (BET) was 13m2In the case of/g, the prepared composite diaphragm has better heat resistance, smaller heat shrinkage and higher dimensional stability. Compared with the examples 1 and 6-10, when the weight part ratio of the inorganic filler 1 to the dispersant to the thickener to the adhesive to the compression-resistant binder 2 to the solvent is 80:1.5:2:6:5:55, the prepared diaphragm has better performance, better adhesive force with a pole piece, less lithium/black spot separation area after multiple charge and discharge cycles and better capacity retention rate.
As can be seen from comparison of examples 1-10 and comparative examples 1-3, the addition of inorganic filler 1 having a higher BET and a small particle size can significantly reduce the thermal shrinkage of the separator at 150 ℃ and improve the safety of the battery;
by comparing the embodiment 1, the comparative example 2 and the comparative example 3, the PMMA microspheres with high compression ratio are added and adjusted to be in a coating structure mode of mixed coating, but the condition of black spots of a long-cycle interface is effectively improved, and the cycle capacity retention rate is improved.
Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
Claims (10)
1. The preparation method of the composite diaphragm is characterized by comprising the following steps:
step S1, adding the inorganic filler, the dispersant and the thickener into the solvent, mixing and dispersing, and grinding to obtain grinding fluid;
step S2, adding the adhesive into the grinding fluid, stirring and dispersing to obtain a premixed solution;
step S3, adding the compression-resistant binder into the pre-mixed liquid, stirring and dispersing to obtain blended slurry;
and step S4, coating the blended slurry on at least one surface of the base film, and drying to form a coating layer to obtain the composite diaphragm.
2. The preparation method of the composite diaphragm of claim 1, wherein the weight part ratio of the inorganic filler, the dispersing agent, the thickening agent, the adhesive, the compression-resistant binder and the solvent is 75-99: 0.1-3: 0.1-5: 1-10: 1-20: 50-80 parts.
3. The method for preparing the composite separator according to claim 1 or 2, wherein the step S3 is to add the compression-resistant binder to the pre-mixed liquid, stir and disperse the pre-mixed liquid, add 0.1 to 20 parts by weight of the wetting agent, mix and disperse the pre-mixed liquid to obtain the blended slurry.
4. The method for producing the composite separator according to claim 1 or 2, wherein the inorganic filler has a particle diameter D50 of 0.08 to 2 μm and a specific surface area of 10 to 100m2/g。
5. The method of manufacturing a composite separator according to claim 1 or 2, wherein the compression ratio of the compression-resistant adhesive is 30% to 80%.
6. The method of manufacturing a composite separator according to claim 5, wherein the compression resistant adhesive is polyacrylate-modified polymethyl methacrylate.
7. The method for manufacturing the composite separator according to claim 1 or 2, wherein the base film has a thickness of 3 to 20um, a porosity of 25 to 55%, and an air permeability of 70 to 200s/100 cc.
8. The method for producing a composite separator according to claim 1, wherein the inorganic filler comprises at least one of alumina, boehmite, magnesium hydroxide, aluminum hydroxide, magnesium oxide, calcium oxide, and silica; the dispersing agent comprises at least one of polyacrylic acid and sodium salt thereof, polyacrylamide, polyvinyl alcohol, sodium citrate, sodium ethylene diamine tetracetate, sodium diacetate, sodium hexametaphosphate and sodium silicate; the thickening agent comprises at least one of hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, sodium carboxymethyl cellulose, methyl cellulose and sodium alginate; the adhesive comprises a hydrophilic monomer, wherein the hydrophilic monomer comprises at least one of acrylic acid, methacrylic acid, acrylamide, vinyl alcohol and hydroxyethyl acrylate.
9. A composite separator produced by the method for producing a composite separator according to any one of claims 1 to 8.
10. A secondary battery comprising the composite separator of claim 9.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115483500A (en) * | 2022-09-21 | 2022-12-16 | 河北金力新能源科技股份有限公司 | High-circulation-rate diaphragm and preparation method thereof |
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