CN116154404A - Ceramic coating slurry for lithium battery diaphragm and preparation method thereof - Google Patents
Ceramic coating slurry for lithium battery diaphragm and preparation method thereof Download PDFInfo
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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
- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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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
- H01M50/431—Inorganic material
- H01M50/434—Ceramics
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- H—ELECTRICITY
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- 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
- H01M50/443—Particulate material
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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
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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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
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
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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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Abstract
The invention discloses ceramic coating slurry of a lithium battery diaphragm and a preparation method thereof, wherein the ceramic coating slurry comprises inorganic nano particles, a thickening agent, a microcapsule type binder and deionized water, the thickening agent is formed by compounding sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate, and the average particle size of the microcapsule type binder is larger than that of the inorganic nano particles; also relates to a preparation method of the ceramic coating slurry of the lithium battery diaphragm, which comprises the following steps: step one, adding the inorganic nano particles, a thickening agent and deionized water into a reaction vessel, and uniformly stirring to obtain mixed slurry; and step two, adding the microcapsule binder into the mixed slurry, and uniformly stirring to obtain the ceramic coating slurry of the lithium battery diaphragm. The technical scheme of the application has the effects of further improving the adhesive force of the ceramic coating to the base film and further improving the heat resistance and the foreign matter resistance of the whole diaphragm.
Description
Technical Field
The invention relates to the field of lithium batteries, in particular to ceramic coating slurry for a lithium battery diaphragm and a preparation method thereof.
Background
The separator used in the lithium ion battery at present is generally a polyolefin porous film, and because the polyolefin porous film has low melting point, when the temperature of the battery is increased, the polyolefin porous film is easy to shrink or melt to cause short circuit of the anode and the cathode, so that combustion explosion is caused. Therefore, in order to improve the thermal stability and mechanical strength of the separator, a ceramic coating is generally coated on the separator.
In the prior art, inorganic ceramic particles and a binder are mixed into slurry, and then the slurry is coated on a diaphragm to form a ceramic coating. Although foreign matter resistance, heat resistance and the like of the diaphragm are greatly improved compared with those of the base film after the diaphragm is coated with a layer of ceramic coating, the adhesion between the ceramic coating and the pole piece is extremely low, and the diaphragm and the pole piece can be separated possibly, so that the safety problem exists.
For this case, it is common to apply an adhesive on the ceramic coating after the ceramic coating is applied to the separator, so as to bond the separator and the pole piece, but this way increases the complexity of the process, and an additional adhesive layer is required, so there is room for improvement.
Disclosure of Invention
In order to further improve the bonding performance of the separator and the electrode and avoid the need of additional coating of an adhesive, the application provides ceramic coating slurry of a lithium battery separator and a preparation method thereof. According to the mass ratio of sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate (5-15): (10-20): (1-10): the thickening agent compounded in the proportion of (1-10) can improve the viscosity of the ceramic coating slurry when standing, can improve the fluidity of the coating slurry when stirring, can further promote the uniform distribution of the microcapsule binder in the ceramic coating slurry, and can further improve the adhesive force of the ceramic coating slurry to the diaphragm.
In a first aspect, the application provides a ceramic coating slurry for a lithium battery separator, which adopts the following technical scheme:
the ceramic coating slurry for the lithium battery diaphragm comprises, by mass, 60-70 parts of inorganic nanoparticles, 2-5.5 parts of a thickener, 5-10 parts of a microcapsule type binder and 50-60 parts of deionized water, wherein the thickener comprises sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate salt and sodium silicate according to the mass ratio of (5-15): (10-20): (1-10): the ratio of (1-10), wherein the average particle diameter of the microcapsule binder is larger than the average particle diameter of the inorganic nanoparticles.
According to the technical scheme, the average grain size of the microcapsule type binder is larger than that of the inorganic nano-particles, so that when the ceramic coating slurry is coated on the base film, the microcapsule type binder protrudes out of the surfaces of other components, before the ceramic coating slurry is completely dried, the lithium battery pole piece and the diaphragm are pressed together, the microcapsule is broken, the binder in the microcapsule is released, the binder is uniformly adhered to the ceramic coating and the pole piece under the pressing together of the battery pole piece and the diaphragm, and the step of smearing a layer of binder on the ceramic coating is omitted, so that the operation is more convenient, and meanwhile, the adhesive stability of the diaphragm and the pole piece and the adhesive of the ceramic coating and the base film are improved. The adhesive has good lithium electron passing property because of its own property, and the microcapsule adhesive can maximally utilize the adhesive effect of the adhesive, reduce the unnecessary addition and use of the adhesive, and better improve the passing performance of lithium electrons of the diaphragm.
According to the technical scheme, the ceramic coating slurry containing sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate can maintain the fluidity required by coating during stirring, can promote the homogenization of the ceramic coating slurry, obviously reduces the addition amount of deionized water in the ceramic coating slurry, and reduces the probability of unstable adhesion of ceramic particles and a base film of a diaphragm due to high fluidity of the deionized water; the ceramic coating slurry has the advantages that the viscosity of the ceramic coating slurry can be increased when the ceramic coating slurry is kept still, the suspension stability of solids in the ceramic coating slurry can be improved, ceramic particles can be coated on a base film of a diaphragm more easily and uniformly when the ceramic coating slurry is coated, and when the coating is finished, the adhesive force of the ceramic coating slurry to the base film of the diaphragm is increased, so that the ceramic coating slurry cannot fall off or shift when being naturally attached to the base film, the probability that the subsequent ceramic particles fall off from the base film is reduced, and the integral heat resistance and foreign matter resistance of the diaphragm are further improved.
The microcapsule type adhesive can be uniformly distributed in the ceramic coating slurry through the thickener, and the viscosity of the ceramic coating slurry when standing can be remarkably improved due to sodium carboxymethyl cellulose, polyethylene oxide, polycarboxylic acid ammonium salt and sodium silicate, so that the stability of the microcapsule type adhesive in the ceramic coating slurry is further improved, the deposition of the microcapsule type adhesive in the ceramic coating slurry is reduced, and when the ceramic coating slurry is coated on a base film, the microcapsule type adhesive can be stably attached to the base film and cannot shift due to the high viscosity of the ceramic coating slurry, so that the adhesion between a diaphragm and a pole piece is further improved.
Preferably, the microcapsule type binder comprises a capsule shell and a capsule core, and the capsule shell is chitosan.
In the technical scheme, the capsule shell is chitosan, amino and ether oxygen groups exist in the chitosan molecule and can be complexed with lithium ions, the chitosan cannot obstruct the penetration of the lithium ions, and the chitosan serving as the capsule shell material of the microcapsule cannot influence the integral lithium ion penetration performance of the diaphragm.
Preferably, the core is a sodium hexametaphosphate binder.
In the technical scheme, the sodium hexametaphosphate is used as the binder, has excellent high temperature resistance and stability, can promote the polymerization of ceramic particles, can absorb redundant deionized water in ceramic coating slurry, can better adhere to a base film, and can also improve the adhesion of the ceramic coating and a pole piece.
The sodium hexametaphosphate binder is wrapped in the chitosan, so that the contact and polymerization reaction of the sodium hexametaphosphate and the inorganic nano particles in the ceramic coating slurry are avoided, after the inorganic nano particles and the microcapsule binder are uniformly distributed on the base film of the diaphragm, the microcapsule is crushed by clicking the lamination of the pole piece and the diaphragm to release the binder, the binder and the inorganic nano particles react, the thickness uniformity of the ceramic coating is further improved, the distribution average degree of the inorganic nano particles on the base film of the diaphragm is improved, the adhesion of the inorganic nano particles and the diaphragm is promoted, the adhesion of the electrode pole piece and the diaphragm is promoted, the heat resistance agent of the diaphragm is further improved, and the influence of the ceramic coating on the penetrability of lithium ions is reduced.
Preferably, the core-shell ratio of the microcapsule binder is 1: (1-2).
In the above technical solution, the core-shell ratio of the defined microcapsule binder is 1: (1-2), the microcapsule type adhesive is easier to be crushed when the pole piece is covered, so that the probability that the microcapsule type adhesive cannot be crushed due to the fact that the capsule shell is over is reduced. The adhesive wrapped in the microcapsule type adhesive can be better utilized, so that the diaphragm and the pole piece can be firmly adhered.
Preferably, the mass ratio of the sodium carboxymethyl cellulose to the polyethylene oxide to the ammonium salt of the polycarboxylic acid to the sodium silicate is as follows: 4:7:2:2.
in the technical scheme, the thickener according to the mass ratio can better improve the adhesive force of the ceramic coating slurry, the ceramic coating slurry can be better adhered to the base film of the diaphragm, and the heat resistance and the foreign matter resistance of the base film of the lithium battery are improved.
Preferably, the mass ratio of the inorganic nano particles, the thickener, the microcapsule type binder and the deionized water is as follows: 70:3:8:50.
according to the technical scheme, the ceramic coating slurry prepared according to the mass ratio has better viscosity in a static state, suspended particles in the slurry can be more stably and uniformly dispersed in the slurry, the deposition of the suspended particles in the slurry is further reduced, meanwhile, the ceramic coating slurry has better fluidity during stirring, and the ceramic coating slurry can be more easily and uniformly adhered to the base film of the diaphragm.
Preferably, the average particle diameter of the inorganic nanoparticles is 100 to 500nm, and the average particle diameter of the microcapsule binder is 1 to 10 μm.
In the technical scheme, the inorganic nano particles and the microcapsule type binder with the particle size are limited, so that the fluidity and the adhesive force of the ceramic coating slurry can be further promoted.
Preferably, the preparation method of the microcapsule type binder comprises the following steps:
(1) The mass ratio is 1: dissolving the sodium hexametaphosphate and the chitosan in the (1-2) in 2wt% acetic acid solution to prepare a chitosan acetic acid solution of the sodium hexametaphosphate;
(2) Dropwise adding the chitosan acetic acid solution of sodium hexametaphosphate into liquid paraffin containing an emulsifier, wherein the temperature is 40-60 ℃, the fixed revolution speed is 2000-2500 rpm, and stirring and emulsifying for 15-20 min to obtain a mixed solution A;
(3) Regulating the pH value of the mixed solution A to 5-6, and adding a crosslinking curing agent to cure for two hours to obtain a mixed solution B;
(4) And (3) centrifugally separating the mixed solution B, washing and drying to obtain the microcapsule type adhesive.
According to the technical scheme, the microcapsule type binder prepared by the method of emulsifying the solution, adjusting the pH value and adding the crosslinking curing agent is more uniform in particle size and better in coating property.
Preferably, the mixed solution A in step 3 in the preparation method of the microcapsule binder is adjusted to pH 5.
In the technical scheme, the pH value of the solution A in the step 3 is adjusted to 5, so that the prepared capsule type adhesive has a more stable structure and is less prone to damage.
In a second aspect, the preparation method of the ceramic coating slurry for the lithium battery diaphragm provided by the application adopts the following technical scheme:
the preparation method of the ceramic coating slurry of the lithium battery diaphragm comprises the following steps:
(1) Adding the inorganic nano particles, the thickener and the deionized water into a reaction vessel, wherein the temperature range is 40-60 ℃, the stirring speed is 180-250 rpm, and stirring is carried out for 1-2 h to obtain mixed slurry;
(2) And adding the microcapsule type binder into the mixed slurry, wherein the temperature range is 40-60 ℃, the stirring speed is 180-250 rpm, and the stirring is carried out for 1-2 hours, so as to obtain the ceramic coating slurry of the lithium battery diaphragm.
In the technical scheme, other components except the microcapsule type adhesive are uniformly mixed, so that the situation that the capsule shell is broken in advance due to huge friction between the microcapsule type adhesive and inorganic nano particles during pouring is prevented, and the probability of breakage of the microcapsule type adhesive during stirring can be reduced to the greatest extent by adding the components in two steps for stirring.
Wherein the inorganic nano particles are one or a mixture of more than two of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, magnesium oxide, zinc oxide, barium oxide and calcium carbonate in any proportion.
In summary, the present application includes at least one of the following beneficial technical effects:
1. the average grain diameter of the microcapsule type binder is larger than that of the inorganic nano-particles, so that when the ceramic coating slurry is coated on the base film, the microcapsule type binder protrudes out of the surfaces of other components, when the ceramic coating slurry is not dried, the lithium battery pole piece and the diaphragm are pressed together, the microcapsule is broken, the binder in the microcapsule is released, the binder is uniformly adhered to the ceramic coating and the pole piece under the pressing together of the battery pole piece and the diaphragm, the adhesion stability of the diaphragm and the pole piece is improved, and meanwhile, the adhesion between the ceramic coating and the base film is also improved. The adhesive has good lithium electron passing property because of its own property, and the microcapsule adhesive can maximally utilize the adhesive effect of the adhesive, reduce the unnecessary addition and use of the adhesive, and better improve the passing performance of lithium electrons of the diaphragm.
2. The ceramic coating slurry containing sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate can maintain the fluidity required by coating during stirring, can promote the homogenization of the ceramic coating slurry, obviously reduce the addition amount of deionized water in the ceramic coating slurry, and reduce the probability of unstable adhesion of ceramic particles and a base film of a diaphragm caused by high fluidity of the deionized water; the ceramic coating slurry has the advantages that the viscosity of the ceramic coating slurry can be increased when the ceramic coating slurry is kept still, the suspension stability of solids in the ceramic coating slurry can be improved, ceramic particles can be coated on a base film of a diaphragm more easily and uniformly when the ceramic coating slurry is coated, and when the coating is finished, the adhesive force of the ceramic coating slurry to the base film of the diaphragm is increased, so that the ceramic coating slurry cannot fall off or shift when being naturally attached to the base film, the probability that the subsequent ceramic particles fall off from the base film is reduced, and the integral heat resistance and foreign matter resistance of the diaphragm are further improved.
3. The sodium hexametaphosphate binder is wrapped in the chitosan, so that the contact and polymerization reaction of the sodium hexametaphosphate and the inorganic nano particles in the ceramic coating slurry are avoided, after the inorganic nano particles and the microcapsule binder are uniformly distributed on the base film of the diaphragm, the microcapsule is crushed by clicking the lamination of the pole piece and the diaphragm to release the binder, the binder and the inorganic nano particles react, the thickness uniformity of the ceramic coating is further improved, the distribution average degree of the inorganic nano particles on the base film of the diaphragm is improved, the adhesion of the inorganic nano particles and the diaphragm is promoted, the adhesion of the electrode pole piece and the diaphragm is promoted, the heat resistance agent of the diaphragm is further improved, and the influence of the ceramic coating on the penetrability of lithium ions is reduced.
Detailed Description
A ceramic coating paste for a lithium battery separator and a method of preparing the same will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
Examples 1 to 3
Ceramic coating slurries for lithium battery separators, wherein the amounts of the components are shown in Table 1.
TABLE 1 amounts of ingredients to be added in examples 1 to 3
Wherein, preparation of the ceramic coating slurries of examples 1-3:
step 01) adding inorganic nano particles (the average particle size is 100-500 nm), sodium carboxymethyl cellulose, polyethylene oxide, ammonium salt of polycarboxylic acid, sodium silicate and deionized water into a reaction vessel, and stirring at 200r/min for 1.5h at 50 ℃ to obtain mixed slurry.
Step 02) adding the microcapsule binder into the mixed slurry, and stirring at 50 ℃ for 1h at 200r/min to obtain the ceramic coating slurry.
Wherein, preparation of the microcapsule type adhesive of examples 1-3:
step 1) sodium metaphosphate and chitosan with the mass ratio of 1:2 are dissolved in acetic acid solution with the weight percent of 2 to prepare chitosan acetic acid solution of sodium metaphosphate with the chitosan content of 2 weight percent; preparing liquid paraffin containing span-80 from the liquid paraffin and span-80 in a volume ratio of 24:1; mechanically stirring liquid paraffin containing span-80 at 200rpm/min at 50 ℃ and dropwise adding chitosan acetic acid solution of sodium metaphosphate to obtain a first mixed solution.
Step 2) adding sodium hydroxide solution (1 mol/L) into the first mixed solution dropwise, adjusting the pH value of the first mixed solution to be 5, and stirring and emulsifying for 15min at 50 ℃ at a fixed rotation speed of 2500rpm to obtain a second mixed solution.
And 3) adding glutaraldehyde into the second mixed solution, and curing for two hours at 50 ℃ to obtain a third mixed solution.
And 4) taking the solid of the third mixed solution after centrifugal separation, washing the solid with petroleum ether, acetone and deionized water in sequence, and vacuum drying at 30 ℃ for 48 hours to prepare the microcapsule binder.
Example 4
In the process of step 01, the amount of sodium carboxymethyl cellulose added was 0.8kg, the amount of polyethylene oxide added was 1.4kg, the amount of ammonium polycarboxylate salt added was 0.4kg, and the amount of sodium silicate added was 0.4kg, unlike in example 3.
Example 5
In contrast to example 3, the microcapsule binder was prepared by dissolving sodium metaphosphate and chitosan in a mass ratio of 1:1 in 2wt% acetic acid solution in step 1 to prepare a chitosan acetic acid solution of sodium metaphosphate having a chitosan content of 2 wt%.
Example 6
In the case of the preparation of the microcapsule type adhesive, a sodium hydroxide solution (1 mol/L) was added dropwise to the first mixed solution in step 2 to adjust the pH of the first mixed solution to 6, unlike in example 3.
Comparative example 1
Unlike example 3, the ceramic coating slurry was prepared, and sodium carboxymethyl cellulose was replaced with hydroxyethyl cellulose in equal amount in step 01.
Comparative example 2
Unlike example 3, the ceramic coating slurry was prepared, and in step 01, polyethylene oxide was replaced with hydroxyethylcellulose in equal amounts.
Comparative example 3
Unlike example 3, the ceramic coating slurry was prepared, and in step 01, the ammonium polycarboxylate salt was replaced with hydroxyethylcellulose in equal amounts.
Comparative example 4
Unlike example 3, the ceramic coating slurry was prepared, and in step 01, sodium silicate was replaced with calcium silicate in equal amounts.
Comparative example 5
Unlike example 3, the ceramic coating slurry was prepared, and deionized water was added in an amount of 70 parts in step 01.
Comparative example 6
Unlike example 3, the preparation of the microcapsule-type binder was omitted, and the microcapsule-type binder was replaced with sodium hexametaphosphate in the same amount in the preparation of the ceramic coating slurry, and the preparation method of the ceramic coating slurry was changed to:
inorganic nano particles (the average particle size is 100-500 nm), sodium carboxymethyl cellulose, polyethylene oxide, ammonium salt of polycarboxylic acid, sodium silicate, sodium hexametaphosphate and deionized water are added into a reaction vessel, and stirred for 1.5 hours at the temperature of 50 ℃ at the speed of 200r/min, so as to obtain ceramic coating slurry.
Experiment 1
And observing the distribution condition of the microcapsule adhesive in the coating process of the ceramic coating slurry by using a laser resonance electron microscope.
The experimental method comprises the following steps: the ceramic coating slurries of the above examples and comparative examples were coated on a transparent film cloth by a coater, and after the ceramic coating slurry was dried, the film cloth was cut into 70 mm-30 mm squares, and the squares were placed under a laser resonance electron microscope (FV 3000) to observe the distribution of the microcapsule type binder.
Experimental results: by observation, the microcapsule-type binders of examples 1 to 6 were uniformly distributed, and the microcapsule-type binders in the ceramic coating slurries of comparative examples 1 to 5 were partially bonded together, and the distribution gaps between the microcapsule-type binders were uneven.
Experiment 2
Internal friction is generated between molecules when the slurry flows, and the property is called the viscosity of liquid, the viscosity is expressed as viscosity, the viscosity can be used for representing the fluidity of the slurry, and the fluidity of the ceramic coating slurry during stirring is judged by testing the viscosity of the ceramic coating slurry.
The experimental method comprises the following steps: the viscosity was measured using an NDJ-9S viscometer (Shanghai Fang Rui instruments). Pouring the ceramic coating slurries of each experimental example and comparative example into a beaker respectively, selecting a No. 1 rotor of an NDJ-9S type viscometer for viscosity measurement, ensuring that the liquid level of the ceramic coating slurry is aligned with the scales of the rotor in the measurement process, and reading the viscosity value after the ceramic coating slurry is stable. The experimental results are shown in Table 2.
TABLE 2 viscosity values of ceramic coating slurries
Experimental data show that the viscosity of the ceramic coating slurry added with sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate is only slightly higher than that of the ceramic coating slurry added with a large amount of deionized water when the ceramic coating slurry is stirred, namely, under the condition that the addition amount of the deionized water is obviously reduced, the compounding of sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate still can maintain good fluidity of the ceramic coating slurry when stirring, the microcapsule type binder and the inorganic nano particles can be uniformly dispersed in the ceramic coating slurry, the influence of the deionized water can be reduced when preparing the ceramic coating of the lithium battery diaphragm, and the microcapsule type binder and the inorganic nano particles can be more uniformly coated on the base film of the battery diaphragm, so that the performance of the lithium battery is further improved.
Experiment 3
Sagging experiments the fluidity of the ceramic coating slurry was tested both when stirred and when left to stand.
The experimental method comprises the following steps: a 200 x 200mm glass plate with a smooth and flat surface is taken, placed on a flat tabletop, and is inclined at an angle of 30 degrees with respect to the tabletop, and a titration line is marked at a position 10mm away from the top end of the glass plate.
The ceramic coating slurries of the examples and comparative examples were taken 1ml with a graduated disposable Pasteur pipette (size 1 ml) and completely dropped onto the titration line from a height of 2mm from the titration line of a clean glass plate within 1S, and the flow distance S1 within 30S of the ceramic coating slurry was measured.
1ml of each of the ceramic coating slurries of the examples and comparative examples under stirring was taken with a graduated disposable Pasteur pipette (size 1 ml), and the ceramic coating slurry was completely dropped onto the titration line from a height of 2mm from the titration line of the clean glass plate within 1S, and the flow distance S2 within 30S of the ceramic coating slurry was measured.
The experimental results are shown in Table 3
TABLE 3 fluidity of ceramic coating slurries
| Group of | S1/mm | S2/mm |
| Experimental example 1 | 23 | 59 |
| Experimental example 2 | 25 | 61 |
| Experimental example 3 | 21 | 53 |
| Experimental example 4 | 17 | 49 |
| Experimental example 5 | 28 | 60 |
| Experimental example 6 | 26 | 53 |
| Comparative example 1 | 36 | 38 |
| Comparative example 2 | 31 | 32 |
| Comparative example 3 | 35 | 37 |
| Comparative example 4 | 38 | 40 |
| Comparative example 5 | 63 | 65 |
| Comparative example 6 | 25 | 24 |
Experimental data show that the ceramic coating slurry added with sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate has increased viscosity when being stood, can improve the suspension stability of solids in the ceramic coating slurry, has increased fluidity when being stirred, can maintain the fluidity required by coating, and obviously reduces the addition amount of deionized water in the ceramic coating slurry.
Experiment 4
And a microcomputer controlled electronic universal tester (universal testing machine) is adopted to test the peeling strength of the diaphragm and the pole piece through a 180-degree peeling test, so that the adhesion between the diaphragm and the pole piece is tested.
The experimental method comprises the following steps:
adhesion of lithium battery separator and pole piece:
and coating the ceramic coating slurries of the embodiments and the comparative examples on the base film of the lithium battery diaphragm by a coating machine, pressing the pole piece of the lithium battery and the base film of the lithium battery diaphragm by a roller press when the ceramic coating slurries are not dried, and finally vacuum-drying the ceramic coating slurries of the base film of the diaphragm and the pole piece, which are adhered with the lithium battery, at 30 ℃ for 48 hours, so that the lithium battery diaphragm and the pole piece are adhered.
Test of peel strength:
the test temperature is 25 ℃ and the relative humidity is 50%, the diaphragms adhered with pole pieces are cut into 80mm x 25mm, one face with the pole pieces is bent inwards for 180 degrees, the pole pieces are peeled off from the diaphragms by about 1mm, the pole pieces and the diaphragms are respectively fixed on an upper holder and a lower holder, the sensors are just not stressed, a microcomputer control electronic universal tester is started, 180 degrees peeling force test items are selected, the peeling speed is set to be 100mm/min, and the test is started. Each of the above examples and comparative examples was tested 3 times, the test results were averaged, and the peel strength (N/m) of the separator and the pole piece were tested, and the test results are shown in table 4.
TABLE 4 determination of peel strength of separator and pole piece
| Peel strength (N/m) | |
| Experimental example 1 | 121 |
| Experimental example 2 | 124 |
| Experimental example 3 | 123 |
| Experimental example 4 | 128 |
| Experimental example 5 | 118 |
| Experimental example 6 | 114 |
| Comparative example 1 | 66 |
| Comparative example 2 | 69 |
| Comparative example 3 | 58 |
| Comparative example 4 | 86 |
| Comparative example 5 | 85 |
| Comparative example 6 | 109 |
Experimental data show that the ceramic coating slurry containing sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate can remarkably improve the homogeneity of the microcapsule type adhesive in the ceramic coating slurry, so that the microcapsule type adhesive can be uniformly coated on a base film of a diaphragm, when the diaphragm and a pole piece are adhered, the adhesive in a capsule core can be uniformly dispersed between the diaphragm and the pole piece after the microcapsule type adhesive is broken, the adhesive force between the diaphragm and the pole piece is better, the condition that the ceramic coating falls is reduced, and the lithium battery is safer and more stable in operation.
Experiment 5
The safety of batteries using ceramic coating slurries was determined using weight impact and needling experiments. The heavy object impact simulates that an external heavy object freely falls to the surface of the battery from a high position, the inside of the battery is extruded instantly by gravity reuse, and whether the battery can keep safety or not is inspected if the diaphragm can not effectively block the anode and the cathode at the moment. The needling test is performed by inserting nails into the battery and piercing the housing, causing a short circuit between adjacent pole pieces and contact of the electrolyte with air.
The experimental method comprises the following steps:
preparation of ceramic coating of lithium battery separator:
and coating the ceramic coating slurry on the base film of the lithium battery diaphragm by a coating machine, pressing the pole piece of the lithium battery and the base film of the lithium battery diaphragm by a roller press when the ceramic coating slurry is not dried, and finally vacuum drying the ceramic coating slurry of the base film of the diaphragm and the pole piece of the lithium battery at 30 ℃ for 48 hours, wherein the lithium battery diaphragm and the pole piece are adhered.
All prepared lithium battery diaphragms and pole pieces of experimental examples and comparative examples are assembled into a lithium battery by adopting the same method, and the lithium battery is fully charged.
Weight impact: the battery in a full-charge state is placed at the bottom of the impact device, a round bar with the diameter of 16mm is placed on the surface of the battery core, then a weight of 10kg freely falls from the height, the battery is impacted in the front, whether the battery is ignited or not is observed, and the result is recorded.
Needling: the center of the fully charged battery was punched with a stainless steel tip having a diameter of 3mm, held for 1 hour, and whether the battery exploded by fire was observed, and the result was recorded.
The experimental results are shown in Table 5
TABLE 5 weight impact and needling test results
| Heavy object impact | Needling process | |
| Experimental example 1 | No fire or explosion | No fire or explosion |
| Experimental example 2 | Does not get on fireNot exploding | No fire or explosion |
| Experimental example 3 | No fire or explosion | No fire or explosion |
| Experimental example 4 | No fire or explosion | No fire or explosion |
| Experimental example 5 | No fire or explosion | No fire or explosion |
| Experimental example 6 | No fire or explosion | No fire or explosion |
| Comparative example 1 | Firing on fire | Firing on fire |
| Comparative example 2 | Firing on fire | Firing on fire |
| Comparative example 3 | Firing on fire | Firing on fire |
| Comparative example 4 | Firing on fire | Firing on fire |
| Comparative example 5 | Smoking device | Smoking device |
| Comparative example 6 | Smoking device | Smoking device |
Experimental data show that the ceramic coating prepared by adding the ceramic coating slurry of sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate and sodium silicate has the effect of better improving the stability of the diaphragm, and can further improve the safety of the lithium battery.
The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.
Claims (10)
1. The ceramic coating slurry for the lithium battery diaphragm is characterized by comprising, by mass, 60-70 parts of inorganic nanoparticles, 2-5.5 parts of a thickener, 5-10 parts of a microcapsule type binder and 50-60 parts of deionized water, wherein the thickener comprises sodium carboxymethyl cellulose, polyethylene oxide, ammonium polycarboxylate salt and sodium silicate according to the mass ratio of (5-15): (10-20): (1-10): and (1-10), wherein the average particle size of the microcapsule binder is larger than that of the inorganic nano particles.
2. The ceramic coating paste of a lithium battery separator according to claim 1, wherein the microcapsule type binder comprises a capsule shell and a capsule core, and the capsule shell is chitosan.
3. The ceramic coating slurry of a lithium battery separator of claim 2, wherein the capsule core is a sodium hexametaphosphate binder.
4. A ceramic coating paste for lithium battery separator according to claim 3, wherein the core-shell ratio of the microcapsule binder is 1: (1-2).
5. The ceramic coating slurry of the lithium battery diaphragm, according to claim 1, wherein the mass ratio of the sodium carboxymethyl cellulose to the polyethylene oxide to the ammonium polycarboxylate salt to the sodium silicate is as follows: 4:7:2:2.
6. the ceramic coating slurry of the lithium battery separator according to claim 5, wherein the mass ratio of the inorganic nano particles, the thickener, the microcapsule type binder and the deionized water is as follows: 70:3:8:50.
7. the ceramic coating slurry for lithium battery separator according to claim 1, wherein the average particle size of the inorganic nanoparticles is 100-500 nm, and the average particle size of the microcapsule binder is 1-10 μm.
8. A ceramic coating paste for lithium battery separator according to claim 3, wherein the preparation method of the microcapsule type binder comprises the following steps:
(1) Dissolving sodium hexametaphosphate and chitosan with the mass ratio of 1 (1-2) in acetic acid solution with the weight percentage of 2 to prepare chitosan acetic acid solution of sodium hexametaphosphate;
(2) Dropwise adding the chitosan acetic acid solution of sodium hexametaphosphate into liquid paraffin containing an emulsifier, wherein the temperature is 40-60 ℃, the fixed revolution speed is 2000-2500 rpm, and stirring and emulsifying for 15-20 min to obtain a mixed solution A;
(3) Adjusting the pH value of the mixed solution A to 5-6, and adding a crosslinking curing agent to cure for two hours to obtain a mixed solution B;
(4) And (3) centrifugally separating the mixed solution B, washing and drying to obtain the microcapsule type adhesive.
9. The ceramic coating of a lithium battery separator according to claim 8, wherein the mixed solution a in step 3 of the preparation method of the microcapsule binder is adjusted to pH 5.
10. A method for preparing the ceramic coating slurry of the lithium battery separator according to any one of claims 1 to 9, comprising the steps of:
(1) Adding the inorganic nano particles, the thickener and the deionized water into a reaction vessel, wherein the temperature range is 40-60 ℃, the stirring speed is 180-250 rpm, and stirring is carried out for 1-2 hours to obtain mixed slurry;
(2) And adding the microcapsule type binder into the mixed slurry, wherein the temperature range is 40-60 ℃, the stirring speed is 180-250 rpm, and the stirring is carried out for 1-2 hours, so as to obtain the ceramic coating slurry of the lithium battery diaphragm.
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| CN116742278B (en) * | 2023-08-14 | 2023-10-24 | 中材锂膜(宜宾)有限公司 | Separator, preparation method thereof, electrochemical cell using separator and electricity utilization device |
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