CN113224374A - Composite electrolyte membrane and preparation method thereof - Google Patents

Composite electrolyte membrane and preparation method thereof Download PDF

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Publication number
CN113224374A
CN113224374A CN202010069549.1A CN202010069549A CN113224374A CN 113224374 A CN113224374 A CN 113224374A CN 202010069549 A CN202010069549 A CN 202010069549A CN 113224374 A CN113224374 A CN 113224374A
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electrolyte
garnet
grinding
organic polymer
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吴剑文
李山山
凌仕刚
沙金
朱卫泉
苏迎春
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Tianjin Guoan MGL New Materials Technology Co Ltd
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Tianjin Guoan MGL New Materials Technology 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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Abstract

The invention discloses a composite electrolyte membrane, which is prepared by compounding a garnet electrolyte and an organic polymer electrolyte, and particularly, after the garnet electrolyte is mixed with a proton exchanger, lithium ions on the surface of the garnet electrolyte can be replaced by hydrogen protons by using a grinding means to obtain a substituted garnet electrolyte, and then the substituted garnet electrolyte is compounded with the organic polymer electrolyte, so that the ionic conductivity of the obtained electrolyte membrane can be greatly improved.

Description

Composite electrolyte membrane and preparation method thereof
Technical Field
The invention belongs to the field of lithium ion battery solid electrolyte materials, and particularly relates to a composite electrolyte membrane compounded by a proton-substituted garnet electrolyte and an organic polymer and a preparation method thereof.
Background
The lithium ion battery is an important energy storage device in multiple fields such as communication electronic products, mobile computers, portable entertainment equipment, daily electric tools, new energy vehicles and energy storage, and with the high-speed development of industries such as electronic products, new energy vehicles and energy storage application, the market puts higher requirements on the energy density, the cycle performance and the safety performance of the lithium ion battery. The safety of the current power battery, particularly the safety performance of the high-energy density power battery, is still deficient.
The existing lithium ion battery uses liquid electrolyte, has flammability and poor thermal stability, and is easy to cause explosion accidents. The solid electrolyte material is used for replacing or partially replacing the liquid electrolyte material, so that the safety performance of the battery can be improved, the grouping efficiency of the power battery is improved in grouping, and the overall energy density of the battery pack is improved.
The solid electrolyte includes an inorganic solid electrolyte and a polymer solid electrolyte, wherein a garnet solid electrolyte among the inorganic solid electrolytes has received a wide attention due to its high ion conductivity. But the interface contact resistance of garnet solid-state electrolytes is too large compared to other types of solid-state electrolytes.
PEO polymer in the polymer solid electrolyte is concerned by the advantages of simple preparation process, low cost, low toxicity, high dielectric constant and the like. However, the generally higher glass transition temperature of PEO results in less movement of the polymer segments, which in turn results in slower ion migration and lower conductivity (-10)-6S/cm) and therefore further modification thereof is required to increase the conductivity.
Although the inorganic solid electrolyte is used in combination with the polymer solid electrolyte, the interfacial resistance between the electrolyte and the electrode can be well reduced. However, the addition of the polymer inevitably reduces the conductivity of the solid electrolyte, and the demand of the high-performance solid lithium battery cannot be met.
Disclosure of Invention
In order to solve the above problems, the present inventors have made intensive studies to design a composite electrolyte membrane in which lithium ions on the surface of a garnet-type electrolyte are replaced with hydrogen protons by a grinding means after mixing the garnet-type electrolyte matrix with a proton exchanger, thereby obtaining a substituted garnet electrolyte. Then, the substituted garnet electrolyte and the organic polymer electrolyte are compounded, and the ionic conductivity of the compounded electrolyte membrane can be greatly improved, thereby completing the invention.
Specifically, the present invention aims to provide the following:
the present invention provides, in a first aspect, a substituted garnet electrolyte comprising a garnet electrolyte matrix and a proton exchanger, which are ground.
In a second aspect, the present invention provides a composite electrolyte membrane obtained by combining the substituted garnet electrolyte according to the first aspect of the present invention and an organic polymer electrolyte.
A third aspect of the present invention provides a method for producing a composite electrolyte membrane, the method comprising the steps of:
step 1: grinding the garnet electrolyte matrix in a proton exchanger to obtain a substituted garnet electrolyte;
step 2, preparing an organic polymer electrolyte solution;
step 3, mixing the substituted garnet electrolyte with an organic polymer electrolyte solution to obtain a mixed slurry;
and 4, pouring the mixed slurry into a grinding tool for casting forming to obtain the composite electrolyte membrane.
The invention has the advantages that:
1) according to the substituted garnet electrolyte provided by the invention, lithium ions on the surface of the garnet electrolyte can be replaced by hydrogen protons by grinding in a proton exchanger, so that the unit cell parameters of the electrolyte are increased;
2) the composite electrolyte membrane provided by the invention is compounded by adopting a substituted garnet electrolyte and an organic polymer electrolyte, and the electric conductance of the composite electrolyte membrane isThe ratio is 1.05X 10 or more-4S/cm, more preferably 1.55X 10 or more-4S/cm, more preferably at least 2.05X 10-4S/cm, the requirement of a high-performance solid-state lithium battery can be met;
3) the preparation method for preparing the substituted garnet electrolyte and the composite electrolyte membrane, provided by the invention, has the advantages of simple process, convenience in operation and easiness in commercial popularization.
Drawings
Fig. 1 shows XRD patterns of samples in examples and comparative examples.
Detailed Description
The invention is explained in more detail below with reference to the figures and examples. The features and advantages of the present invention will become more apparent from the description.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
The present invention provides, in a first aspect, a substituted garnet electrolyte prepared by milling a garnet electrolyte matrix and a proton exchanger.
Among them, the garnet electrolyte is a typical inorganic solid electrolyte material, has the advantages of a wide electrochemical window, favorable electrochemical stability, stable contact with metallic lithium and the like, and is widely applied to the field of all-solid batteries. However, the garnet-type electrolyte still has a problem of low ionic conductivity. In the present invention, the applicant has found through extensive studies that lithium ions on the surface of a garnet-type electrolyte can be replaced with hydrogen protons by a polishing means after mixing the garnet-type electrolyte with a proton exchanger, and that the ionic conductivity of the electrolyte material can be significantly improved.
In a preferred embodiment, the garnet-type electrolyte matrix is a lithium lanthanum zirconium oxide-based electrolyte.
Further preferably, the garnet-type electrolyte matrix is a lithium lanthanum zirconium oxide-based electrolyte doped with a metal element, wherein the metal element comprises at least one of A, D and E, wherein:
a represents one or more elements selected from B, Al, Ga, In, Fe, Co and Ni,
d represents one or more elements selected from Nb, Ta and V,
e represents one or more elements selected from Cr, W and Mo.
It is further preferred that the first and second liquid crystal compositions,
a represents one or more elements selected from B, Al, Ga and In,
d represents one or more elements selected from Nb and Ta,
e represents one or more elements selected from W and Mo.
More preferably still, the first and second liquid crystal compositions are,
a represents an Al element, and A represents an Al element,
d represents an element of Nb and is represented by,
e represents a W element.
In a preferred embodiment, the ionized valences of the element a are +3, the ionized valences of the element D are +5, and the ionized valences of the element E are + 6.
In a preferred embodiment, the garnet-type electrolyte matrix has a composition formula of Li2a-3x-y- 2zAxLa3Zr2-y-zDyEzO8.5+a. The proportion of each component except oxygen in the composition formula is the material input ratio of the material amount of each element in the raw materials, and the composition formula can be verified by the mass change before and after the reaction.
Preferably, the relationship of a, x, y and z in the composition formula is:
3.4≤a≤4.2
0≤x≤0.4
0≤y≤0.6
0≤z≤0.4
further preferably, the relationship of a, x, y and z in the composition formula is:
3.5≤a≤4.0
0≤x≤0.3
0≤y≤0.5
0≤z≤0.3
more preferably, in the composition formula, a is 3.625, x is 0.2, y is 0.25, and z is 0. Namely, the compositional formula of the garnet-type electrolyte matrix is Li6.4Al0.2La3Zr1.75Nb0.25O12.125。
In a preferred embodiment, the garnet-type electrolyte matrix is prepared as follows:
step 1, mixing raw materials to obtain mixed powder;
in a preferred embodiment, the raw materials include a Li-containing compound, a La-containing compound, and a Zr-containing compound.
Wherein the Li-containing compound is selected from Li2O or decomposable to Li at a high temperature of 400 ℃, preferably 700 ℃, more preferably 900 ℃ or higher2O and compounds of volatile constituents, e.g. LiOH, LiNO3Or Li2CO3。
The La-containing compound is selected from La2O3Or decomposable to La at a high temperature of 400 ℃, preferably 700 ℃, more preferably 900 ℃ or higher2O3And compounds of volatile constituents, e.g. La (OH)3、La(NO3)3Or La2(CO3)3。
The Zr-containing compound is selected from ZrO2Or decomposable into ZrO at a high temperature of 400 deg.C, preferably 700 deg.C, more preferably 900 deg.C or higher2And compounds of volatile constituents, e.g. Zr (OH)4、Zr(NO3)4Or Zr3(CO3)O5(zirconium basic carbonate).
In a preferred embodiment, the feedstock further comprises at least one of a compound comprising a, a compound comprising D, a compound comprising E.
Wherein a is one or more elements selected from B, Al, Ga, In, Fe, Co, and Ni, more preferably one or more elements selected from B, Al, Ga, and In, and still more preferably an Al element. Preferably, the a-containing compound is selected from a-containing oxide, carbonate, oxalate or hydroxide, for example,Al2O3。
d is one or more elements selected from Nb, Ta, and V, more preferably one or more elements selected from Nb and Ta, and still more preferably Nb. Preferably, the D-containing compound is selected from D-containing oxides, carbonates, oxalates or hydroxides, for example, Nb2O5。
The E is selected from one or more elements selected from Cr, W and Mo, more preferably one or more elements selected from W and Mo, and even more preferably W. Preferably, the E-containing compound is selected from the group consisting of E-containing oxides, carbonates, oxalates or hydroxides, for example, WO3。
In a preferred embodiment, in step 1, Li is expressed according to the compositional formula of the garnet-type electrolyte matrix2a-3x-y-2zAxLa3Zr2-y-zDyEzO8.5+aThe molar ratio of various elements (except oxygen) in the raw materials is respectively weighed.
Preferably, the relationship of a, x, y and z in the composition formula is:
3.4≤a≤4.2
0≤x≤0.4
0≤y≤0.6
0≤z≤0.4
further preferably, the relationship of a, x, y and z in the composition formula is:
3.5≤a≤4.0
0≤x≤0.3
0≤y≤0.5
0≤z≤0.3
more preferably, in the composition formula, a is 3.625, x is 0.2, y is 0.25, and z is 0.
In a preferred embodiment, in step 1, the mixing is ball milling.
In the invention, the raw materials comprise various raw materials, the particle size of each raw material is not necessarily the same, and the raw materials are difficult to be uniformly mixed by simple mechanical stirring and mixing. The ball milling mixing can apply certain extrusion force to the mixed materials in the mixing process to achieve the grinding effect, so that the mixed powder is uniform in particle size, the powder can be mixed more uniformly, and the prepared electrolyte is excellent in electrical property.
In a preferred embodiment, the type of ball milling is not particularly limited, and dry ball milling or wet ball milling may be used.
Compared with dry ball milling, the slurry obtained by wet ball milling is more uniform and the grinding efficiency is high. The reason is that the materials to be milled are sometimes adhered to the milling balls during dry milling, so that the milling efficiency is reduced, and the wet milling can avoid the phenomenon due to the addition of the mixed medium, so that the milling efficiency is improved.
In a preferred embodiment, the solvent added in the wet ball milling is deionized water.
In a preferred embodiment, in the ball milling, the milling balls are selected from one or more of alumina milling balls, zirconia milling balls, stainless steel milling balls, quartz sand milling balls.
Grinding balls are grinding media, and generally, the higher the density of the grinding balls, the stronger the grinding ability, and the higher the grinding efficiency. Therefore, in the present invention, the grinding balls are preferably zirconia grinding balls.
In a preferred embodiment, the grinding balls comprise big balls and small balls, and the ratio of the number of the big balls to the number of the small balls is preferably (1-6): 1, more preferably (3-4): 1, more preferably 3: 1.
This is because the impact and grinding action of the grinding balls can be fully exerted by mixing the grinding balls of different sizes in a certain proportion and loading the mixture into a ball mill for use. Wherein the large balls mainly play a role of impact, and the small balls mainly play a role of grinding.
Preferably, the large sphere has a diameter of 3 to 30mm, more preferably 5 to 20mm, and still more preferably 10 mm. The diameter of the small spheres is preferably 50% to 80%, more preferably 60% to 70%, and still more preferably 65% of the diameter of the large spheres.
In a preferred embodiment, the mass ratio of the grinding balls to the raw materials is (1-7): 1, more preferably (3-5): 1, more preferably 4: 1.
The mass ratio of the grinding balls to the raw materials influences the quality of the ground powder. If the loading of the grinding balls is too small, insufficient grinding will occur, and the resulting mixed powder will have uneven particle diameters. If the loading of the grinding balls is too much, the grinding efficiency is reduced, which is not favorable for the industrial production of the product. The inventor of the invention has found through a great deal of experiments that the ball milling effect is best when the ball-to-material ratio is 4: 1.
In a preferred embodiment, the ball milling is carried out as follows: mixing for 30min-4h at the rotation speed of 100-500 rpm.
Wherein, the higher the rotating speed, the longer the ball milling time, the better the uniformity of the raw material mixing, and the higher the dispersibility. However, excessive increase in the rotation speed and time is not significant in improving the mixing effect, and energy consumption is wasted, thereby increasing production cost.
In a further preferred embodiment, in step 1, the ball milling is carried out as follows: mixing is carried out for 1h-3h at the rotation speed of 150-.
In a still further preferred embodiment, in step 1, the ball milling is performed as follows: mix for 3h at 200 rpm.
In a preferred embodiment, after the ball milling is finished, the slurry is dried for 6 to 15 hours at the temperature of between 80 and 120 ℃ to obtain mixed powder.
In a further preferred embodiment, after the ball milling is finished, the slurry is dried for 8-12h at 90-110 ℃ to obtain mixed powder.
In a more preferred embodiment, after the ball milling is finished, the slurry is dried at 100 ℃ for 10 hours to obtain a mixed powder.
Step 2, calcining the mixed powder to obtain a calcined product;
in a preferred embodiment, in step 2, the calcination is carried out as follows: heating the mixture from room temperature to 950-1050 ℃ at a heating rate of 2-8 ℃/min, and keeping the temperature for 8-16 h.
Among them, the calcination temperature and calcination time have an important influence on the properties of the garnet-type electrolyte matrix. If the calcination temperature is too low, the calcination time is too short, the reaction is insufficient, and the catalyst is obtainedThe electrolyte of (a) is relatively rich in impurity; if the calcination temperature is too high, a large amount of lithium is volatilized, and La is easily formed on the surface of the solid electrolyte2Zr2O7And the yield and the finished product conductivity are greatly influenced, the firing temperature is higher, and more energy is consumed.
The rate of temperature increase also affects the crystals of the calcined product, which in turn affects the electrical properties of the electrolyte produced. Too fast a temperature rise rate may lead to a subsequent reaction without complete decomposition of the lithium source, and the PH of the product after the reaction is too high to facilitate storage of the electrolyte material.
In a further preferred embodiment, in step 2, the calcination is carried out as follows: raising the temperature from room temperature to 980-1020 ℃ at the temperature raising rate of 3-6 ℃/min, and preserving the heat for 10-14 h.
In a more preferred embodiment, in step 2, the calcination is carried out as follows: raising the temperature from room temperature to 1000 ℃ at the heating rate of 4 ℃/min, and keeping the temperature for 12 h.
In a preferred embodiment, the temperature reduction after calcination is not particularly limited, but is preferably carried out naturally to obtain a calcined product. The production process can be simplified by adopting natural cooling, and the method is convenient for commercial popularization.
And 3, grinding the calcined product to obtain a sample.
In the invention, the calcined product obtained after calcination is sintered into blocks, the particle size is larger and has a wide range and irregular particle appearance, so that the electrochemical performance of the solid electrolyte is difficult to control. Therefore, after calcination, the obtained calcined product needs to be ground again to obtain a cubic phase garnet type electrolyte matrix with high conductivity.
In the present invention, the grinding in step 3 is not particularly limited, and the grinding may be performed manually using a millstone or mortar, or may be performed automatically using a grinder, such as a planetary ball mill, an attritor, a ball mill, or an air mill. Either wet or dry milling may be performed.
In order to reduce the cost of material synthesis preparation, air pulverization dry grinding is preferred in the invention, and the air pulverization uses low dew point dry air as a gas source to avoid surface deterioration of the material in the pulverization process.
After the grinding is finished, the garnet electrolyte matrix (lithium lanthanum zirconium oxygen-based electrolyte doped with metal elements) can be obtained.
In a preferred embodiment, the proton exchanger is an organic solvent, more preferably an organic solvent not containing alcoholic hydroxyl group, phenolic hydroxyl group and carboxyl group, and still more preferably an organic solvent containing only carbon element and hydrogen element, such as paraffin, naphthene, olefin or aromatic hydrocarbon. Specifically, organic solvents that can be selected for use in the present invention are n-hexane, cyclohexane, benzene, toluene, and the like.
In the experiments conducted by the inventors of the present invention, it was found that the unit cell parameters of the obtained powder become large after wet grinding the garnet-type electrolyte matrix in an organic solvent containing only carbon and hydrogen. ICP elemental analysis of the ground organic solvent can find that some trace lithium element is added in the ground organic solvent, but lanthanum element and zirconium element are not detected. Since the organic solvent contains only a hydrogen element and a carbon element, it is presumed that the hydrogen protons in the organic solvent undergo substitution reaction with the lithium ions on the surface of the garnet-type electrolyte matrix.
After the substitution reaction, the composition formula of the garnet-type electrolyte matrix is Li2a-3x-y-2zAxLa3Zr2-y-zDyEzO8.5+aComposition formula H converted into substituted garnet electrolytewLi2a-3x-y-2z-wAxLa3Zr2-y-zDyEzO8.5+a。
In a preferred embodiment, the unit cell parameter of the substituted garnet electrolyte is not less than 12.980, further preferably not less than 12.9900, more preferably not less than 12.9950.
In a preferred embodiment, the particle size of the substituted garnet electrolyte is in the nanometer scale, wherein the median particle size of the substituted garnet electrolyte is equal to or less than 2000nm, and equal to or more than 100nm, further preferably equal to or less than 1500nm, and equal to or more than 150nm, more preferably equal to or less than 1000nm, and equal to or more than 150 nm.
A second aspect of the present invention provides a composite electrolyte membrane, which is made by compounding a garnet electrolyte and an organic polymer electrolyte.
In a preferred embodiment, the garnet electrolyte is preferably the substituted garnet electrolyte of the first aspect of the present invention, and the organic polymer electrolyte is preferably a PEO-series polymer, and more preferably PEO-LiTFSI or PEO-LiClO4More preferably PEO-LiTFSI.
Among them, PEO is polyoxyethylene, which is a common matrix for polymer electrolytes, but because of its high crystallinity, the conductivity at room temperature is very low, generally 10-7-10-8S/cm, and therefore, the application is limited. The LiTFSI is bis (trifluoromethane sulfonyl) imide lithium, is a novel electrolyte lithium salt, has the decomposition temperature higher than 200 ℃, good thermal stability, easy ionization of lithium ions and high conductivity. By combining the two, a polymer electrolyte with high conductivity can be obtained.
In a preferred embodiment, the mass ratio of the garnet electrolyte to the organic polymer electrolyte is 1:2 to 8, more preferably 1:3 to 6, for example 1: 5.
In a preferred embodiment, the composite electrolyte membrane has an electrical conductivity of 1.05 × 10 or more-4S/cm, more preferably 1.55X 10 or more-4S/cm, more preferably at least 2.05X 10-4S/cm。
A third aspect of the present invention provides a method for producing a composite electrolyte membrane, the method comprising the steps of:
step 1: grinding the garnet electrolyte in a proton exchanger to obtain a substituted garnet electrolyte;
in a preferred embodiment, step 1 comprises the following sub-steps:
step 1-1, adding a proton exchanger into a garnet type electrolyte matrix to obtain slurry;
in a preferred embodiment, the garnet-type electrolyte matrix has a composition formula of Li2a-3x-y- 2zAxLa3Zr2-y-zDyEzO8.5+aThe preparation method is as described in the first aspect of the invention. Wherein A represents one or more elements selected from B, Al, Ga, In, Fe, Co and Ni,
d represents one or more elements selected from Nb, Ta and V,
e represents one or more elements selected from Cr, W and Mo.
It is further preferred that the first and second liquid crystal compositions,
a represents one or more elements selected from B, Al, Ga and In,
d represents one or more elements selected from Nb and Ta,
e represents one or more elements selected from W and Mo.
More preferably still, the first and second liquid crystal compositions are,
a represents an Al element, and A represents an Al element,
d represents an element of Nb and is represented by,
e represents a W element.
In a preferred embodiment, the relationship of a, x, y and z in the composition formula is:
3.4≤a≤4.2
0≤x≤0.4
0≤y≤0.6
0≤z≤0.4
further preferably, the relationship of a, x, y and z in the composition formula is:
3.5≤a≤4.0
0≤x≤0.3
0≤y≤0.5
0≤z≤0.3。
more preferably, in the composition formula, a is 3.625, x is 0.2, y is 0.25, and z is 0. That is, the compositional formula of the composition formula of the substituted garnet electrolyte is Li6.4Al0.2La3Zr1.75Nb0.25O12.125。
In a preferred embodiment, the proton exchanger is an organic solvent, more preferably an organic solvent not containing alcoholic hydroxyl group, phenolic hydroxyl group and carboxyl group, and still more preferably an organic solvent containing only carbon element and hydrogen element, such as paraffin, naphthene, olefin or aromatic hydrocarbon. Specifically, organic solvents that can be selected for use in the present invention are n-hexane, cyclohexane, benzene, toluene, and the like.
In a preferred embodiment, the ratio of the amount of the proton exchanger to the garnet-type electrolyte matrix is (50-400) ml:100g, more preferably (100-300) ml:100g, and still more preferably 200ml:100 g.
The dosage of the proton exchanger cannot be too small, otherwise, the dosage is easy to be too small due to volatilization in the ball milling process, and the substitution of hydrogen protons and lithium ions is insufficient. On the other hand, the amount of proton exchanger used may not be too large, which may make the slurry thin, adversely affect the contact between the particles and the grinding balls, and may result in a decrease in grinding efficiency. When the ratio of the amount of the proton exchanger to the garnet-type electrolyte matrix is controlled within the above range, the substitution effect is the best.
Step 1-2, adding grinding balls into the slurry for grinding;
in a preferred embodiment, the grinding balls are selected from one or more of alumina grinding balls, zirconia grinding balls, stainless steel grinding balls, quartz sand grinding balls.
The density of the grinding balls made of different materials is different, and the larger the density is, the more energy is consumed, and the more heat energy is generated through friction and collision. The generated thermal energy can raise the temperature of the slurry, thereby promoting the replacement reaction of hydrogen protons in the organic solvent and lithium ions on the surface of the garnet-type electrolyte matrix. Therefore, in the present invention, the grinding balls are preferably zirconia grinding balls.
In a preferred embodiment, the grinding balls have a diameter of 2-12mm, more preferably 2-6mm, and even more preferably 3 mm.
The smaller the diameter of the grinding ball is, the larger the contact surface with the particles to be ground is, the larger the friction acting force acting on the particle surface is, the smaller the particle size of the obtained product is, and meanwhile, the grinding time can be greatly shortened, and the volatilization of the organic solvent can be reduced as much as possible. Of course, the diameter of the grinding medium cannot be too small, otherwise, the kinetic energy of the grinding balls is small, and discharging devices such as a screen mesh are easy to block, so that the separation operation difficulty is increased.
In a preferred embodiment, the mass ratio of the grinding balls to the raw materials is (1-7): 1, more preferably (2-5): 1, more preferably 3: 1.
Wherein the raw material in step 1-2 refers to a garnet-type electrolyte matrix. The mass ratio of the grinding balls to the raw materials affects the quality of the ground powder. If the loading of the grinding balls is too small, insufficient grinding will occur, and the resulting mixed powder will have uneven particle diameters. If the loading of the grinding balls is too much, the grinding efficiency is reduced, which is not favorable for the industrial production of the product. The inventor of the invention has found through a great deal of experiments that the ball milling effect is best when the ball-to-material ratio is 3: 1.
In a preferred embodiment, the ball milling is carried out as follows: mixing for 30min-4h at the rotation speed of 100-500 rpm.
Wherein the higher the rotation speed, the more frictional heat generation, the more favorable the proton substitution reaction. However, excessive increase of the rotation speed accelerates the volatilization of the organic solvent, which causes unnecessary waste and increases the production cost.
Further preferably, the ball milling is carried out as follows: mixing is carried out for 1h-3h at the rotation speed of 150-.
More preferably, the ball milling is carried out as follows: mix for 3h at 200 rpm.
Step 1-3, drying after grinding;
in a preferred embodiment, after the end of the grinding, the slurry is subjected to centrifugal solid-liquid separation. The obtained powder can be dried after the proton exchanger is removed, and the slurry can also be directly subjected to vacuum operation.
Among them, the main purpose of baking under vacuum is to prevent the surface of the substituted garnet electrolyte from being oxidized by oxygen in the air to form high-impedance LiOH.
In a preferred embodiment, after the ball milling is finished, the liquid is centrifuged, and the slurry is dried at 80-120 ℃ for 6-15h, further preferably at 90-110 ℃ for 8-12h, and further preferably at 80 ℃ for 10h to obtain the substituted garnet electrolyte.
In a preferred embodiment, the composition formula of the substituted garnet electrolyte is H0.005Li6.395Al0.2La3Zr1.75Nb0.25O12.25。
Step 2, preparing an organic polymer electrolyte solution;
in a preferred embodiment, the organic polymer is a PEO-series polymer, and more preferably PEO-LiTFSI or PEO-LiClO4More preferably PEO-LiTFSI.
In a preferred embodiment, the solvent used for preparing the electrolyte solution is acetonitrile or distilled water, and more preferably distilled water.
The organic polymer has a higher solubility in acetonitrile than in distilled water, and acetonitrile is preferable for increasing the production rate.
In a preferred embodiment, PEO is dissolved in a solvent and stirred at 40-80 deg.C for 10-50min, more preferably at 50-70 deg.C for 20-40min, e.g. at 60 deg.C for 30min, to give a PEO solution with a mass concentration of 1-5%, more preferably 2-3%, e.g. 2.4%.
In a preferred embodiment, after stirring is complete, LiTFSI or LiClO is added to the PEO solution4Further preferably, LiTFSI is added, the temperature is kept constant, and the stirring is continued for 10 to 50min, preferably for 20 to 40min, for example, for 30min, to obtain an organic polymer electrolyte solution.
The mass ratio of PEO to LiTFSI is 1 to 10:1, more preferably 1 to 6:1, for example 4: 1.
Step 3, mixing the substituted garnet electrolyte with an organic polymer electrolyte solution to obtain a mixed slurry;
in a preferred embodiment, the substituted garnet electrolyte is added to the organic polymer electrolyte solution and stirred, and mixed uniformly to obtain a mixed slurry.
In a preferred embodiment, the mass ratio of the substituted garnet electrolyte to the organic polymer electrolyte is controlled to be 1:2 to 8, more preferably 1:3 to 6, for example 1: 5.
Wherein, when the organic polymer is PEO-LiTFSI, the mass of the organic polymer electrolyte is the sum of the masses of PEO and LiTFSI.
Step 4, pouring the mixed slurry into a grinding tool for casting forming to obtain a composite electrolyte membrane;
in a preferred embodiment, the mixed slurry is poured into a polytetrafluoroethylene mold after being uniformly stirred to form a film, the film is naturally dried, removed by tweezers and punched into round pieces.
The preparation process of the tape-casting film is not particularly limited, and any preparation process capable of obtaining the composite electrolyte film can be applied to the invention.
Examples
Example 1
0.64mol (26.88g) of LiOH. H2O，0.15mol(48.87g)La2O3，0.175mol(21.56g)ZrO2，0.0125mol(3.323g)Nb2O5And 0.01mol (1.02g) of Al2O3Ball-milling and mixing the mixed materials, wherein the solvent is deionized water, the mixing time is 3h, drying the mixed materials at 100 ℃ for 10h to obtain mixed powder, placing 100.00g of the mixed powder in a corundum crucible, heating the mixed powder at the speed of 4 ℃ per minute to 985 ℃, preserving the heat for 8h, naturally cooling the mixed powder, and grinding the cooled mixed powder to obtain the lithium lanthanum zirconium oxygen-based electrolyte Li doped with metal elements6.4Al0.2La3Zr1.75Nb0.25O12.125。
Example 2
Taking Li prepared in example 16.4Al0.2La3Zr1.75Nb0.25O12.125100g of the mixture is placed in a 500ml zirconia ball milling tank, 200ml of cyclohexane and 300g of zirconia milling balls with the diameter of 3mm are added, the mixture is ball milled for 3 hours at the rotating speed of 200rpm, and vacuum drying is carried out at 80 ℃ after the grindingSample 1 was obtained for 10 h.
0.4g of PEO was taken in an argon-protected glove box, 16g of acetonitrile was added, and the mixture was heated and stirred at 60 ℃ for 30min until the PEO was completely dissolved. Then 0.1g of litfsi was added and stirring was continued for 30 min. Finally, 0.1g of sample 1 prepared in example 1 was added, stirred for 30min and poured into a 140mm x 140mm teflon mold to be cast into a film, thereby obtaining film sample 1.
Comparative example
Comparative example 1
Taking Li6.4Al0.2La3Zr1.75Nb0.25O12.125100g, placed in a 500ml zirconia ball mill jar, and added with 300g of zirconia milling balls with a diameter of 3mm, and ball milled at 200rpm for 3 hours to obtain comparative sample 1.
0.4g of PEO was taken in an argon-protected glove box, 16g of acetonitrile was added, and the mixture was heated and stirred at 60 ℃ for 30min until the PEO was completely dissolved. Then 0.1g of litfsi was added and stirring was continued for 30 min. Finally, 0.1g of comparative sample 1 prepared in comparative example 1 was added, stirred for 30min and poured into a 140mm x 140mm teflon mold to be cast into a film, thereby obtaining film comparative sample 1.
Test example
Test example 1
XRD characterization was performed on sample 1 of example 1 and comparative sample 1 of comparative example 1, and the results are shown in fig. 1, and it can be seen from fig. 1 that the peak position of sample 1 is shifted to the left with respect to comparative sample 1, indicating that the unit cell parameter of sample 1 is larger than that of comparative sample 1.
The unit cell parameters of sample 1 and comparative sample 1 calculated by XRD are shown in table 1:
table 1 calculation of cell parameters for samples
Sample (I) Cell parameter a (× 0.1nm) Grain size (nm)
Sample 1 13.043 98
Comparative sample 1 12.952 25
The unit cell parameters of the garnet-type electrolyte matrix and the proton exchanger are obviously increased after being ground according to the unit cell parameter comparison.
Test example 2 particle size analysis of prepared sample
Table 2 particle size analysis test results
Sample (I) Median particle diameter (nm)
Sample 1 750
Comparative sample 1 3682
From the analysis results, the particle size obtained by grinding after adding the proton exchanger is smaller and tends to be more nano-scale.
Test example 3 conductivity test of composite electrolyte membrane
The conductivity was measured for film sample 1 and film comparative sample 1, the results of which are shown in table 3:
TABLE 3 conductivity test results
Sample (I) Composite film conductivity (× 10)-4S/cm)
Film sample 1 2.05
Film comparative sample 1 0.48
It can be known from comparison that the conductivity of the composite electrolyte membrane prepared by compounding the substituted garnet electrolyte and the PEO-LiTFSI is more than 4 times higher than that of the composite electrolyte membrane prepared by compounding the unsubstituted garnet electrolyte and the PEO-LiTFSI.
The present invention has been described above in connection with preferred embodiments, but these embodiments are merely exemplary and merely illustrative. On the basis of the above, the invention can be subjected to various substitutions and modifications, and the substitutions and the modifications are all within the protection scope of the invention.

Claims (9)

1. A substituted garnet electrolyte is prepared from garnet electrolyte matrix and proton exchanger through grinding.
2. The garnet electrolyte of claim 1, wherein: the garnet-type electrolyte matrix is a lithium lanthanum zirconium oxygen-based electrolyte, preferably a lithium lanthanum zirconium oxygen-based electrolyte doped with a metal element.
3. The garnet electrolyte of claim 2, wherein: the metal element includes at least one of A, D and E, wherein:
a represents one or more elements selected from B, Al, Ga, In, Fe, Co and Ni,
d represents one or more elements selected from Nb, Ta and V,
e represents one or more elements selected from Cr, W and Mo.
4. The garnet electrolyte of claim 1, wherein: the proton exchanger is an organic solvent, preferably an organic solvent which does not contain alcoholic hydroxyl groups, phenolic hydroxyl groups and carboxyl groups.
5. A composite electrolyte membrane, characterized in that: the composite electrolyte membrane is prepared by compounding a garnet electrolyte and an organic polymer electrolyte.
6. A composite electrolyte membrane according to claim 5, characterized in that: the garnet electrolyte is a substituted garnet electrolyte;
the organic polymer electrolyte is preferably PEO series polymer, and more preferably PEO-LiTFSI or PEO-LiClO4More preferably PEO-LiTFSI.
7. The composite electrolyte membrane according to claim 5 or 6, characterized in that: the mass ratio of the garnet electrolyte to the organic polymer electrolyte is 1:2 to 8, more preferably 1:3 to 6, for example 1: 5.
8. A method of producing a composite electrolyte membrane, characterized in that: the method comprises the following steps:
step 1: grinding the garnet electrolyte matrix in a proton exchanger to obtain a substituted garnet electrolyte;
step 2, preparing an organic polymer electrolyte solution;
step 3, mixing the substituted garnet electrolyte with an organic polymer electrolyte solution to obtain a mixed slurry;
and 4, pouring the mixed slurry into a grinding tool for casting forming to obtain the composite electrolyte membrane.
9. The method of claim 8, wherein: step 1 comprises the following substeps:
step 1-1, adding a proton exchanger into a garnet type electrolyte matrix to obtain slurry;
step 1-2, adding grinding balls into the slurry for grinding;
and 1-3, drying after grinding is finished.
CN202010069549.1A 2020-01-21 2020-01-21 Composite electrolyte membrane and preparation method thereof Pending CN113224374A (en)

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