JP2015165462A - Ion-conducting complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion-conducting complex which can serve as an electrolyte of an electrochemical device or the like and includes a plastic crystal phase, and which enables the elimination of the danger of liquid leakage, the operation in a wide temperature region, and the achievement of a high ion conductivity.SOLUTION: An ion-conducting complex 3 comprises: a structure including insulative porous material particles 1; and an ionic substance 2 held in pores 1a of the particles 1. The ionic substance 2 exhibits a plastic crystal phase. The pores 1a of the particles 1 are meso holes or micropores.

Description

  The present invention relates to an ion conductive composite that is a composite of a structure composed of particles of a porous material having mesopores or micropores and an ionic substance exhibiting a plastic crystal phase. The present invention relates to an ion conductive composite that functions as an electrolyte of an electrochemical device that can operate safely and in a wide temperature range.

  Electrochemical devices such as lithium ion batteries and electric double layer capacitors have used electrolytes in which ionic substances are dissolved in water or organic solvents as electrolytes, or liquids such as ionic liquids. Therefore, in the conventional electrochemical device, it is necessary to securely seal the battery so that there is no liquid leakage.

  On the other hand, ionic substances exhibiting a plastic crystal phase (or a plastic crystal phase) are known. Plastic crystal (or plastic crystal) is an intermediate state between crystal and liquid. The plastic crystal phase is in a solid state in which the three-dimensional arrangement of the molecules or ions constituting it is regular, but the orientation of the molecules or ions is not regular, and the molecules or ions can rotate. It is. Furthermore, the plastic crystal phase can move molecules or ions by hopping conduction through defects. The plastic crystal phase of the ionic substance exhibits high ionic conductivity even though it is a solid because the constituent ions can move by hopping conduction.

  A composite in which a lithium salt is doped in a matrix of a plastic crystal phase is reported in Patent Document 1. In this composite, lithium ions can move relatively freely in the matrix of the plastic crystal phase. Moreover, this composite can be used as an electrolyte of a lithium ion battery while being solid.

Special table 2009-503769 gazette

  Here, it is known that the ionic substance exhibiting the plastic crystal phase described above undergoes transition to the plastic crystal phase when the temperature is raised from the crystalline state. That is, an ionic substance exhibiting a plastic crystal phase exhibits a normal crystal phase at a low temperature, so that there is a problem that the ionic conductivity is greatly reduced at a low temperature and the electrochemical device does not operate. In addition, an ionic substance exhibiting a plastic crystal phase has a problem that the ionic conductivity is lower than that of a liquid, and the efficiency of an electrochemical device is lowered when used as an electrolyte.

  On the other hand, studies have been made to improve the ionic conductivity and lower the transition temperature to the plastic crystal phase by holding an ionic substance exhibiting a plastic crystal phase in the pores of the porous polymer film.

  However, for example, when a porous polymer film having mesopores or micropores is used, the effect of improving the ionic conductivity and lowering the transition temperature does not appear in the electrochemical device because the contact area with the electrode material is small. .

As shown in FIG. 6, an electrochemical device in which an ionic substance exhibiting a plastic crystal phase is held in the pores of the porous polymer film 100 exists as a known technique.
However, in this structure, since there are few contact points of the electrode material 10 and the porous polymer film 100, ions are hardly transmitted and it does not function as an electrochemical device.

  Further, as shown in FIG. 7, there is a known technique in which the space between the electrode material 10 and the porous polymer film 100 is filled with the ion conductive material 6. With this configuration, the device operates as an electrochemical device.

  However, in the configuration shown in FIG. 7, the ion conductive bottleneck becomes the ion conductive material 6. That is, if the ionic substance showing the plastic crystal phase is held in the pores of the porous polymer film 100, the transition temperature to the plastic crystal phase is lowered, but the characteristics of the electrochemical device are the ion conductive substance. Therefore, the effect of lowering the transition temperature cannot be obtained.

  An object of the present invention is to provide an ion conductive composite containing a plastic crystal phase, which has no fear of liquid leakage, can be operated in a wide temperature range, has high ion conductivity, and functions as an electrolyte of an electrochemical device. Is to provide.

As a result of intensive studies to solve the above problems, the present inventors have found a solution means having the following configuration, and have completed the present invention.
(1) A structure composed of particles of an insulating porous material and an ionic substance held in the pores of the particles, wherein the ionic substance exhibits a plastic crystal phase, An ion conductive composite, wherein the pores of the particles are mesopores or micropores.
(2) The ion conductive composite as described in (1) above, wherein the porous material is porous glass.
(3) The ion conductive composite as described in (1) above, wherein the porous material is a porous coordination polymer.
(4) The ion conductive composite according to any one of (1) to (3), wherein the structure is a film or a sheet.
(5) The ion conductive composite according to any one of (1) to (4), wherein the structure is a molded body constituted by a plurality of the particles.
(6) The ion conductive composite according to (5), wherein the molded body has a plurality of gaps provided between the particles.
(7) The ion conductive composite as described in (6) above, wherein an ion conductive material is contained in at least some of the plurality of gaps.
(8) The ion conductive composite according to (7), wherein the ion conductive substance is the same as the ionic substance.

  In the present invention, by introducing an ionic substance exhibiting a plastic crystal phase into mesopores or micropores of particles of an insulating porous material (hereinafter sometimes referred to as porous particles), ions of Disturbed the three-dimensional arrangement. As described above, in the plastic crystal phase, ions can move by hopping conduction through defects. Since defects are introduced at a high concentration in the ionic substance with disordered arrangement, the ionic conductivity can be improved as compared with the case of the ionic substance alone.

  Further, the interaction between ions constituting the crystal is weakened due to the disorder of the arrangement of ions. Therefore, the transition temperature from the crystal phase to the plastic crystal phase can be lowered as compared with the case of the ionic substance alone. That is, according to the present invention, it is possible to stabilize a plastic crystal phase having high ion conductivity up to a lower temperature, and therefore, it can be used as an ion conductor up to a lower temperature.

  Further, by holding the ionic substance in the pores of the porous particles, the contact area with the electrode material can be increased when used as an electrolyte of an electrochemical device such as a battery or an electric double layer capacitor. Therefore, according to the present invention, the above-described effects of improving the ionic conductivity and lowering the transition temperature can be exhibited even when used as an electrolyte of an electrochemical device.

It is a perspective view which shows the ion conductive composite which concerns on one embodiment of this invention, (A) is a figure which shows the state which hold | maintained the ionic substance in the pore of particle | grains, (B) is particle | grains It is a figure which shows the state before hold | maintaining an ionic substance in the pore. It is a cross-sectional schematic diagram at the time of incorporating the ion conductive composite which concerns on one embodiment of this invention as an electrolyte of an electrochemical device. It is a cross-sectional schematic diagram at the time of incorporating the ion conductive composite which concerns on one embodiment of this invention as an electrolyte of an electrochemical device. It is a result of the differential scanning calorimetry in the heating process of an Example. a is Py ₁₂ TFSI @ ZIF-8, b is Py ₁₂ TFSI @ CPG120, and c is Py ₁₂ TFSI alone. It is an Arrhenius plot of the ionic conductivity in the heating process of an Example. a is Py ₁₂ TFSI @ ZIF-8, b is Py ₁₂ TFSI @ CPG120, and c is Py ₁₂ TFSI alone. It is a cross-sectional schematic diagram which shows a part of conventional electrochemical device. It is a cross-sectional schematic diagram which shows a part of conventional electrochemical device.

  Hereinafter, an ion conductive composite according to an embodiment of the present invention (hereinafter sometimes simply referred to as “composite”) will be described with reference to FIGS.

  As shown in FIG. 1, the ion conductive composite 3 includes a structure composed of porous particles 1 and an ionic substance 2, and the ionic substance 2 exhibits a plastic crystal phase, The porous particles 1 are held in the pores 1a. Hereinafter, each component of the composite 3 will be described in order.

  The porous particles 1 are particles of an insulating porous material. The shape of the porous particle 1 is not particularly limited, and may be any shape such as, for example, a sphere, a cube, a rectangular parallelepiped, a regular octahedron, other polyhedrons, a dendritic shape, a needle shape, a rod shape, or a plate shape. That is, the particle in the porous particle 1 is not limited to a spherical shape, and is a concept including shapes other than a spherical shape as long as the effect is not impaired.

  The porous particles 1 have mesopores or micropores 1a. In the catalyst field of the International Union of Applied Chemistry (IUPAC), micropores are defined as pores with a diameter of 2 nm or less. Similarly, pores with a diameter of 2 to 50 nm are mesopores, and pores with a diameter of 50 nm or more are macropores. Is defined.

  The diameter of the pore 1a is preferably 25 nm or less. Thereby, the transition temperature to the plastic crystal phase of the ionic substance 2 can be reduced greatly. Moreover, it is preferable that the diameter of the pore 1a is 0.3 nm or more. This is because it is difficult for ions constituting the ionic substance 2 to be present in the pores 1a smaller than 0.3 nm.

  The diameter of the pore 1a can be determined by, for example, measuring with a gas adsorption method or observing with a SEM or TEM. Further, when the porous particle 1 is composed of a porous coordination polymer described later, it can also be obtained from a crystal structure obtained by X-ray structure analysis. When measuring by the gas adsorption method, the composite 3 is washed with water, methanol, or the like to remove the ionic substance 2 or the adsorbed substance in the pores 1a and heat-treated in a vacuum. What is necessary is just to measure after removing the solvent used for washing | cleaning.

  The pores 1a may form any one-dimensional, two-dimensional, or three-dimensional network, but are particularly preferably three-dimensional. When the pores 1a form a three-dimensional network, the ion conduction path is most reliably constructed. In other words, the ion conduction path is formed isotropically, the interconnection is facilitated, and the ionic conductivity is increased.

  The porous particles 1 are preferably composed of porous glass or a porous coordination polymer. These are all porous materials having mesopores or micropores, and are insulators having no electronic conductivity, so that the composite 3 can be used as an electrolyte of an electrochemical device.

  Further, when porous glass is employed as the porous material, the effects of improving the ionic conductivity and lowering the transition temperature can be obtained. The reason is presumed as follows. In general, the wettability between the glass and the ionic substance 2 is low. Therefore, when the ionic substance 2 takes a crystalline state in the pores 1a, the disorder of the crystal lattice of the ionic substance 2 near the interface becomes particularly large. As a result, the transition temperature from the crystal phase to the plastic crystal phase is greatly reduced. Furthermore, disorder of the crystal lattice facilitates hopping conduction of ions, and the ionic conductivity is improved as compared with the case of the ionic substance 2 alone.

  As the porous glass, a commercially available glass can be used. Specific examples thereof include Vycor (Vycor (registered trademark)) manufactured by Corning, USA, and Controlled Pore Glass (CPG) commercially available from SIGMA-ALDRICH. CPG having a uniform pore diameter is particularly desirable.

  On the other hand, the porous coordination polymer is also called MOF (Metal-Organic Framework) or PCP (Porous Coordination Polymer). The porous coordination polymer has a large number of micropores or mesopore pores 1a and is uniform because the diameter of the pores 1a is determined from the crystal structure. Therefore, the physical properties such as the transition temperature and ionic conductivity of the ionic substance 2 held in the pores 1a become uniform. Furthermore, since the pore 1a of the porous coordination polymer is derived from the crystal lattice as described above, the porous particle 1 having the pore 1a having a uniform pore diameter can be produced with good reproducibility.

  Furthermore, when a porous coordination polymer is adopted as the porous material, the effects of improving the ionic conductivity and lowering the transition temperature can be obtained. The reason is presumed as follows. That is, the porous coordination polymer has pores 1a having extremely small micropores or mesopore regions. For this reason, when the ionic substance 2 is taken into the pores 1a, the disorder of the crystal lattice becomes extremely large. As a result, the transition temperature from the crystal phase to the plastic crystal phase is greatly reduced. Furthermore, since the disorder of the crystal lattice becomes extremely large, hopping conduction of ions becomes easy, and the ionic conductivity is improved as compared with the case of the ionic substance 2 alone.

Examples of porous coordination polymers include:
Zn (MeIM) ₂ (hereinafter referred to as ZIF-8)
Al (OH) (BDC) (hereinafter referred to as Al-MIL-53)
Cr (OH) (BDC) (hereinafter referred to as Cr-MIL-53)
Fe (OH) (BDC) (hereinafter referred to as Fe-MIL-53)
VO (BDC) (hereinafter referred to as V-MIL-47)
Zn ₂ (DOBDC) (hereinafter referred to as Zn-MOF-74)
Mg ₂ (DOBDC) (hereinafter referred to as Mg-MOF-74)
Al (OH) (1,4-NDC)
Cr ₃ O (F, OH) (BDC) ₃ (hereinafter referred to as Cr-MIL-101)
Al ₈ (OH) ₁₅ (BTC) ₃ (hereinafter referred to as Al-MIL-110)
Cu ₃ (BTC) ₂ (hereinafter referred to as HKUST-1)
Zr ₆ O ₄ (OH) ₄ (BDC) ₆ or Zr ₆ O ₆ (BDC) ₆ (hereinafter referred to as UiO-66)
Zr ₆ O ₄ (OH) ₄ (BPDC) ₆ or Zr ₆ O ₆ (BPDC) ₆ (hereinafter referred to as UiO-67)
Zr ₆ O ₄ (OH) ₄ (TPDC) ₆ or Zr ₆ O ₆ (TPDC) ₆ (hereinafter referred to as UiO-68)
ZrO (BDC) (hereinafter referred to as MIL-140)
Etc.

The abbreviations used in the above chemical formula are:
H (MeIM): 2-methylimidazole H ₂ (BDC): terephthalic acid H ₄ (DOBDC): 2,5-dihydroxyterephthalic acid H ₂ (1,4-NDC): 1,4-naphthalenedicarboxylic acid H ₃ ( BTC): 1,3,5-benzenetricarboxylic acid H ₂ (BPDC): 4,4′-biphenyldicarboxylic acid H ₂ (TPDC): H ⁺ dissociated in 4,4 ″ -p-terphenyldicarboxylic acid Represents a residue.

The porous coordination polymer forms a main chain by coordinating an organic ligand to a metal ion. All or part of the organic ligand constituting the porous coordination polymer may be substituted with a ligand having an appropriate functional group (for example, terephthalic acid is substituted with 2-hydroxyterephthalic acid. Such). Examples of the functional group include —OH, —COOH, —NH ₂ , —SO ₃ H, —SO ₃ Li, and —SO ₃ Na. -SO ₃ Li, -SO ₃ Na are especially preferable. This is because when the composite 3 is used as an electrolyte for a battery, lithium ions and sodium ions can be supplied to improve the characteristics of the battery. Further, all or part of the metal ions constituting the porous coordination polymer may be substituted with other metal ions. It is desirable that the metal ions have the same valence.

Further, the porous coordination polymer is required to have resistance to the ionic substance 2. Highly resistant ZIF-8, Al-MIL-53, Fe-MIL-53, Zn-MOF-74, Mg-MOF-74, Al (OH) (1,4-NDC), Cr-MIL-101, Al ₈ (OH) ₁₅ (BTC) ₃ , UiO-66, UiO-67, UiO-68, and MIL-140 are desirable. In particular, ZIF-8, Al-MIL-53, Al (OH) (1,4-NDC), UiO-66, and UiO-67 having high resistance are desirable.

  On the other hand, it is desirable to remove the adsorbed substances present on the surface of the porous particles 1 and in the pores 1a. If the adsorbed substance remains, when the porous particles 1 and the ionic substance 2 are combined, the pore 1a is narrowed or completely blocked by the adsorbed substance, so that the ionic substance 2 is It becomes difficult to inject into 1a. In addition, since the adsorbed substance is mixed as an impurity in the ionic substance 2, the physical properties of the ionic substance 2 may change, and the effect of lowering the transition temperature to the plastic crystal phase may not be obtained. Further, when the composite 3 is used as an electrolyte of an electrochemical device, it causes problems such as gas generation and deterioration of cycle characteristics.

  Examples of the method for removing the adsorbed substance include a method for washing the porous particles 1 with a solvent. The solvent used for washing is preferably water, methanol, THF, or DMF. Water and methanol are particularly desirable. This is because water and methanol have small molecular sizes, so that they easily enter the pores 1a of the porous particles 1 and easily remove the adsorbed substances in the pores 1a. The porous particles 1 may be immersed in a solvent for a long time. The immersion time is desirably 12 hours or more, and more desirably 24 hours or more. In the case of porous glass, it may be washed with an acid such as nitric acid.

  As another method for removing unreacted substances and impurities, there is a method of desorbing an adsorbed substance by heat treatment. In order to remove organic substances, it is desirable to perform heat treatment in air or in an oxygen atmosphere. In the case of a volatile substance, vacuum heat treatment is desirable. The heating temperature is preferably 100 to 300 ° C. A method of completely removing the solvent by performing a heat treatment after washing with the solvent is most desirable.

  In the present embodiment, as described above, the porous particles 1 are made of an insulating material that is insulative, that is, not electronically conductive, and the ionic substance 2 is held inside the pores 1a. Thereby, the composite 3 has ionic conductivity but no electronic conductivity, and can be used as an electrolyte of an electrochemical device such as a battery or an electric double layer capacitor.

  As described above, the ionic substance 2 exhibits a plastic crystal phase. Here, the plastic crystal generally means a phase in which regularity is observed in the three-dimensional arrangement of constituting molecules or atoms, but the orientation of at least one kind of molecule is not regular. In this specification, when it is reported in a paper or the like that a substance alone exhibits a plastic crystal phase, it is expressed as indicating a plastic crystal phase.

  Examples of the cation of the ionic substance 2 include pyrrolidinium ion, quaternary ammonium ion, piperidinium ion, and quaternary phosphonium ion. Alkali metal salts such as lithium salts and sodium salts, and alkaline earth metal salts such as magnesium salts may be used. Among these, pyrrolidinium ions and quaternary ammonium ions having a low transition temperature to the plastic crystal phase and high ion conductivity are particularly preferably used.

Examples of the anion include halogen such as Cl ⁻ and Br ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , [FSO ₂ NSO ₂ F] ⁻ (FSI), and [CF ₃ SO ₂ NSO ₂ CF ₃ ]. _{^{- (TFSI), [C 2}} F 5 SO 2 NSO 2 C 2 F 5] - (BETI), ClO 4 - and the like. Among these, TFSI having a low transition temperature to the plastic crystal phase and high ion conductivity is particularly preferably used.

  These exemplified ionic substances 2 are particularly preferably used as a battery electrolyte in which a lithium salt, a sodium salt, and a magnesium salt are mixed.

  Examples of the method for injecting the ionic substance 2 into the pores 1a include a method in which the porous particles 1 and the ionic substance 2 are mixed and allowed to stand at a temperature equal to or higher than the melting point of the ionic substance 2. . In order to promote the diffusion of the ionic substance 2 into the pores 1a, the heating temperature is desirably 50 to 100 ° C. higher than the melting point of the ionic substance 2. This is because the diffusion rate of the ionic substance 2 increases as the temperature increases, while the porous particles 1 are decomposed or the ionic substance 2 evaporates or decomposes when the temperature is too high. The standing temperature is appropriately adjusted by the combination of the porous particles 1 and the ionic substance 2.

  The heating time is preferably within 100 hours, particularly preferably within 24 hours. This is because if the heating time is too long, the porous particles 1 are easily decomposed and the ionic substance 2 is easily evaporated or decomposed. The shorter the moving distance until the ionic substance 2 reaches the center of the porous particle 1 through the pores 1a, the more reliably the ionic substance 2 can be injected into the pores 1a. The particle diameter of the porous particles 1 is desirably 500 μm or less in the case of porous glass, and 1 μm or less in the case of a porous coordination polymer. The larger particle diameter of the porous glass can be tolerated because the porous glass generally has a larger pore diameter than the porous coordination polymer, and the ionic substance 2 can be easily diffused.

  In order to prevent adsorption of gas, particularly moisture, to the pores 1a and the ionic substance 2, the ionic substance 2 is injected into the porous particles 1 in, for example, a vacuum or a dry atmosphere with a dew point of −20 ° C. or lower. It is preferable to carry out in the inside. Further, in order to suppress chemical reactions such as oxidation and reduction of the porous particles 1 and the ionic substance 2, it is more preferable to perform the implantation treatment in a vacuum or in an inert gas atmosphere such as nitrogen gas or argon gas.

  The mixing ratio of the porous particle 1 and the ionic substance 2 is preferably mixed so that the total volume of the pores 1a contained in the porous particle 1 and the volume of the ionic substance 2 are equal. You may mix in the ratio from which the substance 2 becomes less and excess with respect to the whole volume of the pore 1a. However, even when the ionic substance 2 becomes too small, the volume of the ionic substance 2 with respect to the total volume of the pores 1a is preferably 20% or more, more preferably 50% or more, and further preferably 75% or more. It is. As the amount of the ionic substance 2 is smaller, the path of the ionic substance 2 is more likely to be interrupted, and the ionic conduction may be interrupted. Moreover, when the ionic substance 2 becomes excessive, it is preferable that the ionic substance 2 volume with respect to the whole volume of the pore 1a is less than 200% (2 times). For the purpose of lowering the transition temperature to the plastic crystal phase, if it becomes 200% (2 times) or more, the excess ionic substance 2 covers the outer periphery of the porous particle 1, and the ionic conductivity of the composite 3 is The rate is limited by the ionic substance 2 existing outside the pores 1a. In this case, in particular, even if the ionic substance 2 in the pore 1a is a plastic crystal phase, in the temperature range where the excess ionic substance 2 existing outside the pore 1a becomes a crystalline phase, the ions of the composite 3 The conductivity is limited by the ionic substance 2 in the crystalline state. Therefore, there is a possibility that the effect of lowering the transition temperature of the ionic substance 2 to the plastic crystal phase by holding the ionic substance 2 in the pores 1a may not be obtained.

  The fact that the ionic substance 2 is held inside the pores 1a of the porous particles 1 means that, for example, a differential scanning calorimetry (DSC) of the ionic substance 2 alone and the composite 3 is performed, and the crystal phase and the plastic crystal phase What is necessary is just to confirm whether the appearance temperature of the exothermic or endothermic peak resulting from the phase transition between the ionic substance 2 and the composite 3 is different. The composite 3 may not show any exothermic or endothermic peak. Or when the ionic substance 2 exists excessively with respect to the volume of the pore 1a of the porous particle 1, the same transition temperature as the case of the ionic substance 2 alone may be shown. In such a case, the composite 3 is evaluated while changing the measurement temperature by a method such as solid nuclear magnetic resonance (NMR) analysis or an alternating current impedance method, and is higher than the phase transition temperature in the case of the ionic substance 2 alone. By confirming the presence or absence of the phase transition behavior at a low temperature, it can be determined whether or not the ionic substance 2 is present in the pores 1 a of the porous particles 1.

  The kind and composition of the porous particles 1 and ionic substances 2 to be used are specified by, for example, elemental analysis, X-ray diffraction (XRD) measurement, nuclear magnetic resonance (NMR) analysis, infrared absorption analysis (IR), or the like. That's fine.

  Moreover, the composite 3 may contain an organic solvent. That is, the composite 3 may further contain an organic solvent in the pores 1a. When the organic solvent is dissolved in the ionic substance 2, the dissociation degree of the ionic substance 2 is improved, and the ionic conductivity is improved. This is because the organic solvent coordinates with the ions constituting the ionic substance 2 to form a solvate and facilitate the dissociation of the cation and the anion.

  As an organic solvent, what contains an oxygen atom in a molecule | numerator is desirable. This is because an organic molecule containing an oxygen atom has a large polarity, so that it is easy to form a solvation with ions, and the ionic conductivity is particularly improved. Ethylene carbonate, propylene carbonate, γ-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, diglyme, triglyme, and tetraglyme are preferable because they easily form solvates with ions and improve ionic conductivity. Since it is easy to introduce into the pores 1a of the porous particles 1, those having a linear molecular structure are desirable, and diglyme, triglyme and tetraglyme are particularly desirable.

  On the other hand, the structure constituted by the porous particles 1 is preferably in the form of a film or a sheet. With these shapes, the ion conduction path is shortened, and the characteristics of the electrochemical device are improved. Examples of the other shape of the structure include a particle shape, a wire (wire) shape, a rod (bar) shape, and a bulk shape.

  The structure is obtained by pressure-molding the porous particles 1 by a known method such as uniaxial pressing, isostatic pressing, roller rolling, or extrusion molding. Alternatively, the structure can also be obtained by molding a slurry in which the porous particles 1 are dispersed in a solvent by a known sheet molding method such as tape casting, slip casting, spin coating, and the like, and drying.

  The structure can be used as an electrolyte of an electrochemical device, for example, as a molded body 4 formed as shown in FIG. The molded body 4 is composed of a plurality of porous particles 1. According to such a configuration, the following effects can be obtained.

  The electrode 20 of the electrochemical device is generally composed of an aggregate of a plurality of particulate electrode materials 10. Therefore, fine irregularities are formed on the surface of the electrode 20 by the electrode material 10. Since the porous particles 1 constituting the molded body 4 of the present embodiment are in the form of particles, they enter into the irregularities of the electrode 20, and the number of contact points between the electrode material 10 and the molded body 4 increases. As a result, ion transmission is smooth, and in the case of a battery, the output density is improved. In the case of an electric double layer capacitor, since the number of ions near the electrode surface increases, the capacity increases. Further, since the ionic substance 2 is held in the pores 1a of the porous particles 1, the transition temperature to the plastic crystal phase is lowered, so that the performance of the battery or the electric double layer capacitor is maintained even at a low temperature. .

  A plurality of gaps 5 are formed between the porous particles 1 and 1 adjacent to each other. In other words, the molded body 4 has a plurality of gaps 5 provided between the porous particles 1 and 1. According to such a configuration, the following effects can be obtained. That is, in the case of a battery, there are many cases where the electrode material 10 expands and contracts due to charge and discharge. By forming the gap 5, deformation due to expansion / contraction can be mitigated.

  As shown in FIG. 3, an ion conductive material 6 may exist in the gap 5. Due to the presence of the ion conductive material 6, the conduction of ions between the porous particles 1 and 1 adjacent to each other becomes smooth, and the characteristics of the electrochemical device are improved. FIG. 3 illustrates the case where the plurality of gaps 5 are all occupied by the ion conductive material 6, but a part of the plurality of gaps 5 may be occupied by the ion conductive material 6. .

  Examples of the ion conductive material 6 include water, an organic electrolyte, and an ionic liquid. In particular, the ion conductive material 6 is desirably the same as the ionic material 2 described above. In other words, the ion conductive material 6 is desirably the same material as the ionic material 2. This is because if the same substance is used, ion conduction becomes smoother. Further, it is possible to avoid changes in physical properties due to mutual diffusion of the ion conductive material 6 and the ionic material 2.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.

The following two types of commercially available particles were used.
ZIF-8: Basolite (registered trademark) Z1200 (pore diameter 1.2 nm) of SIGMA-ALDRICH, a porous coordination polymer
CPG120: SIGMA-ALDRICH Controlled Pore Glass (pore size 12 nm, 80-120 mesh) which is a porous glass

  Using ZIF-8 and CPG120, a complex was prepared as follows. First, ZIF-8 and CPG120 powder were heated at 150 ° C. for 12 hours while evacuating to remove adsorbed substances in the pores. In order to prevent moisture and the like from adsorbing again into the pores, ZIF-8 and CPG120 were brought into a glove box with a dew point of −20 ° C. or lower filled with argon gas. And the powder of ZIF-8 and CPG120 which is a particulate-form structure, and the ionic substance were mixed.

As the ionic substance, 1-ethyl-1-methylpyrrolidinium bis (trifluoromethanesulfonyl) imide (hereinafter referred to as Py ₁₂ TFSI) was used. The fact that Py ₁₂ TFSI exhibits a plastic crystal phase is reported, for example, in DR MacFarlane et al., Nature 402, 792-794 (1999). The mixing ratio was such that the weight ratio of ZIF-8 to Py ₁₂ TFSI was 10: 9, and the weight ratio of CPG 120 to Py ₁₂ TFSI was 10: 7. All of these mixing ratios are such that the volume of Py ₁₂ TFSI with respect to the total volume of the pores of the porous particles is 100%.

A mixture of the ZIF-8 and CPG120 powder and the ionic substance was subjected to a heat treatment at 200 ° C. for 12 hours in an argon gas atmosphere to obtain each composite. Hereinafter, each composite obtained, referred to as _{Py 12 TFSI @ ZIF-8,} Py 12 TFSI @ CPG120.

FIG. 4 shows the differential scanning calorimetry (DSC) of each complex obtained and Py ₁₂ TFSI alone. Although the measurement was performed at −150 to 200 ° C., only the heating process at −50 to 100 ° C. is shown in FIG. The heating and cooling rate is 5 ° C./min.

As shown in c in FIG. 4, in the case of Py ₁₂ TFSI alone, a sharp endothermic peak is observed at 15 and 89 ° C. It is considered that 89 ° C. is melting and 15 ° C. is endotherm accompanying the transition to the plastic crystal phase.

On the other hand, as shown by b in FIG. 4, Py ₁₂ TFSI @ CPG120 has a broad endothermic peak having an apex at 4 ° C. and a relatively sharp endothermic peak at 64 ° C. It is considered that 64 ° C. is melting and 4 ° C. is endotherm accompanying the transition to the plastic crystal phase. That is, by maintaining Py ₁₂ TFSI in the pores of CPG 120, not only the melting point was lowered by 25 ° C. but also the transition temperature to the plastic crystal phase could be lowered by 11 ° C.

Further, as shown in a in FIG. _{4, Py 12 TFSI @ ZIF-} 8 has a distinct endothermic peak was observed at -150~200 ℃. ZIF-8 has 1/10 size pores of CPG120. Therefore, when Py ₁₂ TFSI is taken into the pores of ZIF-8, the crystal lattice of Py ₁₂ TFSI is greatly disturbed. As a result, it is considered that the transition temperature from the crystal phase to the plastic crystal phase was lowered to a DSC measurement temperature range or lower.

In the case of any of the _{Py 12 TFSI @ CPG120, Py 12} TFSI @ ZIF-8 also peak did not appear at the same temperature as that of Py ₁₂ TFSI alone. If Py ₁₂ TFSI remains in the pores without being taken up, a peak should appear at the same position as in the case of Py ₁₂ TFSI alone in each composite. From the above results, it is considered that in the produced Py ₁₂ TFSI @ CPG120 and Py ₁₂ TFSI @ ZIF-8, all Py ₁₂ TFSI was taken into the pores.

  Next, the ionic conductivity of each composite was evaluated. First, a sample was obtained by press molding with carbon paper having irregularities pressed on both sides of each composite. This sample has a configuration in which an electrode having irregularities is brought into contact with both surfaces of a circular tablet mold obtained by compressing powder. Next, this sample was sandwiched between stainless steel (SUS) electrodes, and the ionic conductivity was evaluated by an AC impedance method in a dry argon gas atmosphere. The measurement frequency is 1 Hz to 1 MHz. FIG. 5 shows the temperature dependence of ionic conductivity.

As shown by b and c in FIG. 5, Py ₁₂ TFSI @ CPG120 has lower ionic conductivity than Py ₁₂ TFSI alone at a low temperature, but it reverses in a temperature range of 5 ° C. or higher and is 50 ° C. or higher. In the temperature range, the ion conductivity was higher by one digit or more. As evaluated by DSC, Py ₁₂ TFSI @ CPG120 has a transition temperature of 4 ° C in the plastic crystal phase, which is lower than that of Py ₁₂ TFSI alone. It is considered that the ionic conductivity was higher than that of Py ₁₂ TFSI alone. Moreover, it is considered that the fact that the disorder of the crystal lattice of Py ₁₂ TFSI increases near the interface between CPG 120 and Py ₁₂ TFSI supports high ionic conductivity.

On the other hand, according to the DSC evaluation results described above, it is considered that Py ₁₂ TFSI @ ZIF-8 has a transition temperature to a plastic crystal phase that has been lowered to a DSC measurement temperature range or lower. As a result, as shown by a and c in FIG. 5, Py ₁₂ TFSI @ ZIF-8 can maintain the plastic crystal state in the entire temperature range of the ionic conductivity measurement. _{12 It} is considered that the ionic conductivity was higher than that of TFSI alone. In addition, it is considered that due to the small pore diameter of ZIF-8, a large amount of crystal lattice disturbance was introduced into Py ₁₂ TFSI in the pores of ZIF-8 and high ionic conductivity was expressed.

DESCRIPTION OF SYMBOLS 1 Porous particle 1a Pore 2 Ionic substance 3 Ion conductive composite 4 Molded body 5 Gap 6 Ion conductive substance 10 Electrode material 20 Electrode 100 Porous polymer membrane

Claims (8)

A structure composed of particles of an insulating porous material, and an ionic substance held in the pores of the particles,
The ionic substance exhibits a plastic crystal phase,
An ion conductive composite, wherein the pores of the particles are mesopores or micropores.   The ion conductive composite according to claim 1, wherein the porous material is porous glass.   The ion conductive composite according to claim 1, wherein the porous material is a porous coordination polymer.   The ion conductive composite according to claim 1, wherein the structure is in the form of a film or a sheet.   The ion conductive composite according to any one of claims 1 to 4, wherein the structure is a molded body composed of a plurality of the particles.   6. The ion conductive composite according to claim 5, wherein the molded body has a plurality of gaps provided between the particles.   The ion conductive composite according to claim 6, wherein an ion conductive material is contained in at least a part of the plurality of gaps.   The ion conductive composite according to claim 7, wherein the ion conductive material is the same as the ionic material.

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