JP2022031092A - Polymer electrolyte - Google Patents

Abstract

To provide a polymer electrolyte that exhibits good ion conductivity even in a room temperature environment and has excellent productivity.SOLUTION: The polymer electrolyte includes: an alkali metal salt; a dissociation auxiliary agent; and polyarylene sulfide, where the polyarylene sulfide is a polyarylene sulfide copolymer composed of a constitutional unit represented by the formula: -(Ar-S)-, where Ar has a constitutional unit represented by a predetermined chemical formula, and at least one constitutional unit selected from the group consisting of other predetermined chemical formulae. The predetermined chemical formula has two substituent groups selected from an alkyl group, an alkoxy group, an amino group, and a hydroxyl group, and the other predetermined chemical formulae have two or more substitutional groups selected from hydrogen, an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group.SELECTED DRAWING: None

Description

The present invention relates to polymer electrolytes.

In recent years, alkaline secondary batteries such as lithium secondary batteries are being used in various applications such as smartphones, mobile devices such as mobile phones, hybrid vehicles, electric vehicles, and household power storage batteries, and research and development on them has been carried out. It is actively done.

Lithium secondary batteries are strongly required to have improved safety, especially in applications such as electric vehicles. Since the conventional electrolytic solution battery uses a flammable electrolytic solution, the battery may burn or explode. Therefore, research on solid electrolytes that can contribute to improving safety is becoming active.

The solid electrolyte is a solid that easily conducts ions, and the solid electrolyte is generally classified into an oxide type, a sulfide type, and a polymer type. Polymer-based solid electrolytes are attracting attention because of their advantages such as productivity and flexibility, but their ionic conductivity at room temperature is low, and a solution is required.

In recent years, among polymer-based solid electrolytes, polyphenylene sulfide (hereinafter abbreviated as PAS) -based electrolytes represented by polyphenylene sulfide (hereinafter abbreviated as PPS) have been attracting attention in terms of flame retardancy and mechanical properties. As in Patent Document 1, it is known that PPS is a conjugated polymer and can be electron-conducted by adding an electron-accepting dopant. However, in recent years, electrons have been added to a mixture of PPS and an alkali metal salt. Acceptor-doped solid electrolytes are disclosed in Patent Documents 2-4. Further, in Patent Documents 2 to 4, the PPS solid electrolyte is produced by a method of mixing PPS, an alkali metal salt, an electron-accepting dopant and the like at a high temperature and then molding the PPS solid electrolyte.

Further, a method of improving ionic conductivity by containing an electrolytic solution in a solid electrolyte polymer is known (Patent Documents 5 to 6). The electrolyte produced by the above method is called Polymer Matrix Electrolyte (PME).

JP-A-59-157151 U.S. Patent Application Publication No. 2018/006308 Chinese Patent Application Publication No. 106450424 U.S. Patent Application Publication No. 2017/0005356 Taiwan Patent Application Publication No. 201015279 U.S. Patent Application Publication No. 2006/01777440

Patent Documents 2 to 4 show that high crystallinity of a solid electrolyte containing PPS is important for ionic conductivity, and a solid electrolyte using PPS having a high crystallinity is disclosed. .. However, when PPS with a high degree of crystallinity is used, it must be processed at a high temperature of around 300 ° C., which causes deterioration of contained components such as lithium salts and dopants, resulting in deterioration of ionic conductivity at room temperature and poor quality. May cause stabilization. In addition, the inclusion of an electron-accepting dopant may cause the polymer matrix to cause deterioration of mechanical properties such as oxidative deterioration and embrittlement. Further, when the solid electrolyte is produced, if the mechanical properties are deteriorated due to high temperature processing, the film may be cracked or collapsed during the film formation, which poses a problem in productivity. In Patent Documents 5 to 6, since the solvent casting method is used when producing PME, a step of evaporating the solvent is required in the process of producing PME, and there is a problem in productivity. Further, while the solvent for dissolving the polymer does not contribute to the improvement of the conductivity of the polymer electrolyte, there is a problem that the raw material cost increases and the productivity decreases. In addition, the evaporated solvent may dissipate into the environment, which poses a problem in environmental suitability. From the above viewpoint, the conventional PME electrolyte has problems in productivity and environmental suitability.

Further, the polyimide (PI) described in Patent Document 6 has a problem that it easily absorbs moisture as a base material of a polymer electrolyte. When the polymer electrolyte contains water as an ionizing aid, moisture absorption may change the ratio of the components of the polymer electrolyte, which lowers the potential window of the polymer electrolyte and facilitates electrolysis of water. Sometimes. On the other hand, in the case of a polymer electrolyte containing an organic solvent as an ionization aid, deterioration such as electrolysis of the ionization aid due to moisture absorption occurs. From the above point of view, there is a problem in storage and storage. Further, a general PI base material has a problem that the potential window for electrolysis is less than 2 V, and it is difficult to apply it to high voltage battery applications.

As a result of diligent studies to solve this problem, the present invention is a polymer that exhibits good ionic conductivity at room temperature, has low hygroscopicity, and is excellent in productivity, environmental suitability, wide potential window, and the like. We found an electrolyte and came up with the present invention.

That is, in order to solve the above problems, the present invention has the following configuration.

(1) A polymer electrolyte containing an alkali metal salt, an ionizing aid and a polyarylene sulfide, wherein the polyarylene sulfide is a polyarylene sulfide copolymer having the formula- (Ar—S) — as a constituent unit. , Ar is a polymer electrolyte having a structural unit represented by (A) of the chemical formula (1) and at least one structural unit selected from the group consisting of (B) to (G) of the chemical formula (1).

(R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are hydrogen and alkyl groups. It is a substituent selected from an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is selected from an alkylene group, O, CO, SO, and SO _2. )
(2) The ionization aid has an ion dissociation degree (1-ξ) obtained by the formula (1) at 25 ° C. of 0.1 or more and a solvent diffusion coefficient obtained by the formula (2) of 15 or less. The polymer electrolyte according to (1), which contains one or more solvents.

(3) The above-mentioned ionizing aid is at least water, γ-butyrolactone, N-methylpyrrolidone (NMP), butylene carbonate (BC), ethylene carbonate (EC) propylene carbonate (PC), methyl-γ-butyrolactone (GVL), triglycrim. The polymer electrolyte according to (1) to (2), which comprises one or more selected from (TG), diglycyl (DG), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC).

(4) The polymer electrolyte according to (1) to (3), wherein the alkali metal salt contains one or more LIFSI and LITFSI.

(5) A battery having the polymer electrolyte according to any one of (1) to (4).

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polymer electrolyte having a wide potential window, which exhibits good ionic conductivity even at room temperature, has low hygroscopicity, and is excellent in productivity and environmental suitability.

(Definition of polymer electrolyte)
The polymer electrolyte of the present invention refers to a substance having a polymer matrix and easily moving ions by applying an electric field from the outside. The polymer electrolyte contains an ionizing aid described later. The ease of movement of alkali metal ions in the polymer electrolyte of the present invention can be determined by the ion diffusion coefficient at 25 ° C. The ion diffusion coefficient (m ² / s) of an alkali metal ion may be measured by nuclear magnetic resonance spectroscopy (NMR) of the ion.

Further, since the ion diffusion coefficient measured by NMR may take a plurality of values even under the same temperature condition, the ion diffusion coefficient in the present invention means the maximum value of the ion diffusion coefficient of the ion at 25 ° C. From the viewpoint of ionic conductivity, the ion diffusion coefficient of the polymer electrolyte of the present invention at 25 ° C. is preferably ^10-13 m ² / s or more, more preferably ^10-12 m ² / s or more. It is more preferably ^-11 m ² / s or more. In addition, the polymer electrolyte of the present invention contains an alkali metal salt, an ionizing aid and polyarylene sulfide (hereinafter, may be referred to as PAS). Hereinafter, alkali metal salts, ionizing aids and PAS will be described.

(Alkali metal salt)
It is important that the polymer electrolyte of the present invention contains an alkali metal salt from the viewpoint of ionic conductivity. The alkali metal salt in the present invention refers to a salt containing an alkali metal ion as a constituent ion. Examples thereof include metal salts containing lithium metal ions, sodium metal ions, potassium metal ions and the like. From the viewpoint of ion diffusivity, metal ions having a small ion diameter are preferable.

The anion is preferably a soft base based on the HSAB rule because of its high dissociability to ions, and is preferably a bis (trifluoromethanesulfonyl) imide anion or a bis (fluorosulfonyl) imide anion. That is, the alkali metal salt preferably contains at least one of lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethane) sulfonimide.

The HSAB rule (Principle of Hard and Soft Acids and Bases) is based on R.M. G. The acid-base strength proposed by Pearson is classified from the viewpoint of being hard and soft. Hard acids have a high affinity for hard bases, and soft acids have a high affinity for soft bases. Hard acids are those in which the atom that becomes an electron acceptor is small, does not have valence electrons that enter an orbit that easily deforms, and has a large positive charge. A soft acid has a large atom that becomes an electron acceptor, has valence electrons that enter an orbit that easily deforms, and is small even if it has no charge. A hard base is a base in which valence electrons are strongly bonded to an atom, and a soft base is a base in which valence electrons are easily polarized. The HSAB rule and the acid-base classification of HSAB are described in R.I. B. Heslop and K. It is described in Section 15 of Acid-Bases in Chapter 9 of "Inorganic Chemistry-A Guide to Advanced Study" by Jones.

Specifically, the alkali metal salt preferably contains lithium salts and sodium salts, such as lithium hydroxide (LiOH), lithium carbonate (LiCO ₃ ), lithium perchlorate (LiClO ₄ ), and lithium tetrafluoroborate. (LiBF ₄ ), Lithium hexafluorophosphate (LiPF ₆ ), Lithium bis (fluorosulfonyl) imide (LiFSI), Lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), Lithium bis (oxalate) borate (LiBOB), 6 Sodium fluoride phosphate (NaPF ₆ ), sodium tetrafluoroborate (NaBF ₄ ), sodium perchlorate (NaClO ₄ ), sodium bis (fluorosulfonyl) imide (NaFSI), and sodium bis (trifluoromethanesulfonyl) imide. It is more preferable to contain one or more selected from (NaTFSI), and further preferably to contain LiTFSI and one or more obtained from LiFSI from the viewpoint of high ion dissociation.

Further, the alkali metal salt may be used by mixing a plurality of kinds of salts in an appropriate ratio.

From the viewpoint of ionic dissociation and ionic conductivity, the molar ratio of all structural units and alkali metal salts in the polymer is preferably 100: 2 to 100: 400, more preferably 100: 2 to 100: 100. More preferably, 100: 2 to 100: 50.

(Ionization aid)
The ionizing aid contained in the polymer electrolyte of the present invention contains a solvent. From the viewpoint of the dissociation of the alkali metal salt and the ionic conductivity, it is important that this solvent is as follows. That is, this solvent has an ion dissociation degree (1-ξ) obtained by the formula (1) at 25 ° C. of 0.1 or more, and a solvent diffusion coefficient (Dsolvent) obtained by the formula (2) of 15. It is as follows.

The degree of ion dissociation (1-ξ) obtained by the formula (1) may vary depending on the ionizing aid, temperature, ion concentration, and ion type. Here, the degree of ion dissociation refers to the degree of ion dissociation when the temperature is 25 ° C., the ion concentration is 0.2 mol / L, the cation is lithium ion, ^and the anion is N (SO ₂ CF ₃ ) _2- .

The notations of the equations (1) and (2) represent the following numerical values. σ _imp : Ion conductivity, e ₀ : Electron power, N: Avogadro constant, k: Boltzmann constant, T: Temperature, D _Lithium : Mass diffusivity of lithium ions, D _Anion : N (SO ₂ CF ₃ ) ₂ ^- Diffusion Coefficient, (1-ξ): Ion dissociation degree, D _solvent : Solvent diffusion coefficient, _c : Boundary condition constant, η: Viscosity, ra: Diffusivity radius.

The ionizing aid can bind to lithium ions at the interface of the polymer electrolyte or at the non-crystalline portion to form a third phase having better ionic conductivity than the polymer matrix. The third phase forms a conductive passage and can improve the ionic conductivity of the polymer electrolyte.

The degree of ion dissociation (1-ξ) obtained by the formula (1) indicates the rate of ion dissociation. From the viewpoint of promoting the dissociation of the alkali metal salt, the ion dissociation degree (1-ξ) obtained by the above solvent formula (1) is preferably 0.1 or more.

Further, the solvent diffusion coefficient (Dsolvent) obtained by the formula (2) indicates the viscosity of the solvent, and the lower the value, the higher the ionic conductivity of the alkali metal ion tends to be. From the above viewpoint, the solvent diffusion coefficient (Dsolvent) obtained by the above solvent formula (2) is preferably 15 or less.

From the above viewpoint, a solvent having an ion dissociation degree (1-ξ) obtained by the ionization aid formula (1) of 0.1 or more and a solvent diffusion coefficient (Dsolvent) of 15 or less obtained by the formula (2). It is preferable to contain one or more.

From the same viewpoint, the above-mentioned ionizing aids include water, γ-butyrolactone (GBL), n-methylpyrrolidone (NMP), butylene carbonate (BC), ethylene carbonate (EC) propylene carbonate (PC), and methyl-γ. -It is preferable to contain one or more selected from the group consisting of butyrolactone (GVL), triglym (TG), diglym (DG), ethylmethyl carbonate (EMC), and dimethyl carbonate (DMC). Among them, from the viewpoint of the potential window of the electrolyte, the ionization aid preferably contains at least one of γ-butyrolactone (GBL) and n-methylpyrrolidone (NMP), and more preferably the above-mentioned polymer. From the viewpoint of affinity with the above-mentioned ionizing aid, it is most preferable that the ionizing aid contains γ-butyrolactone (GBL).

(Polyarylene sulfide)
PAS (the arylene group is abbreviated as "Ar") in the present invention is a polymer having the formula- (Ar-S)-as a constituent unit. Further, Ar of the above-mentioned structural unit- (Ar-S)-is at least one selected from the group consisting of the structural unit of (A) of the chemical formula (1) and (B) to (G) of the chemical formula (1). It has two building blocks. From the viewpoint of controlling the melting point and the molecular weight, it is particularly preferable that Ar has the structural unit of the chemical formula (1) (B) or the structural unit of the chemical formula (1) (C).

(R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are hydrogen and alkyl groups. It is a substituent selected from an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is selected from an alkylene group, O, CO, SO, and SO _2. )
Further, for 1 mol of the constituent unit represented by-(Ar-S)-, Ar of the copolymerization unit (-(Ar-S)-is from the group consisting of (B) to (G) of the chemical formula (1). Those having at least one constituent unit selected are preferably 1 mol% or more and 50 mol% or less, more preferably 3 mol% or more and 30 mol% or less, and even more preferably 5 mol% or more and 25 mol% or less. When the copolymerization unit is 1 mol% or more, the melting point of PAS is greatly lowered, the processing temperature when producing a solid electrolyte can be lowered, and the ionic conductivity and quality stability of the polymer electrolyte can be improved. On the other hand, when the content is 50 mol% or less, the PAS copolymer tends to be efficiently recovered when it is recovered from the reaction solution after the polymerization reaction of the PAS copolymer is completed. , The content ratio of the copolymerization unit in the PAS copolymer is added as a copolymerization component with respect to the total amount of the dihalogenated aromatic compound represented by (A') to (G') of the chemical formula (2) added at the time of polymerization. It is the same as the ratio of the addition amount of the compounds (B') to (G').

As long as the unit represented by-(Ar-S)-is the main constituent unit, the branching unit or the cross-linking unit represented by (H) to (J) of the following chemical formula (3) can be included. The copolymerization amount of these branching units or cross-linking units is preferably in the range of 0 to 1 mol% with respect to 1 mol of the constituent unit represented by − (Ar—S) −.

Further, the PAS copolymer in the present invention may be any of a random copolymer, a block copolymer and a mixture thereof.

The method for synthesizing the PAS copolymer for a solid electrolyte of the present invention is not particularly limited, and is obtained by reacting a sulfidizing agent with a dihalogenated aromatic compound in an organic polar solvent, or a diodeo aromatic compound and sulfur. Examples thereof include a method of melting and reacting the above in a solvent-free manner, but it is preferable to adopt the former polymerization method, which is industrially produced, from the viewpoint of versatility.

(Crystallinity)
Here, the crystallinity of the polymer electrolyte means the crystallinity in a state where the ionizing aid is not contained. From the viewpoint of melting point, processability and impregnation of the ionizing aid, the polymer electrolyte of the present invention preferably has a crystallinity of 20% or less of the polymer contained in the polymer electrolyte of the present invention.

The degree of crystallinity generally refers to the proportion of the crystal region in the entire polymer, but here, the amount of heat of crystal melting of the polymer electrolyte before impregnation with the ionizing aid is the amount of heat of melting of the paraphenylene sulphide complete crystal (146). The value divided by .2 J / g) is regarded as the crystallinity of the polymer.

In Patent Document 1 and the like, it is known that high crystallinity of a polymer electrolyte is important for ionic conductivity, but lowering the crystallinity tends to lower the melting point of the polymer. It can be processed at low temperature, decomposition of lithium salt, oxidation of polymer, cross-linking, etc. are suppressed, compatibility with ionizing aids is high, and conductive passages are easily formed, so even with low crystallinity. High ionic conductivity can be reached.

Also, if the crystallinity is low, the temperature required to mold the polymer electrolyte will be low. In particular, when a component such as an alkali metal salt is contained, the mixing and molding processes of the components can be performed continuously or simultaneously.

From the above viewpoint, the crystallinity of the polymer electrolyte in the present invention is preferably 20% or less, more preferably 15% or less. Further, the crystallinity of the polymer electrolyte in the present invention can be measured by a differential scanning calorimeter (DSC). Specifically, the polymer electrolyte is heated from 25 ° C. to 120 ° C. at a rate of 10 ° C./min under a nitrogen atmosphere and held at 120 ° C. for 2 hours. After that, the temperature was raised to 400 ° C. at a rate of 10 ° C./min, and among the obtained endothermic peaks, the peak having the widest area was regarded as the melting peak, and the amount of heat of melting (J / g) obtained from the melting peak area was 146. The value divided by 2 (J / g) is defined as the crystallinity (%).

(Melting point)
The melting point of the polymer electrolyte referred to here is the melting point in a state where the ionizing aid is not contained. The melting point of the polymer electrolyte is preferably 200 ° C. or higher and 320 ° C. or lower from the viewpoint of formability, productivity, and quality stability. Due to the low melting point of the polymer electrolyte, it can be mixed at a lower temperature, and sublimation and deterioration of the raw material can be prevented. Further, when there is a raw material that easily sublimates in a molten state, it is necessary to mix each raw material and the polymer in order to prevent sublimation. However, since the melting point of the polymer electrolyte is low, it can be melt-mixed at once. This can simplify the process. From the above viewpoint, the melting point of the polymer electrolyte in the present invention is preferably 200 ° C. or higher and 320 ° C. or lower, more preferably 200 ° C. or higher and 280 ° C. or lower, and 200 ° C. or higher and 250 ° C. or lower. Is even more preferable. The melting point of the polymer electrolyte in the present invention is measured as follows. The polymer electrolyte is heated from 25 ° C. to 120 ° C. at a rate of 10 ° C./min under a nitrogen atmosphere and held at 120 ° C. for 2 hours. After that, the temperature is raised to 400 ° C. at a rate of 10 ° C./min, and among the obtained endothermic peaks, the peak having the widest area is regarded as the melting peak, and the peak temperature of the melting peak is defined as the melting point.

(Ion conductivity)
The polymer electrolyte of the present invention preferably has an ionic conductivity of ^10-6 S / cm or more from the viewpoint of ionic conductivity as an electrolyte for battery use and charge / discharge performance of the battery. From the same viewpoint, it is more preferably ^10-5 S / cm or more, and further preferably ^10-4 S / cm or more. The ionic conductivity of the above polymer electrolyte refers to that at 25 ° C.

The ionic conductivity can be measured by the following method. The polymer electrolyte is sampled in a circle with a diameter of 10 mm and used as a measurement sample. After measuring the thickness of this sample with a micrometer, it is placed in a sample holder, and an AC voltage of 100 Hz to 100 MHz is applied using a high-frequency impedance measurement system (4990EDMS-120K manufactured by Toyo Technica), and ions are produced by the complex impedance method. Measure the conductivity. The conductivity of lithium ions in the present invention is preferably ^10-6 S / cm or more, more preferably ^10-5 S / cm or more, from the viewpoint of the internal resistance and rate characteristics of the solid-state battery. ^-4 S / cm or more is most preferable.

(Amplification of raw materials)
The method for atomizing the raw material in the present invention is not limited as long as the effect of the present invention is impaired, and examples thereof include ball mills, jet mills, and cryomills. Further, the raw materials may be atomized and then mixed, but they may be mixed and then atomized. From the viewpoint of mixing uniformity, the average particle size atomized is preferably 20 micrometers or less, and more preferably 10 micrometers or less.

(Thickness of polymer electrolyte)
From the viewpoint of electrical resistance, the thickness of the polymer electrolyte in the present invention is preferably 200 micrometers or less, more preferably 100 micrometers or less, and even more preferably 30 micrometers or less. The thickness of the polymer electrolyte in the present invention is measured with a constant pressure thickness measuring instrument according to JIS K6250 (2019).

(Hygroscopicity)
The hygroscopicity in the present invention refers to the hygroscopic ability of the polymer electrolyte. Specifically, the polymer electrolyte is taken out from a drying chamber having a dew point of −40 ° C. or lower, and treated at 25 ° C. and a relative humidity of 80% for 1 hour. The value obtained by dividing the weight increase before and after the treatment by the weight of the polymer electrolyte before the treatment is defined as the moisture absorption. From the viewpoint of storage of the polymer electrolyte, moisture absorption of the electrolyte may lead to a change in the component ratio and deterioration of the electrolyte. From the above viewpoint, the moisture absorption of the polymer electrolyte in the present invention is preferably 0% or more and 20% or less, and more preferably 0% or more and 10% or less.

(battery)
The battery of the present invention preferably contains the polymer electrolyte of the present invention. It can be produced by a known method without limitation as long as the effect of the present invention is impaired. For example, first, the polymer electrolyte film, the positive electrode material, and the negative electrode material are wound by a winding machine to obtain a wound body. After that, the obtained wound body is sealed with an exterior material to obtain a battery having a polymer electrolyte.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not necessarily limited thereto.

(Measurement of crystallinity)
The crystallinity of the polymer electrolyte referred to here refers to the crystallinity of a film that does not contain an ionizing aid. The crystallinity of the polymer electrolyte in the present invention was measured with a differential scanning calorimeter (DSC). First, the polymer electrolyte was pulverized with a cryomill so that the average particle size was 0.5 mm or less. An aluminum sample holder was filled with 2.5 mg of polymer electrolyte and placed on a sample table. The polymer electrolyte was heated from 25 ° C. to 120 ° C. at a rate of 10 ° C./min under a nitrogen atmosphere and kept at 120 ° C. for 2 hours. After that, the temperature was raised to 400 ° C. at a rate of 10 ° C./min, and among the obtained endothermic peaks, the peak having the widest area was regarded as the melting peak, and the amount of heat of melting (J / g) obtained from the melting peak area was 146. The value divided by 2 (J / g) was taken as the crystallinity (%).

(Measurement of melting point)
The melting point of the polymer electrolyte was measured with a differential scanning calorimetry (DSC). An aluminum sample holder was filled with 2.5 mg of a polymer electrolyte pulverized with a cryomill to an average particle diameter of about 0.5 mm or less, and placed on a sample table. The polymer electrolyte was heated from 25 ° C. to 120 ° C. at a rate of 10 ° C./min under a nitrogen atmosphere and kept at 120 ° C. for 2 hours. After that, the temperature was raised to 400 ° C. at a rate of 10 ° C./min, and among the obtained endothermic peaks, the peak having the widest area was regarded as the melting peak, and the peak temperature of the melting peak was taken as the melting point.

(Measurement of ionic conductivity)
The ionic conductivity in the present invention was measured by the following method. After measuring the thickness of the polymer electrolyte film, sampling was performed so that the diameter was 10 mm, and the area (S) was calculated to be 78.5 mm ² . The polymer electrolyte film was placed in a sample holder (KP-Solid Cell manufactured by Hohsen) having a diameter of 10 mm. After that, using a high frequency impedance measurement system (4990EDMS-120K manufactured by Toyo Technica Co., Ltd.), an AC voltage of 100 Hz to 100 MHz was applied, and the impedance by the complex impedance method was measured. The resistance value (R) was calculated from the obtained impedance, and the ionic conductivity (σ) was calculated by the following formula (3) together with the measured thickness (D) and area (S).

(Measurement of ion diffusion coefficient)
The ion diffusion coefficient of the polymer electrolyte referred to here refers to the ion diffusion coefficient of a film containing an ionizing aid, a polymer and an alkali metal salt. The ion diffusion coefficient in the present invention was measured by PFG-NMR (pulse magnetic field gradient nuclear magnetic resonance spectroscopy). The measurement was carried out at 25 ° C. under a dry nitrogen atmosphere using AVANCE III HD400 manufactured by Bruker Biospin. Observations were made at ⁷ Li and 155.6 MHz. From the diffusion plot, the least squares method was used to fit the two components. Among the obtained values, the largest one was used as the ion diffusion coefficient.

(Measurement of film thickness)
The thickness of the polymer electrolyte film in the present invention was measured with a constant pressure thickness measuring instrument according to JIS K6250 (2019).

(Film containing alkali metal salt)
For the film containing the alkali metal salt in the present invention, the alkali metal salt and the polymer were melt-kneaded and then formed into a film in a film forming step. The film forming method in the present invention may be a known method. The film forming method in the present invention may include a stretching step, but PAS may crystallize due to stretching of the film, which may make it difficult to contain the ionizing aid described later. From the above viewpoint, it is preferable that the film forming method in the present invention does not include a stretching step.

(Ionization aid impregnation)
The impregnation of the ionizing aid in the present invention is carried out by impregnating the film film containing the alkali metal salt and the ionizing aid under certain conditions in a closed container. The impregnation conditions include conditions such as temperature and pressure at the time of impregnation, and were appropriately selected depending on the type of PAS, alkali metal salt and ionizing aid. For example, when a PPS film containing a lithium salt is impregnated with GBL, the film and GBL are placed in a closed container and heated in an oven at 120 ° C. for 1 hour at normal pressure. When the pressure was reduced, the PPS film containing a lithium salt and GBL were placed in an open container and heated at 120 ° C. for 1 hour while being evacuated in a vacuum oven.

(Measurement of moisture absorption)
The hygroscopicity in the present invention refers to the hygroscopic ability of the polymer electrolyte. Specifically, the polymer electrolyte was taken out from a drying chamber having a dew point of −40 ° C. or lower, and treated at 25 ° C. and a relative humidity of 80% for 1 hour. The value obtained by dividing the weight increase before and after the treatment by the weight of the polymer electrolyte before the treatment was taken as the moisture absorption.

(Polymer 1)
For every 100 mol% of all- (Ar-S) -repeating units, Ar is represented by (A) 85 mol% and Ar is represented by (C). A copolymerized polymer consisting of 15 mol% of metaphenylene sulfide constituent units in which both R1 and R2 are hydrogen.

(Polymer 2)
For 100 mol% of all- (Ar-S) -repeating units, 90 mol% of the paraphenylene sulfide constituent unit in which Ar is represented by (A) and Ar is represented by (C), and Ar is represented by (C). A copolymerized polymer consisting of 10 mol% of metaphenylene sulfide constituent units in which both R1 and R2 are hydrogen.

(Polymer 3)
A polymer consisting of only paraphenylene sulfide constituent units in which Ar is represented by (A) with respect to 100 mol% of the repeating unit of-(Ar-S)-(Polyphenylene sulfide "Trelina" (registered trademark) manufactured by Toray Industries, Inc.). E2080).

(Polymer 4)
-(Ar-S)-Repeat unit 100 mol%, Ar is represented by (A) 84 mol%, and Ar is represented by (C), and R1, A copolymerized polymer consisting of 1 mol% of branching units represented by 15 mol% (H) of metaphenylene sulfide constituent units in which both R2 are hydrogen.

(Polymer 5)
A mixture of polymer 1 and polymer 3 in a compositionally converted molar ratio of 1: 1.

(Polymer 6)
Polyethylene (PE).

(Polymer 7)
Polyethylene terephthalate (PET).

(Polymer 8)
Polystyrene (PS).

(Polymer 9)
Polypyrromelitimide (PI) ("Kapton" (registered trademark) manufactured by DuPont Co., Ltd.).

(Alkali metal salt 1)
Lithium bis (trifluoromethanesulfonyl) imide (manufactured by Tokyo Chemical Industry Co., Ltd.).

(Alkali metal salt 2)
Lithium bis (fluorosulfonyl) imide (manufactured by Tokyo Chemical Industry Co., Ltd.).

(Alkali metal salt 3)
Lithium hydroxide (manufactured by Alfa Aesar).

(Example 1)
Polymer 1 was pulverized so that the average particle size was 20 micrometers or less. Then, the pulverized powder was mixed with the alkali metal salt 1. At this time, the mixture was prepared so that the molar ratio of the number of structural units contained in the polymer 1 to the alkali metal salt 1 was 100: 45.4. Specifically, the alkali metal salt 1 was prepared at a ratio of 121 g to 100 g of the polymer 1 powder.

The mixture powder was put into a melt kneader under a dry room condition with a dew point of −40 ° C. and kneaded at 260 ° C. Then, it was cooled to 25 ° C. by air cooling. The obtained sample was again pulverized so that the average particle size was 20 micrometers or less. The obtained powder was formed into a film by a known method and was not stretched. A 30 micrometer film was obtained by the above method. A small amount of the obtained film was sampled, the polymer electrolyte was pulverized with a cryomill until the diameter was 0.5 mm or less, and the crystallinity and melting point were measured.

The obtained film and gamma-butyrolactone (GBL) were placed in a container and impregnated in a vacuum oven at 120 ° C. for 1 hour so that the pressure was adjusted to 0.5 atm. After cooling, the conductive auxiliary agent remaining on the surface was wiped off. The ionic conductivity and hygroscopicity of the obtained polymer electrolyte film were measured at 25 ° C. The measurement results are shown in Table 2. In Example 1, since the melting point of the polymer was low, kneading was possible at a relatively low temperature of 260 ° C., the raw materials did not decompose or deteriorate, and the productivity was excellent. That is, the polymer electrolyte of Example 1 was excellent in good ionic conductivity and productivity at room temperature.

(Examples 2 to 17, Comparative Examples 1 to 5)
Samples were prepared and evaluated in the same manner as in Example 1 except that the polymer type, alkali metal salt type, kneading temperature, stretching ratio, pressure and molar ratio of polymer to alkali metal salt were as shown in Table 1. The evaluation results are shown in Table 2. The mass ratio of each component of the mixed ionizing aid shown in Example 10 was EC (30): PC (30): EMC (40).

Examples 2 to 17 can be molded at a low temperature as in Example 1, and are excellent in productivity and ionic conductivity. That is, the polymer electrolytes of these examples showed good ionic conductivity at room temperature, and were excellent in moldability, productivity, and quality stability, like the polymer electrolytes of Example 1. .. In Example 18, after forming a polymer and an alkali metal salt into a film, biaxial stretching was performed, and the crystallinity was increased by stretching. Due to the increase in crystallinity, the amount of the ionizing aid impregnated decreased, and the ion conductivity was slightly inferior. In addition, Comparative Example 1 does not have a structural unit in which Ar is at least one structure selected from (B) to (G). Therefore, it must be molded at a high temperature. The alkali metal salt deteriorated from the high temperature and was inferior in ionic conductivity. In Comparative Examples 2 to 4, a polymer other than PAS is used, and the affinity with the alkali metal salt and the ionizing aid is lower than that of PAS, so that the ionic conductivity is inferior. In Comparative Example 5, since the ionizing aid is not contained, the dissociation and conduction of the alkali metal salt are insufficient, and the ionic conductivity is inferior.

(Example 18)
Polymer 1 was pulverized so that the average particle size was 20 micrometers or less. Then, the pulverized powder was mixed with the alkali metal salt 1. At this time, the mixture was prepared so that the molar ratio of the number of structural units contained in the polymer 1 to the alkali metal salt 1 was 100: 5.1. Specifically, the alkali metal salt 1 was prepared at a ratio of 13.53 g to 100 g of the polymer 1 powder.

The mixture powder was put into a melt kneading machine under a dry room condition with a dew point of −40 ° C. and kneaded at 260 ° C. The obtained sample was again pulverized so that the average particle size was 20 micrometers or less. The obtained powder was pressed by a press machine heated to 260 ° C., sandwiched between stainless steel plates having a temperature of 15 ° C., and rapidly cooled to obtain a film having a thickness of 30 micrometers. A small amount of the obtained film was sampled, and the crystallinity and melting point were measured.

Then, the obtained film and pure water having an electrical resistivity of 0.5 MΩ (megaohm) were placed in a container and treated in a constant temperature and humidity chamber at 1.0 atm at 60 ° C. for 1 hour to impregnate the pure water. .. The weight of the film before impregnation was measured, the surface of the film was wiped off after the impregnation treatment, and then the weight after impregnation was measured. From the weight changes before and after impregnation, it was found that the alkali metal salt was impregnated at a molar ratio of 1: pure water of 5.1: 71.7.

The ionic conductivity of the obtained polymer electrolyte film was measured at 25 ° C. The measurement results are shown in Table 2.

(Example 19)
A solid electrolyte was obtained in the same manner as in Example 18 except that the impregnation treatment condition in the constant temperature and humidity chamber was 70 ° C. From the weight changes before and after impregnation, it was found that the alkali metal salt was impregnated at a molar ratio of 1: pure water of 5.1: 90.5.

The ionic conductivity of the obtained polymer electrolyte film was measured at 25 ° C. The results are shown in Table 2.

(Example 20)
A solid electrolyte was obtained in the same manner as in Example 18 except that the impregnation treatment condition in the constant temperature and humidity chamber was set to 80 ° C. From the change in weight before and after impregnation, it was found that the mixture was impregnated with a molar ratio of alkali metal salt 1: pure water of 5.1: 136.7.

The ionic conductivity of the obtained polymer electrolyte film was measured at 25 ° C. The results are shown in Table 2.

(Comparative Example 6)
In Comparative Example 6, the polymer was PI (polymer 9), but the melting temperature was 400 ° C. or higher. On the other hand, since the decomposition temperature of the lithium salt (Li salt) is 380 ° C. or lower, vaporization decomposition of the Li salt occurs when the lithium salt is mixed with the Li salt, and the solution cannot be melt-mixed.

(Comparative Example 7)
In Comparative Example 7, LiTFSI and PI (polymer 9) were dissolved in an NMP solution so as to have a molar ratio of 1: 2. Then, a solution of LiTFSI and PI was cast on a PET substrate and dried in a vacuum oven at 120 ° C. for 3 hours. The residual NMP was 4 wt%. The ionic conductivity and hygroscopicity of the obtained electrolyte film were measured. In this comparative example, the initial ionic conductivity at the same level as in the examples was achieved, but due to the high hygroscopicity, electrolysis of water was likely to occur.

(Polymer manufacturing method)
[Reference Example 1]
Add 6.005 kg (25 mol) of sodium sulfide, 0.787 kg (9.6 mol) of sodium acetate and 5 kg of NMP (N-methylpyrrolidone) to an autoclave equipped with a stirrer, and gradually bring it to 205 ° C while passing through nitrogen. The temperature was raised and 3.6 liters of water was distilled off. Next, after cooling the reaction vessel to 180 ° C, 3.712 kg (25.25 mol) of 1,4-dichlorobenzene and 2.4 kg of NMP were added, sealed under nitrogen, heated to 270 ° C, and then at 270 ° C. It reacted for 2.5 hours. Next, it was put into 10 kg of NMP heated to 100 ° C., stirred for about 1 hour, filtered, and further washed with hot water at 80 ° C. for 30 minutes three times. This is filtered, put into 25 liters of an aqueous solution containing 10.4 g of calcium acetate, stirred at 192 ° C. for about 1 hour in a closed autoclave, and then filtered until the pH of the filtrate reaches 7. After washing with ion-exchanged water at about 90 ° C., the mixture was dried under reduced pressure at 80 ° C. for 24 hours to obtain Polymer 3.

[Reference Example 2]
Polymer 1 was obtained by simultaneously adding 3.155 kg (21.46 mol) of 1,4-dichlorobenzene and 0.557 kg (3.79 mol) of 1,3-dichlorobenzene with reference to Reference Example 1. ..

[Reference Example 3]
Polymer 2 is obtained by simultaneously adding 1.341 kg (22.72 mol) of 1,4-dichlorobenzene and 0.371 kg (2.53 mol) of 1,3-dichlorobenzene while referring to Reference Example 1. rice field.

[Reference example 4]
With reference to Reference Example 1, 1,4-dichlorobenzene 3.155 kg (21.46 mol), 1,3-dichlorobenzene 0.557 kg (3.79 mol) and 1,2,4-trichlorobenzene 0. Polymer 4 was obtained by adding 048 kg (0.26 mol) at the same time.

Claims (5)

A polymer electrolyte containing an alkali metal salt, an ionizing aid and a polyarylene sulfide.
The polyarylene sulfide is a polyarylene sulfide copolymer having the formula- (Ar-S)-as a constituent unit.
A polymer electrolyte in which Ar has a structural unit represented by (A) of the chemical formula (1) and at least one structural unit selected from the group consisting of (B) to (G) of the chemical formula (1).

(R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are hydrogen and alkyl groups. It is a substituent selected from an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is selected from an alkylene group, O, CO, SO, and SO _2. ) The ionizing aid has a solvent and
The solvent has a degree of ion dissociation (1-ξ) obtained by the formula (1) at 25 ° C. of 0.1 or more, and a solvent diffusion coefficient obtained by the formula (2) of 15 or less. Item 2. The polymer electrolyte according to Item 1.

The ionizing aid is water, γ-butyrolactone, N-methylpyrrolidone, butylene carbonate (BC), ethylene carbonate (EC) propylene carbonate (PC), methyl-γ-butyrolactone (GVL), triglycrim (TG), diglycyl (DG). ), Ethylmethyl carbonate (EMC), and the polymer electrolyte according to claim 1 or 2, comprising one or more selected from the group consisting of dimethyl carbonate (DMC). The polymer electrolyte according to any one of claims 1 to 3, wherein the alkali metal salt contains at least one of a lithium bis (fluorosulfonyl) imide and a lithium bis (trifluoromethane) sulfonimide. A battery comprising the polymer electrolyte according to any one of claims 1 to 4.