KR20220074080A - Layered nanostructure-based solid electrolyte with high mechanical properties and thermal stability, and its manufacturing method - Google Patents

Abstract

The present invention relates to a method for manufacturing an ion conductive solid electrolyte film using layered granulation of clay. In the present invention, the solid electrolyte film is a solid composite film in which clay and DMSO, which are inorganic layer materials, form a brick structure in nano units, and has an ionic conductivity of 1 x 10 ^-4 S cm ^-1 or more at room temperature. , The invention relates to an ion conductive film in a flexible solid state and a method for manufacturing the same, capable of suppressing dendrites with toughness of 200 kJ m ^-2 or more by imitation of the layered structure of the cross-section of the abalone shell.

Description

Layered nanostructure-based solid electrolyte with high mechanical properties and thermal stability, and its manufacturing method

The present invention relates to an ion conductive solid electrolyte film using a layered assembly of clay and a method for manufacturing the same, and more particularly, to a layered nanostructure-based solid electrolyte having high mechanical properties and thermal stability by mimicking the layered structure of the cross section of an abalone shell, and a solid electrolyte thereof It is about the manufacturing method.

The conventional battery industry has mainly relied on liquid electrolyte systems due to the excellent wettability of liquids and excellent ionic conductivity. However, the chemical and thermal instability of liquid electrolytes can cause significant safety problems. The solid electrolyte has properties that can overcome the limitations of the liquid electrolyte. In general, solid electrolytes are classified into five types according to material components such as inorganic electrolytes, polymer electrolytes, hybrid electrolytes, gel-polymer electrolytes, and hybrid semi-solid electrolytes. Hybrid electrolytes are composed of organic and inorganic materials, and gel-polymer electrolytes and hybrid semi-solid electrolytes are mixtures of organic and inorganic materials and liquid electrolytes, respectively.

Next-generation sodium-ion batteries have similar operating mechanisms and cycling stability to conventional lithium-ion batteries. It also has several additional important advantages, such as natural abundance of sodium resources, wide lipid distribution, and low cost. Many studies have attempted to develop suitable materials for sodium-ion batteries, with recent emphasis on improving reliability and practicality. Currently, the most widely known inorganic solid sodium electrolyte is a sodium ion conductor (NASICON) having a Na _1+3x Zr ₂ (P _1-x Si _x O ₄ ) ₃ structure, and its ionic conductivity is 10 ^-3 S at a temperature of 65 ° C or higher. cm ^-1 . However, NASICON is a tough, brittle inorganic material and is inherently limited for use in mechanically flexible batteries.

Among the 2D nanoplatelets, Montmorillonite (MMT) clay dust is a nanolayered crystalline material with a thickness of about 1 nm. Montmorillonite is suitable for manufacturing multifunctional nanocomposites with useful features such as high surface area, gas barrier properties, flame retardant properties and thermal stability, and is a globally abundant and inexpensive material. Natural sodium ion having the chemical structure of ((Na,Ca) _0.33 -(Al _2-y ,Mg _y )Si ₄ O ₁₀ (OH) ₂ nH ₂ O) - Montmorillonite (Na ⁺ -MMT) nano clay is hydrophilic and is miscible with polar polymers such as polyethylene oxide (poly(ethylene oxide), PEO) and polyvinyl alcohol (PVA). In addition, although it was organically modified for mixing with most hydrophobic polymers, the material properties of the isotropic clay composite prepared by the conventional method have a limit in that it is difficult to increase the specific gravity of montmorillonite.

Conversely, nanocomposites mimicking nacres with a clay content of up to 95 wt% show improved thermal and mechanical properties. Well exfoliated clay is a necessary component to fabricate masonry structures, but small amounts of organic binders also have a significant impact in determining the performance of the resulting composite. In the case of a micro-sized plate such as alumina or boron nitride, a polymer having a high molecular structure is preferably included in the nacre structure. However, in the case of nano-sized montmorillonite, long polymer chains inhibit uniformity at the nano level. In addition, dispersion between the polymer matrix and montmorillonite tends to induce phase separation, reducing transparency. In addition, the inherently large interfacial impedance between the inorganic solid electrolyte and the solid electrode deteriorates the electrochemical properties. In addition, prevention of the occurrence of dendrites is still one of the most difficult problems.

On the other hand, organic solid electrolytes have advantages such as flexibility, light weight, good adhesion and wettability to electrodes, which also have disadvantages such as low mechanical integrity, low ionic conductivity and low oxidation resistance.

On the other hand, hybrid, gel-polymer and hybrid semi-solid electrolytes can utilize the advantages of both organic and inorganic components. In the case of a hybrid electrolyte, the Young's modulus is increased by adding an inorganic material to the polymer, but it cannot exceed the Young's modulus of the pure inorganic component. In the case of the gel polymer electrolyte, the polymer network provides mechanical stability to the mobile liquid electrolyte, but still has the problem of low mechanical strength, and in the hybrid semi-solid electrolyte, the addition of the liquid electrolyte improves the wetting or interfacial contact of the inorganic component to the electrode. By doing so, the ionic conductivity is improved. However, as the ion migration pathway becomes more complex than that of a pure liquid electrolyte, it exhibits a slower ion migration.

Important parameters for developing high-performance solid electrolytes include good mechanical integrity and thermal stability, high ionic conductivity and ion selectivity, low cost, tight integration with electrodes, and environmental friendliness. For solid electrolyte membranes, the mechanical properties must be strong enough to avoid the risk of dendrite growth. For example, dendrite growth can be suppressed with an electrolyte harder than the metal electrode itself, and in the case of a lithium-ion battery, it is known that materials with a Young's modulus of 6 GPa or higher can suppress dendrites caused by lithium. In addition to the dendrite problem, high interfacial impedance between the electrode and the electrolyte or high operating temperature due to limited ion room temperature mobility can be a limitation.

In relation to this, in Korea Patent Application Laid-Open No. 2017-0037533 (published on April 4, 2017), a first domain including a plurality of two-dimensional nanostructures (2D nanostrucutre); and a second domain including a first electrolyte and including interstitial spaces between the plurality of two-dimensional nanostructures; a composite electrolyte membrane comprising a composite electrolyte layer comprising the same, an electrochemical cell and a composite electrolyte including the same A method for manufacturing a membrane is presented.

However, there is still a need for further improvement in ionic conductivity and mechanical strength.

Korean Patent Publication No. 2017-0037533 (published on April 4, 2017)

In the present invention, in order to solve the above problems, it is intended to provide a solid electrolyte having an intimate interface contact between the electrolyte and the electrode and operability at room temperature.

In addition, in the present invention, by adding a solvent that provides the possibility of ion conduction to the nacre structure prepared using clay, a method for producing a solid electrolyte having excellent mechanical properties, flexibility, and high ionic conductivity while simultaneously having biodegradability. would like to present

In order to solve the above problems, it is an ion conductive solid electrolyte film that mimics the layered structure of the cross section of an abalone shell, and inorganic layered materials clay and DMSO form a brick and mortar structure at the nano level to have ion conductivity at room temperature. It provides an ion conductive solid electrolyte film that mimics the layered structure of the abalone shell cross-section, characterized in that.

In one embodiment, the clay may be at least one of montmorillonite, hectorite, and saponite as an inorganic layered material.

In addition, in order to solve the other problem, in the manufacturing method of the ion conductive solid electrolyte film, (a) a dispersing step of dispersing the clay in nano units; (b) a separation step of separating the nanoclay from the clay solution; (c) mixing nanoclay and DMSO to produce a nanoclay/DMSO mixture; (d) a film manufacturing step of preparing a nanoclay/DMSO mixture in the form of a film; provides a method for manufacturing an ion conductive solid electrolyte film mimicking the layered structure of the abalone shell cross-section, characterized in that it includes.

In one embodiment, the dispersing step of (a) may be to disperse the clay in nano units by applying a physical force.

In one embodiment, the dispersion step of (a) may include clay using at least one of ultrasonic dispersion, high-pressure dispersion, blending, and stirring.

In one embodiment, in the separation step of (b), the clay particles not dispersed in nano units may be removed by one or more methods of precipitation, centrifugation, adsorption separation, and extraction separation.

In one embodiment, the film manufacturing step of (d) may use one or more processes of filtration, vacuum filtration, hot press, vacuum drying, hot air drying, natural drying, extrusion, injection, and printing.

In one embodiment, a drying step of drying the prepared film within the range of -180 to 200 °C after the film manufacturing step of (d) may be further included.

In one embodiment, the DMSO in step (c) may be pure DMSO (dimethyl sulfoxide), or a solute, solvent, or solution containing 1 wt% or more of DMSO.

The solid electrolyte according to the present invention has excellent mechanical strength and flexible properties because the clay layer for suppressing dendrites is assembled in a structure that mimics nacres.

In addition, the solvent molecules providing ion conductivity distributed between the clay layers improve the ionic conductivity of the solid electrolyte according to the present invention to a level of 10 ⁻⁴ S/cm or higher at room temperature.

In addition, the solid electrolyte prepared in the nanostructured layered structure of the solvent and the clay layer according to the present invention has high thermal stability and flame retardant properties, and at the same time exhibits translucent optical properties.

In addition, the multifunctional clay/DMSO composite solid electrolyte according to the present invention is eco-friendly because it is biodegradable.

1 shows the structures of a clay plate and an organic solvent in nano units, and schematically shows the internal structure of a solid electrolyte according to an embodiment of the present invention.
2 schematically illustrates the states of molecules and particles according to each step of the manufacturing process of the present invention.
3 schematically shows the internal structure of a solid electrolyte according to an embodiment of the present invention, and schematically shows a reaction in which dendrite growth is suppressed.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is those well known and commonly used in the art.

Throughout this specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

In addition, the terms "about", "substantially", etc. used throughout this specification are used as meanings at or close to the numerical values when manufacturing and material tolerances inherent in the stated meaning are presented to help the understanding of the present application. It is used to prevent an unconscionable infringer from using the mentioned disclosure in an unreasonable way.

Throughout this specification, the description of “A and/or B” means “A or B or both”.

The specific terminology used in the detailed description that follows is for the sake of convenience and not limitation. The words 'right', 'left', 'top' and 'bottom' indicate directions in the drawings to which reference is made. The words 'inwardly' and 'outwardly' refer respectively to directions towards or away from the geometric center of the designated device, system, and members thereof. 'Anterior', 'rear', 'above', 'below' and related words and phrases indicate positions and orientations in the drawing to which the reference is made and should not be limiting. These terms include the words listed above, derivatives thereof, and words of similar meaning.

Important parameters for developing high-performance solid electrolytes include good mechanical integrity and thermal stability, high ionic conductivity and ion selectivity, low cost, tight integration with electrodes, and environmental friendliness, as described above. The properties must be robust enough to avoid the risk of dendrite growth.

To this end, the present invention provides an ion conductive solid electrolyte film simulating the nacre structure of the abalone shell, which is well known as a solid material in nature.

The nacre structure, which is the layered structure of the cross section of the abalone shell, has a toughness three times greater than that of the layered calcium carbonate aragonite, which forms a 'brick-and-mortar structure' using organic molecules as a binder. Although the mass fraction of organic molecules in the nacre structure of the abalone shell is only 5 wt%, it plays an important role in improving the mechanical strength by providing a large frictional force when the plate slides and inducing the dispersion of the strain fracture energy.

In the ion conductive solid electrolyte film according to the present invention, clay and DMSO, which are inorganic layered materials, form a brick and mortar structure at the nano level, and has a structure such as a layered structure of an abalone shell cross-section. It has ionic conductivity.

The inorganic layered material may be at least one selected from montmorillonite, hectorite, and saponite.

The ion conductivity and mechanical strength of the ion conductive solid electrolyte film according to the present invention may vary depending on the ratio of clay and DMSO, but the ionic conductivity is a distinct solid from room temperature to 2.06 x 10 ^-4 S cm ^-1 in the through-plane direction. It exhibits ionic conductivity. In addition, the mechanical tensile strength reaches ~ 55.3 ± 4.8 MPa and the mechanical toughness reaches ~ 210.2 ± 32.6 kJ m ^-2 .

In addition, the thermal stability of the solid electrolyte film of the present invention is stable even in the range of -100 to 120 °C according to differential thermal analysis, and has optical translucency.

Moreover, the clay/DMSO composite has flexible features as well as mechanical robustness due to its molecularly ordered structure, and also has flame retardant properties even in DMSO because diffusion of oxygen and combustible volatiles is also limited due to the high content of layered clay nanostructure. provides

In addition, this multifunctional clay/DMSO composite is characterized as an eco-friendly material because it can easily achieve biodegradability by feeding it to mealworms or super mealworms.

1 shows the structures of a clay plate and an organic solvent in nano units, and schematically shows the internal structure of a solid electrolyte according to an embodiment of the present invention. As shown in FIG. 1, the structure of the present invention is composed of clay and a solvent (DMSO), and depending on the composition, the clay and DMSO are structured in a layer to form crystals or may include DMSO molecules that can move freely.

In addition, the present invention provides a method of manufacturing an ion conductive solid electrolyte film having ion conductivity at room temperature.

As a specific method for mimicking the natural nacre structure, methods such as layer-by-layer (LbL) deposition, freeze drying, hot press assisted slip casting, freeze-thaw, dry casting and thermocompression bonding may be used. One or more selected from various inorganic layered nanoplatelets such as clay, boron nitride, layered double hydroxide, graphene, and Al ₂ O ₃ may be used as the nano building blocks of this nacre structure composite, and these inorganic layered nanoplatelets are It may be combined using one or more polymer binders selected from chitosan, polyvinyl alcohol, poly(methylmethacrylate, PMMA) and poly(diallyldimethyl ammonium chloride), etc. .

In the present invention, by adding a solvent that provides the possibility of ion conduction to a nacre structure prepared using clay, a method for preparing a solid electrolyte having excellent mechanical properties, flexibility, and high ionic conductivity while simultaneously having biodegradability. .

That is, in the present invention, a method for manufacturing a solid electrolyte film as a semi-solid state ion conductor composed of nanoclay and dimethyl sulfoxide (DMSO) is presented.

The solid electrolyte film according to the present invention forms a new clay-DMSO nanocomposite film in which DMSO molecules are structured at the molecular level.

More specifically, the present invention is a dispersion step of (a) dispersing the clay in nano units; (b) a separation step of separating the nanoclay from the clay solution; (c) mixing nanoclay and DMSO to produce a nanoclay/DMSO mixture; (d) a film manufacturing step of preparing a nanoclay/DMSO mixture in the form of a film; provides a method for manufacturing an ion conductive solid electrolyte film mimicking the layered structure of the abalone shell cross-section, characterized in that it includes.

The clay refers to at least one material selected from among montmorillonite, hectorite, and saponite as an inorganic layered material.

The dispersing step of (a) is characterized in that the clay is dispersed in nano units by applying a physical force. The application of the physical force does not mean chemically dispersing the nanoclay, but a physical force, for example, ultrasonic dispersion, high pressure dispersion, blending, stirring, etc. The nanoclay is dispersed by a physical force applied to the clay means that At this time, the dispersion may be dispersed without a dispersion medium, but is generally dispersed under a dispersion medium.

The nanoclay particles have a thickness of several nm to several tens of nm, preferably 10 nm or less, and have a plate-like structure having a diameter of several μm to several tens of μm.

In the separation step of (b), the clay particles not dispersed in nano units are separated from the nano clay to obtain only nano clay, and the clay particles that are not dispersed in nano units are precipitated, centrifuged, adsorbed, and separated during extraction and separation. It is removed by one or more than one method to obtain only the nanoclay.

Step (c) is a step of mixing DMSO with the separated nanoclay to produce a nanoclay/DMSO mixture. In this case, the nanoclay may be in the form obtained from the separation step of step (b), in a state in which the dispersion medium is removed or in a state in which the dispersion medium is included. In this case, the DMSO to be mixed with the nanoclay may be pure DMSO (dimethyl sulfoxide), or a solute, solvent, or solution containing 1 wt% or more of DMSO.

The mixing may be performed using a general stirring means, and the temperature during mixing is not limited, but may be generally performed at room temperature.

The mixing ratio of nanoclay/DMSO in step (c) is in the range of 0.01 to 0.99 by weight, preferably 0.2 to 0.8.

The film manufacturing step of (d) is to prepare a nanoclay/DMSO mixture in the form of a film, and one or more processes of filtration, vacuum filtration, hot press, vacuum drying, hot air drying, natural drying, extrusion, injection, and printing can be performed using

After the film manufacturing step in step (d), a drying step of drying the prepared film in the range of -180 to 200°C may be added.

2 schematically illustrates the states of molecules and particles according to each step of the manufacturing process of the present invention. As shown in FIG. 2 , according to the method for manufacturing a solid electrolyte film of the present invention, a structure in which clay and DMSO are arranged through an assembly process such as vacuum filtration is first formed, and a crystallized state is changed through a drying process. .

3 schematically shows the internal structure of a solid electrolyte according to an embodiment of the present invention, schematically illustrating a reaction in which dendrite growth is suppressed, and clay having a high Young's modulus of several tens of GPa has a layered structure. By being present as a unit, the growth of dentrites can be suppressed with the solid electrolyte film of the present invention.

Hereinafter, the present invention will be described in more detail through comparative examples. However, since the configurations described in the embodiments described in this specification are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention, various equivalents and It should be understood that there may be variations.

<Example 1>

1. Preparation of MMT dispersion solution

For liquid exfoliation, 5 g of sodium montmorillonite (Na ⁺ -MMT) (Na-Cloisite, Nanokor Co.) nano clay powder is dispersed in 1 L of distilled water with strong blending for 30 minutes while stirring. The dispersed solution was centrifuged at 2700 g for 15 min to precipitate the unexfoliated MMT particles, and then the supernatant was collected. The supernatant is stable at room temperature for more than several months without noticeable precipitation.

2. Manufacture of MMT/DMSO Composite

For the preparation of MMT/DMSO composite, DMSO was gradually added in an amount of 0, 10, 20, 35, 50% to the volume of the dispersion solution in 20 mL of the 0.5 wt% MMT aqueous dispersion solution, followed by stirring for 30 minutes. to obtain an MMT/DMSO hybrid suspension, and the resulting suspension is self-assembled into an MMT/DMSO composite by filtration through a PTFE membrane (pore size 0.45 μm, Milipore) through a vacuum-assisted filtration process.

Dry the filtered cake and filter membrane together in a convection oven at 60 °C for 6 h to remove water. After drying, the MMT/DMSO composite is easily separated from the membrane as a free-standing film, and MMT, MMT/DMSO-5, MMT/DMSO-10, MMT/DMSO-20, MMT/DMSO-35, MMT/ DMSO-50 was obtained.

The obtained MMT and MMT/DMSO composites have different thickness and properties depending on the relative input amount of DMSO.

<Analysis Example>

The clay/DMSO nanocomposite forms a nacre-mimicking brick structure, showing high ionic conductivity, mechanical strength and thermal stability. The mechanical properties and ionic conductivity, which depend on the specific gravity of MMT and DMSO, reach a mechanical tensile strength of 55.3 ± 4.8 MPa and a mechanical toughness of 210.2 ± 32.6 kJ m ^-2 depending on the conditions, and the ionic conductivity is about 2 × 10 ^- at room temperature. It measures ⁴ S cm ^-1 .

Thermal stability is stable in the range of -100 ~ 120 ℃ as a result of differential thermal analysis.

As a solid electrolyte, NASICON, an inorganic material-based solid electrolyte currently considered the best, has a chemical structure of Na _1+3x Zr ₂ (P _1-x Si _x O ₄ ) ₃ , and is 10 ^-3 S cm ^- It has an ionic conductivity of ¹ . However, it is difficult to use as a flexible battery material based on its fragile mechanical properties, and the high impedance of the interface between the electrode and the electrolyte places great restrictions on electrochemical applications.

As another known solid electrolyte, the widely studied polyethylene oxide-based solid electrolyte is flexible and easy to mass-produce, but it requires a high operating temperature of 65 ~ 78 ℃ to realize ionic conductivity of 10 ^-4 S cm ^-1 . However, it has the disadvantage that mechanical properties and thermal stability are very weak. The solid electrolyte film of the present invention has an ionic conductivity of about 2 × 10 ^-4 S cm ^-1 at room temperature, has a very useful temperature range compared to materials currently being studied as solid electrolytes, and at the same time -100 ~ 120 ℃ It boasts excellent thermal stability over a wide temperature range. In addition, it is flexible and exhibits strong mechanical properties and can be applied to flexible batteries. In addition, the properties that can be decomposed by superworms are properties that cannot be confirmed in previously reported solid electrolytes, and can play a role as an eco-friendly battery material.

One embodiment of the present invention described above should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and it is possible for those of ordinary skill in the art to improve and change the technical idea of the present invention in various forms. Accordingly, such improvements and modifications will fall within the protection scope of the present invention as long as they are apparent to those of ordinary skill in the art.

Claims (9)

An ion conductive solid electrolyte film that mimics the layered structure of an abalone shell cross section,
An ion conductive solid electrolyte film that mimics the layered structure of the abalone shell cross-section, characterized in that clay and DMSO, which are inorganic layered materials, form a brick and mortar structure at the nano level and have ion conductivity at room temperature.
The method of claim 1,
The clay is an ion conductive solid electrolyte film that mimics the layered structure of the abalone shell cross section, characterized in that the clay is at least one of montmorillonite, hectorite, and saponite as an inorganic layered material.
A method for producing an ion conductive solid electrolyte film, the method comprising:
(a) a dispersion step of dispersing the clay in nano units;
(b) a separation step of separating the nanoclay from the clay solution;
(c) mixing nanoclay and DMSO to produce a nanoclay/DMSO mixture;
(d) a film production step of preparing a nanoclay/DMSO mixture in a film form;
4. The method of claim 3,
The dispersing step of (a) is a method of manufacturing an ion conductive solid electrolyte film that mimics the layered structure of the abalone shell cross section, characterized in that the clay is dispersed in nano units by applying a physical force.
4. The method of claim 3,
The dispersing step of (a) comprises dispersing the clay using at least one of ultrasonic dispersion, high-pressure dispersion, blending, and stirring.
4. The method of claim 3,
In the separation step of (b), the clay particles that are not dispersed in nano units are removed by one or more methods of precipitation, centrifugation, adsorption separation, and extraction separation. A method for producing a conductive solid electrolyte film.
4. The method of claim 3,
In the film manufacturing step of (d), one or more processes of filtration, vacuum filtration, hot press, vacuum drying, hot air drying, natural drying, extrusion, injection, and printing are used. A method for manufacturing an ion conductive solid electrolyte film that was simulated.
4. The method of claim 3,
Method for producing an ion conductive solid electrolyte film imitating the layered structure of the abalone shell cross-section, characterized in that it further includes a drying step of drying the prepared film within the range of -180 to 200 ° C after the film production step of (d) .
4. The method of claim 3,
DMSO in step (c) is pure DMSO (dimethyl sulfoxide), or a solute, solvent, or solution containing 1 wt% or more of DMSO. manufacturing method.

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