CN115084779A - Composite modified slurry, modified ceramic-based composite membrane and preparation method - Google Patents

Composite modified slurry, modified ceramic-based composite membrane and preparation method Download PDF

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CN115084779A
CN115084779A CN202210666333.2A CN202210666333A CN115084779A CN 115084779 A CN115084779 A CN 115084779A CN 202210666333 A CN202210666333 A CN 202210666333A CN 115084779 A CN115084779 A CN 115084779A
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llzto
powder
modified
peo
acetic acid
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母静波
徐锋
苏碧海
石琳琳
李峰
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Hebei Gellec New Energy Material Science and Technoloy Co Ltd
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Hebei Gellec New Energy Material Science and Technoloy Co Ltd
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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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/12—Chemical modification
    • 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
    • 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
    • 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
    • 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
    • H01M50/426—Fluorocarbon polymers
    • 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
    • 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
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • 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
    • 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
    • H01M50/497—Ionic conductivity
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/06—Polyethene
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    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C08J2323/12—Polypropene
    • 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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Abstract

The invention relates to a composite modified slurry for modifying a battery diaphragm, which comprises the following components in percentage by weight: polyethylene oxide electrolyte film-forming material, mixed slurry of glacial acetic acid and LLZTO powder and binder PVDF; the polyethylene oxide electrolyte film-forming material is PEO-LiTFSI or PEO-LiFSI, and the molar ratio of PEO to Li is 6-10: 1; in the mixed slurry of glacial acetic acid and LLZTO powder, the solvent is DMF, and the LLZTO powder is Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (ii) a Glacial acetic acid accounts for 8-12% of the mass of the LLZTO powder, and DMF accounts for 8-12% of the mass of the LLZTO powder; wherein the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the binder PVDF is 45-55: 36-44: 8-12. And (3) dipping the base membrane to be modified such as a PE diaphragm or a PP diaphragm on the two sides by adopting a pulling method, taking out, and drying to obtain the modified diaphragm. Through testing, the thermal stability, mechanical property, electrochemical property, interface stability and other properties of the modified diaphragm are obviously improved.

Description

Composite modified slurry, modified ceramic-based composite membrane and preparation method
Technical Field
The invention relates to the technical field of new energy batteries, in particular to a composite modified slurry for a modified battery diaphragm, a modified ceramic matrix composite membrane and a preparation method thereof.
Background
In the construction of lithium batteries, the separator is one of the key internal components. The separator has a main function of separating the positive electrode and the negative electrode of the battery to prevent short circuit due to contact between the two electrodes, and also has a function of allowing electrolyte ions to pass therethrough. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The battery is different in kind and the separator used is different. The commercially available separator materials are mainly Polyethylene (PE) and polypropylene (PP) based polyolefin (polyethylene) separators. However, the pure PE or PP separator has poor mechanical strength (especially tensile strength) and thermal stability, which limits the environmental temperature suitable for application, and the pure PE or PP separator has poor mechanical strength, and after many cycles of the battery, lithium dendrites are easily formed on the surface of the pure PE or PP separator, which causes the separator to form puncture holes. These factors all seriously affect the cycle performance, cycle capacity retention rate, and safety of the battery.
In order to improve the performance of pure PE or PP diaphragms, a plurality of technical reports of diaphragm materials with PE or PP + ceramic coatings have appeared nowadays, namely PE or PP diaphragms are modified by utilizing the characteristics of high temperature resistance, high mechanical strength and the like of the ceramic coatings. For example, Huxu Yao, Shangyoming et al, 2013, disclosed an article entitled "Nano silica/polyimide coated modified Polypropylene diaphragm" and disclosed the use of SiO 2 Inert filler modified PP membranes by close-packed SiO 2 The nano particles are mutually overlapped on the surface of the membrane to form a rigid supporting layer, so that the modified PP membrane has good heat-resistant shrinkage performance, but whether the tensile strength of the modified membrane is obviously improved or not is not clear. CN110459803A describes the use of inorganic ceramic electrolyte LLZTO, polymer electrolyte modified PEO and PPO copolymer, and lithium salt LiClo 4 And acetonitrile to obtain the organic-inorganic electrolyte slurry. Filling the organic-inorganic electrolyte slurry into the composite substrate in a mode of repeated pressurization pouring and repeated drying, filling the organic-inorganic electrolyte slurry into pores of the composite substrate, carrying out hot pressing to obtain a modified composite electrolyte membrane with the density of 95%, and testing the density of the composite electrolyte membrane to be 1.5 x 10 -4 S/cm. The scheme is complex to operate, the PE diaphragm substrate needs to be filled in a mode of repeated pressure pouring, repeated drying and hot pressing, the adhesion of the introduced LLZTO on the surface of the substrate film is poor, and the LLZTO is easy to fall off from a pole piece in the long-time working process of the battery; meanwhile, the composite electrolyte membrane has low ionic conductivity, and when the composite electrolyte membrane is used for a solid electrolyte membrane, the composite electrolyte membrane has high internal resistance, low integral rate performance and high voltage drop during high-rate discharge.
In summary, the performance of the existing separator has many disadvantages, and there is a need to provide an improved solution to improve the performance of the existing separator or composite electrolyte membrane.
Disclosure of Invention
Technical problem to be solved
In view of the above-mentioned drawbacks and disadvantages of the prior art, the present invention provides a composite modified slurry for a modified battery separator, a modified ceramic-based composite membrane having high thermal stability, high ionic conductivity, and excellent mechanical strength, and having good interface stability with an electrode, and a method for preparing the same. In addition, the preparation method provided by the invention has the advantages of simple operation method, low cost, environmental protection, good repeatability, easiness for large-scale batch production and the like.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
in a first aspect, the present invention provides a composite modified slurry for modifying a battery separator, comprising: polyethylene oxide electrolyte film-forming material, mixed slurry of glacial acetic acid and LLZTO powder and binder PVDF;
wherein the polyethylene oxide electrolyte film-forming material is PEO-LiTFSI or PEO-LiFSI, and the molar ratio of PEO to Li is 6-10: 1;
mixing glacial acetic acid with LLZTO powder in the presence of DMF as solvent, and Li as LLZTO powder 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (ii) a Glacial acetic acid accounts for 8-12% of the mass of the LLZTO powder, and DMF accounts for 8-12% of the mass of the LLZTO powder;
wherein the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the binder PVDF is 45-55: 36-44: 8-12.
Preferably, the polyethylene oxide electrolyte film-forming material is PEO-LiTFSI, and wherein the molar ratio of PEO to Li is 8: 1.
preferably, in the mixed slurry of glacial acetic acid and LLZTO powder, the glacial acetic acid accounts for 10% of the mass of the LLZTO powder, and the amount of DMF accounts for 10% of the mass of the LLZTO powder.
Preferably, in the composite modified slurry, the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the binder PVDF is 50: 40: 10.
and (3) impregnating the base membrane to be modified such as a PE diaphragm or a PP diaphragm on the two sides by a pulling method, taking out, and drying to obtain the modified diaphragm. Through testing, the thermal stability, mechanical property, electrochemical property, interface stability and other properties of the modified diaphragm are obviously improved.
In a second aspect, the present invention provides a method for preparing a modified ceramic matrix composite membrane, comprising the following steps:
s1, preparing lithium-containing conductive ceramic LLZTO powder; preparing a polyethylene oxide electrolyte film-forming material which is PEO-LiTFSI or PEO-LiFSI, and wherein the molar ratio of PEO to Li is 6-10: 1;
s2, adding glacial acetic acid accounting for 8-12% of the mass of the lithium-containing conductive ceramic powder and DMF accounting for 8-12% of the mass of the lithium-containing conductive ceramic powder into the lithium-containing conductive ceramic LLZTO powder, and fully mixing and stirring to prepare mixed slurry of the glacial acetic acid and the LLZTO;
s3, mixing a polyethylene oxide electrolyte film-forming material, mixed slurry of glacial acetic acid and LLZTO and PVDF binder, adding a powder dispersant, and fully stirring to obtain composite modified slurry; in the composite modified slurry, the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the PVDF is 45-55: 36-44: 8-12;
and S4, dipping the front and back surfaces of the base membrane to be modified in the composite modified slurry by adopting a pulling method, and drying to obtain the modified ceramic matrix composite membrane.
According to a preferred embodiment of the present invention, in S1, the lithium-containing conductive ceramic LLZTO has a chemical formula of Li 7-x La 3 Zr 2- x Ta x O 12 (ii) a Wherein, 0<x<1。
According to a preferred embodiment of the present invention, in S1, LLZTO is Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 Or Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 (ii) a More preferably Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 . When x is 0.25, the conductive ceramic LLZTO has the best effect of modifying a PE-based film or a PP-based film.
According to a preferred embodiment of the present invention, in S1, in the polyethylene oxide electrolyte film-forming material, a molar ratio of PEO to Li is 8: 1.
respectively weighing PEO and LiTFSI or LiFSI according to a preset molar ratio, and then uniformly mixing to obtain the polyethylene oxide electrolyte film-forming material.
According to the preferred embodiment of the present invention, in S2, glacial acetic acid accounting for 10% of the mass of the lithium-containing conductive ceramic LLZTO powder and DMF accounting for 10% of the mass of the lithium-containing conductive ceramic powder are added.
According to the preferred embodiment of the present invention, in S3, the mass ratio of the polyethylene oxide electrolyte film-forming material, the LLZTO powder, and the PVDF in the composite modified slurry is 50: 40: 10. when the ratio of the three materials is 50: 40: 10 hours, the composite modified slurry has the best modification effect on the PE base film or the PP base film, the electrochemical performance of the diaphragm is optimal, and the conductive ceramic LLZTO can be firmly combined on the base film, so that the modified film and the electrode have good interface stability. In addition, experiments also prove that the composite modified slurry meeting the proportion can ensure that the modified diaphragm obtains the best mechanical property and thermal stability.
According to a preferred embodiment of the present invention, in S3, the powder dispersant is adata powder dispersant AD 8085.
By adding the powder dispersing agent (such as the Adam powder dispersing agent AD8085), the electrostatic repulsion generated after the powder dispersing agent is adsorbed on the small particles disperses the particles, so that the prepared slurry is dispersed more quickly, the agglomeration phenomenon of the LLZTO is avoided, meanwhile, the stirring time of the slurry is effectively shortened, and compared with the condition that the powder dispersing agent is not added, the stirring time can be shortened by half.
According to the preferred embodiment of the present invention, in S4, the base film to be modified is a PE base film, and the number of dipping times is 3; the drying condition is that the mixture is dried for 10 to 15 hours at a temperature of between 75 and 85 ℃.
In a third aspect, the present invention provides a modified ceramic matrix composite membrane prepared by the method of any one of the above embodiments.
(III) advantageous effects
The invention has the beneficial effects that:
(1) the invention uses the inorganic conductive ceramic LLZTO to modify PE or PP diaphragmThe mechanical strength and the thermal stability of the modified diaphragm can be effectively improved; when the base film is PE, it is compared with SiO 2 The inorganic conductive ceramic LLZTO is used for improving the tensile strength of the diaphragm, so that the effect of improving the tensile strength of the diaphragm is more obvious. Wherein LLZTO (Li) 7-x La 3 Zr 2-x Ta x O 12 ) When x of (2) is 0.25, the modification effect is most prominent. Under the same condition, the conductivity of the LLZTO modified PE diaphragm is about 2 times higher than that of the LLZO with a tetragonal structure.
The PE separator which is not modified usually has a low melting point (140-150 ℃), the LLZTO has high thermal stability (the self-high temperature resistance reaches more than 600 ℃), and the thermal stability of the PE separator can be improved by adding the LLZTO into the PE separator, so that the thermal stability plays an important role in the safety of a battery.
(2) Under the condition of not adding PVDF, the adhesion of the LLZTO on the surface of the base film is poor, and the LLZTO is easy to fall off from a pole piece in the long-time working process of the battery. The invention introduces the PVDF as the binder, which can greatly increase the viscosity of the composite modified slurry, so that the LLZTO can be firmly combined on the PE/PP basal membrane, thereby improving the interface stability of the modified diaphragm and the electrode. In addition, PVDF can also effectively prevent crystallization of PEO in the polyethylene oxide electrolyte film-forming material, and improve the electrochemical performance of the modified PE diaphragm. In the prior art, PEO-LiTFSI (or together with inorganic conductive ceramic) is used as a modified material of the separator, but the ion conductivity of the separator is poor due to crystallization of PEO. In the invention, a certain amount of PVDF is added into the composite modified slurry, and the PVDF can be dispersed into a PEO (polyethylene oxide) heterogeneous system, thereby inhibiting the crystallization of PEO-LiTFSI and improving the electrochemical performance of the modified PE diaphragm. The combination of the inorganic conductive ceramic LLZTO and the PVDF adhesive can effectively improve the mechanical property and the thermal stability of the PE diaphragm.
(3) In the preparation method, glacial acetic acid accounting for about 10 percent of the mass of the lithium-containing conductive ceramic powder is added into the lithium-containing conductive ceramic LLZTO powder, and the technical effects comprise that:
firstly, the alkalinity of a mixed system of LLZTO and DMF is reduced in advance, and the follow-up is preventedThe added PVDF is decomposed in a high-alkaline environment, so that the PVDF alkali decomposition effect is effectively inhibited, the PVDF and the LLZTO have better compatibility, the formation of Lewis acid-base effect between the PVDF and the LLZTO is facilitated, and the electrochemical performance of the composite modified slurry system is improved. The LLZTO and DMF are mixed to easily form an environment with higher alkalinity, so that the alkalinity can be reduced by adding glacial acetic acid, the PVDF is prevented from being subjected to alkaline decomposition, and an ideal composite modified slurry system cannot be constructed due to the PVDF decomposition. ② in addition, LLZTO is very sensitive to moisture, and when exposed to atmospheric environment, it will react with water molecules to form LiOH, which will react with carbon dioxide to form Li 2 CO 3 。Li 2 CO 3 The presence of (A) inhibits the formation of a highly conductive layer, reduces the electropositivity of the LLZTO particles, and impairs their synergy with the lithium salt in PEO-LiTFSI. However, Li in the prior art is not taken into consideration 2 CO 3 The impurities are removed, and part of the disclosed technology needs to prepare and store the modified composite slurry in an argon atmosphere or a glove box, so that the industrial application is very unfavorable. In the present invention, glacial acetic acid, which can remove Li, and DMF, which is used to exclude moisture and air, are added to LLZTO 2 CO 3 Impurities, so that the LLZTO is purified, the synergistic effect of the LLZTO and lithium salt in PEO-LiTFSI is enhanced, and the formation of a high conductive layer is promoted. And glacial acetic acid belongs to weak acid, has no strong oxidizing property, and cannot cause adverse effect on the PE base film. Glacial acetic acid cannot be replaced by other oxidizing acids. And the carboxyl of glacial acetic acid in the composite modified slurry can also provide an additional transmission channel for the transportation of lithium ions, and the ionic conductivity and electrochemical performance of the modified slurry and the modified diaphragm are improved.
In conclusion, the composite modified slurry prepared by the invention realizes the synergistic interaction of LLZTO, PEO-LiTFSI, PVDF and glacial acetic acid on the modification function of the diaphragm, so that the modified diaphragm which has good mechanical property and thermal stability, excellent tensile strength, high ionic conductivity and good interface stability with the electrode is prepared; compared with the prior art, the preparation method of the invention is only used for preparing materials, stirring and mixing materials and dipping and lifting, has very simple operation method, does not need to be carried out in an argon or glove box in the whole preparation process, has no strict requirement on the environment in the preparation process of the composite modified slurry, does not need special production equipment, and is very convenient for industrialized application. The composite modified slurry with the special formula components enhances a series of performances of the PE diaphragm, and has the advantages of adjustable film thickness, low cost, environmental protection, good repeatability and easy batch production.
Drawings
FIG. 1 is an SEM image of cubic phase LLZTO prepared in example 1 of the present invention.
Fig. 2 is an SEM image of the modified PE separator prepared in example 1 of the present invention.
Detailed Description
For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.
Example 1
The embodiment provides a preparation method of a modified ceramic matrix composite membrane, which comprises the following steps:
(1) preparing powder of the lithium-containing conductive ceramic LLZTO;
according to 2.83g of LiOH H 2 O、2.15g ZrO 2 、9.77g La 2 O 3 、1.1g Ta 2 O 5 Put into a zirconia ball mill pot, 50ml of isopropanol is added, and ball milled with zirconia balls at 250rpm for 6 hours. The resulting slurry was dried in a forced air oven at 80 ℃ for 12 hours. The resulting powder was calcined in a muffle furnace at 950 ℃ for 12 hours using an alumina square boat. Then calcining the powder in a tube furnace at 1150 ℃ for 14 hours in an air environment, and performing ball milling for 6 hours again to obtain Li 7-x La 3 Zr 2-x Ta x O 12 White powder, designated as LLZTO, where x is 0.25. The SEM image of the prepared cubic phase LLZTO is shown in FIG. 1.
(2) According to the PEO: PEO and LiTFSI were weighed at a molar ratio of Li to 8:1 and mixed for 2h with stirring to produce a polyethylene oxide electrolyte membrane-forming material, designated PEO-LiTFSI.
(3) Mixing LLZTO powder with 10 wt% DMF and 10 wt% glacial acetic acid, stirring for 2 hr to obtain mixed slurry of glacial acetic acid and LLZTO, and recording as LLZTO-10% glacial acetic acid; glacial acetic acid is used to reduce the alkalinity of the mixed slurry.
(4) 50 parts by mass of PEO-LiTFSI, LLZTO-10% glacial acetic acid (containing 40 parts by mass of LLZTO powder) and 10 parts by mass of PVDF are mixed, and simultaneously 1 wt% of Auda powder dispersant AD8085 of the total amount of the mixed materials is added and stirred for 12 hours to obtain composite modified slurry which is marked as 50[ PEO-LiTFSI ] -40[ LLZTO ] -10PVDF + 10% glacial acetic acid.
(5) The front and back surfaces of a pure PE film (a commercial product) are dipped into the composite modified slurry for 3 times by adopting a pulling method, and the modified PE film is obtained by drying for 12h at 80 ℃.
The SEM image of the modified PE separator is shown in fig. 2, and it can be seen that a large amount of nano conductive ceramic LLZTO powder is attached to the surface of the base film. The modified PE diaphragm is subjected to breakdown voltage test, and the breakdown voltage is 1.69 KV; tensile strength of 25.3MPa and thickness of 20 μm, while having excellent thermal stability: the surface does not shrink or melt after heat preservation for 2 hours at 150 ℃. And (3) performing a tensile test on the modified PE diaphragm, standing for 10min under the pressing and dropping action of a weight of 300g, wherein the modified PE diaphragm is not fractured or obviously deformed, and the mechanical property of the diaphragm is good. The ionic conductivity was tested to be about 3.4 x 10 -4 S/cm。
Example 2
This example is different from example 1 in that LiOH. H was adjusted in step (1) 2 O、ZrO 2 、La 2 O 3 、Ta 2 O 5 To give Li 7-x La 3 Zr 2-x Ta x O 12 White powder, wherein x is 0.4. The remaining steps and conditions were the same as in example 1.
Example 3
This example differs from example 1 in that the PEO was adjusted in step (2): PEO and LiTFSI were weighed at a molar ratio of Li to 10:1 and mixed with stirring to obtain a polyethylene oxide electrolyte film-forming material, designated PEO-LiTFSI.
Example 4
This example differs from example 1 in that the PEO was adjusted in step (2): PEO and LiTFSI were weighed at a molar ratio of Li to 6:1 and mixed with stirring to obtain a polyethylene oxide electrolyte film-forming material, designated PEO-LiTFSI.
Example 5
This example is different from example 1 in that DMF and glacial acetic acid are added in an amount of 8 wt% based on the conductive ceramic LLZTO powder in step (3) to prepare a mixed slurry of glacial acetic acid and LLZTO, which is referred to as LLZTO-8% glacial acetic acid.
Example 6
This example is different from example 1 in that DMF and glacial acetic acid were added in an amount of 12 wt% based on the conductive ceramic LLZTO powder in step (3) to prepare a mixed slurry of glacial acetic acid and LLZTO, which is designated as LLZTO-12% glacial acetic acid.
Example 7
This example is different from example 1 in that the blending ratio of PEO-LiTFSI, LLZTO-10% glacial acetic acid, and PVDF was adjusted in step (4) so that the blending ratio of PEO-LiTFSI, LLZTO powder, and PVDF was 45:45:10 by mass. 1 wt% of Adam powder dispersant AD8085 was also added and stirred for 12 hours to obtain a composite modified slurry, which was designated as 45[ PEO-LiTFSI ] -45[ LLZTO ] -10PVDF + 10% glacial acetic acid.
Example 8
This example is different from example 1 in that the blending ratio of PEO-LiTFSI, LLZTO-10% glacial acetic acid, and PVDF was adjusted in step (4) so that the blending ratio of PEO-LiTFSI, LLZTO powder, and PVDF was 54:36:10 by mass. 1 wt% of Adam powder dispersant AD8085 was also added and stirred for 12 hours to obtain a composite modified slurry, which was designated 54[ PEO-LiTFSI ] -36[ LLZTO ] -10PVDF + 10% glacial acetic acid.
Example 9
This example is different from example 1 in that the blending ratio of PEO-LiTFSI, LLZTO-10% glacial acetic acid, and PVDF was adjusted in step (4) such that the blending ratio of PEO-LiTFSI, LLZTO powder, and PVDF was 48:40:12 by mass. 1 wt% of Adam powder dispersant AD8085 was also added and stirred for 12 hours to obtain a composite modified slurry, which was designated 48[ PEO-LiTFSI ] -40[ LLZTO ] -12PVDF + 10% glacial acetic acid.
Example 10
This example is different from example 1 in that the blending ratio of PEO-LiTFSI, LLZTO-10% glacial acetic acid, and PVDF was adjusted in step (4) such that the blending ratio of PEO-LiTFSI, LLZTO powder, and PVDF was 55:36:9 by mass. 1 wt% of Adam powder dispersant AD8085 was also added and stirred for 12 hours to obtain a composite modified slurry, which was designated as 55[ PEO-LiTFSI ] -36[ LLZTO ] -9PVDF + 10% glacial acetic acid.
The modified PE separators prepared in examples 2 to 10 were tested for their resistance to breakdown voltage, tensile strength, thickness, thermal stability, tensile test, ionic conductivity, etc., and the results are shown in table 1:
TABLE 1
Figure BDA0003691738470000091
Figure BDA0003691738470000101
Note: the thermal stability was maintained at 150 ℃ for 2h and the surface was observed for shrinkage/melting. The tensile test is to fix one end of the modified PE diaphragm on a bracket by a clamp, and to stand the other end by a weight of 300g for 10min, and to observe whether the modified PE diaphragm is broken or deformed.
The significant technical effects of the solution of the present invention are further illustrated below in connection with comparative examples.
Comparative example 1
This comparative example is a commercial PE separator product before modification.
Comparative example 2
The comparison example adopts PI (polyimide) as a binder and adopts nano SiO 2 And modifying the pure PE membrane. The modification method comprises the following steps: 0.25g of soluble PI was dissolved in NMP, 2.25g of nano SiO was added 2 (the grain diameter is 30-50nm), stirring for 1h, and performing ultrasonic dispersion for 30min to prepare a modified coating solution. And (3) coating the coating solution on the surfaces of the two sides of the PE diaphragm, and fully soaking, and drying NMP in vacuum at 60 ℃ to obtain the modified composite membrane.
Comparative example 3
This comparative example is based on example 1 andthe LLZTO used is replaced by LLZO without Ta doping, i.e. Li 7 La 3 Zr 2 O 12 . Other steps and conditions were the same as in example 1.
Comparative example 4
This comparative example is based on example 1, replacing the PVDF used by an equal amount of PI.
Comparative example 5
This comparative example is based on example 1, and no PVDF was added in step (4), and the composite modified slurry was 50[ PEO-LiTFSI ] -50[ LLZTO ] + 10% glacial acetic acid. Other steps and conditions were the same as in example 1.
Comparative example 6
This comparative example was made in the same manner as in example 1 except that glacial acetic acid used in step (3) was removed. Other steps and conditions were the same as in example 1.
The modified PE membranes prepared in comparative examples 1-6 were tested for various properties such as breakdown voltage resistance, tensile strength, thermal stability, tensile test, ionic conductivity, etc., and the results are shown in table 2:
TABLE 2
Group of Breakdown voltage resistance Thermal stability Tension test Tensile strength Ionic conductivity
Example 1 1.69KV Without shrinkage/melting No fracture/deformation 25.3MPa 3.4*10 -4 S/cm
Comparative example 1 1.00KV Significant shrinkage and melting Has obvious deformation 12MPa 1.3*10 -4 S/cm
Comparative example 2 1.58KV Without shrinkage/melting Has a certain deformation 14.2MPa 2.0*10 -4 S/cm
Comparative example 3 1.56KV Without shrinkage/melting No fracture/deformation 21.3MPa 1.5*10 -4 S/cm
Comparative example 4 1.60KV Without shrinkage/melting No fracture/deformation 22.6MPa 2.1*10 -4 S/cm
Comparative example 5 1.43KV Slight crimp No fracture/deformation 15.8MPa 1.4*10 -4 S/cm
Comparative example 6 1.50KV Without shrinkage/melting No fracture/deformation 22.7MPa 1.8*10 -4 S/cm
In summary, as can be seen from comparison between example 1 and comparative example 1, compared with a pure PE film before modification, the modified PE diaphragm prepared by the present invention has overall and significant improvements in puncture resistance, thermal stability, tensile property, ionic conductivity, etc., and a novel PE diaphragm with excellent comprehensive properties is obtained. Compared with the comparative example 2 and the example 1, the modification method of the invention is compared with the inorganic nano SiO 2 And the PE membrane prepared by the method is obviously improved in the aspects of ionic conductivity and tensile strength. Compared with the comparative example 3, the Ta-doped LLZTO adopted in the invention can stably form a cubic phase, and the ionic conductivity is higher than that of a LLZO modified PE diaphragm under the same condition; in addition, the LLZTO modification makes the PE separator have good interface stability. As can be seen from example 1 compared to comparative examples 4 and 5, PVDF can be better dispersed into PEO to effectively prevent PEO from crystallizing to obtain higher ionic conductivity, and can effectively increase the adhesion of conductive ceramic LLZTO, thereby stabilizing the interface of PE separator and electrode, having more adhesion of LLZTO and contributing to higher thermal stability and tensile strength. PE separator prepared in the absence of PVDF, ion of which is comparable to that of example 1The conductivity decreases significantly and the interface stability becomes poor. This is mainly due to modification of the PE film by PEO-LiTFSI and LLZTO alone, the LLZTO powder adhesion becomes poor, so the thermal stability and conductivity modification of the LLZTO is insignificant, while PEO crystallization also reduces the ionic conductivity. As can be seen from example 1 compared with comparative example 6, the ionic conductivity of the modified PE separator was decreased after removing glacial acetic acid in the preparation method, mainly due to alkali decomposition of PVDF in the strongly alkaline mixed system of LLZTO and DMF, and a small amount of Li inevitably contained in LLZTO 2 CO 3 Negative effects of impurities.
In conclusion, the composite modified slurry prepared by the invention realizes the synergistic interaction of LLZTO, PEO-LiTFSI, PVDF and glacial acetic acid on the modification function of the diaphragm, so that the modified diaphragm which has good mechanical property and thermal stability, excellent tensile strength, high ionic conductivity and good interface stability with the electrode is prepared.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. A composite modified slurry for modifying a battery separator, comprising: polyethylene oxide electrolyte film-forming material, mixed slurry of glacial acetic acid and LLZTO powder and binder PVDF;
wherein the polyethylene oxide electrolyte film-forming material is PEO-LiTFSI or PEO-LiFSI, and the molar ratio of PEO to Li is 6-10: 1;
mixing glacial acetic acid with LLZTO powder in the presence of DMF as solvent, and Li as LLZTO powder 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (ii) a Glacial acetic acid is LLZTO powder quality8-12% of (A), wherein the amount of DMF is 8-12% of the mass of the LLZTO powder;
wherein the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the binder PVDF is 45-55: 36-44: 8-12.
2. The preparation method of the modified ceramic matrix composite membrane is characterized by comprising the following steps:
s1, preparing powder of lithium-containing conductive ceramic LLZTO; preparing a polyethylene oxide electrolyte film-forming material which is PEO-LiTFSI or PEO-LiFSI, and wherein the molar ratio of PEO to Li is 6-10: 1;
s2, adding glacial acetic acid accounting for 8-12% of the mass of the lithium-containing conductive ceramic powder and DMF accounting for 8-12% of the mass of the lithium-containing conductive ceramic powder into the lithium-containing conductive ceramic LLZTO powder, and fully mixing and stirring to prepare mixed slurry of the glacial acetic acid and the LLZTO;
s3, mixing a polyethylene oxide electrolyte film-forming material, mixed slurry of glacial acetic acid and LLZTO and PVDF binder, adding a powder dispersant, and fully stirring to obtain composite modified slurry; in the composite modified slurry, the mass ratio of the polyethylene oxide electrolyte film-forming material to the LLZTO powder to the PVDF is 45-55: 36-44: 8-12;
and S4, dipping the front and back surfaces of the base membrane to be modified in the composite modified slurry by adopting a pulling method, and drying to obtain the modified ceramic matrix composite membrane.
3. The method according to claim 1, wherein the lithium-containing conductive ceramic LLZTO in S1 has a chemical formula of Li 7-x La 3 Zr 2-x Ta x O 12 (ii) a Wherein, 0<x<1。
4. The method according to claim 1, wherein in S1, the conductive lithium-containing ceramic LLZTO is Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 。
5. The production method according to claim 1, wherein in S1, in the polyethylene oxide electrolyte film-forming material, the molar ratio of PEO to Li is 8: 1.
6. the method according to claim 1, wherein glacial acetic acid in an amount of 10% and DMF in an amount of 10% by mass based on the mass of the lithium-containing conductive ceramic LLZTO powder is added to the lithium-containing conductive ceramic LLZTO powder in S2.
7. The method according to claim 1, wherein in S3, the weight ratio of the polyethylene oxide electrolyte film-forming material, the LLZTO powder and the PVDF in the composite modified slurry is 50: 40: 10.
8. the method according to claim 1, wherein in S3, the powder dispersant is Adam powder dispersant AD 8085.
9. The production method according to claim 1, wherein in S4, the base film to be modified is a PE base film, and the number of impregnation times is 3; the drying condition is that the mixture is dried for 10 to 15 hours at a temperature of between 75 and 85 ℃.
10. A modified ceramic matrix composite membrane produced by the method of any one of claims 2 to 9.
CN202210666333.2A 2022-06-13 2022-06-13 Composite modified slurry, modified ceramic-based composite membrane and preparation method Pending CN115084779A (en)

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CN114583246A (en) * 2022-02-21 2022-06-03 南昌大学 Solid-state lithium ion battery and preparation method thereof

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