JP2013142095A - Polyglycidol derivative and polyglycidol derivative-containing composition for solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compounds excellent in solubility of ion conductive salts, forming solid electrolytes excellent in ion conductivity, and provide compositions for solid electrolyte containing the compounds.SOLUTION: A polyglycidol derivative is derived from a branched polyglycidol having elements represented by formulas (1) and (2), wherein 10% or more of OH groups of the polyglycidol are blocked by sulfone groups or groups in which the hydrogens of the sulfone groups are substituted with other cations.

Description

  The present invention relates to a compound capable of forming a solid electrolyte having high ionic conductivity, and a composition for a solid electrolyte containing the compound.

  An electrolyte used in a battery such as a secondary battery is a medium that includes an ion conductive salt according to the purpose and has a function of transporting the ion conductive salt between electrodes (ion conductivity). For example, a lithium secondary battery, which is a representative non-aqueous secondary battery, refers to a medium having a function of transporting lithium ions between electrodes.

  Conventionally, in a secondary battery, generally, a solution-based electrolyte (for example, water, ethylene carbonate, propylene carbonate, tetrahydrofuran, etc.) having high ion conductivity has been often used. However, the solution-based electrolyte is highly volatile and easily evaporates or denatures. In addition, since the liquid easily leaks, and it is easy to ignite and burn, it is necessary to use a metal can for the battery exterior and ensure the airtightness of the container. However, the problem is that the shape is limited and the battery mass is heavy.

  Therefore, a secondary battery using a polymer compound as an electrolyte has been developed. The polymer compound is difficult to evaporate and does not leak easily. In addition, a sufficiently high molecular weight polymer compound does not exhibit fluidity at room temperature or higher, so it can be used as a solid electrolyte, and it can serve as a solvent that dissolves ion-conductive salts and solidifies the electrolyte. There is an advantage that it can carry the role to be performed at the same time. Here, the ionic conductivity in the solid electrolyte is expressed by the movement of ions in an amorphous (amorphous) region in the solid electrolyte.

As a polymer compound used for the solid electrolyte, a linear polyether polymer such as polyethylene oxide having a high ability to dissolve an ion conductive salt is known. However, the polyethylene oxide chain is a semi-crystalline polymer, and when a large amount of ionic conductive salt is dissolved, the hydrophilic part of the polyethylene oxide chain forms a complex and crystallizes, so that the ionic conductivity is 10 It was quite low, about ^-6 to 10 ^-7 S / cm.

  As a method for improving the ionic conductivity of a solid electrolyte, it is known to use a branched polyglycidol as a polymer compound contained in the electrolyte (Patent Document 1). When a polymer compound having a branched chain is used, the crystallinity is lowered, and a solid electrolyte having a low density (that is, having a lot of amorphous regions) can be formed even if a large amount of ion conductive salt is dissolved. However, the branched polyglycidol is still not sufficient in terms of the solubility of the ion conductive salt, and a solid electrolyte having further excellent solubility of the ion conductive salt is required.

JP 2000-234020 A

  Accordingly, an object of the present invention is to provide a compound capable of forming a solid electrolyte excellent in solubility of an ion conductive salt and excellent in ion conductivity, and a composition for solid electrolyte containing the compound. .

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that, among the hydroxyl groups in the polyglycidol having a branched chain, a certain percentage of the hydroxyl groups are substituted with sulfone groups or hydrogens of the sulfone groups with other cations. The compound obtained by blocking is a sulfone group or a group obtained by substituting hydrogen of the sulfone group with another cation, so that it has high polarity, so that it has excellent solubility of the ion conductive salt and has a branched chain, so that a large amount of ions Even if the conductive salt is dissolved, the crystallinity is low, a cured material having a low density containing a large amount of amorphous (amorphous) regions can be formed, and a solid electrolyte having high ionic conductivity can be formed. I found it. The present invention has been completed based on these findings.

で示される構成単位を有する分岐鎖状ポリグリシドールから誘導されるポリグリシドール誘導体であって、前記分岐鎖状ポリグリシドールが有するＯＨ基の１０％以上がスルホン基又はスルホン基の水素を他のカチオンで置換した基で封鎖されていることを特徴とするポリグリシドール誘導体を提供する。 That is, the present invention provides the following formulas (1) and (2)

A polyglycidol derivative derived from a branched polyglycidol having a structural unit represented by the formula: wherein 10% or more of the OH groups of the branched polyglycidol have a sulfone group or a hydrogen of the sulfone group as another cation. Provided is a polyglycidol derivative characterized by being blocked with a substituted group.

  The branching degree of the branched polyglycidol is preferably 50% or more.

  The present invention also provides a solid electrolyte composition containing at least the polyglycidol derivative and an ion conductive salt.

  It is preferable that the composition for solid electrolyte further contains a resin component.

  The present invention further provides a solid electrolyte obtained by curing the composition for solid electrolyte. Examples of the shape of the solid electrolyte include a film shape.

  Since the polyglycidol derivative of the present invention has a highly polar substituent, the solubility of the ion conductive salt is excellent. In addition, since the polyglycidol derivative of the present invention has a branched structure, it does not crystallize even when the ion conductive salt is dissolved in a high concentration, has a low density, and has a cured product containing many amorphous (amorphous) regions. The metal ions can smoothly move in the amorphous (amorphous) region. Moreover, the solid electrolyte containing the polyglycidol derivative of the present invention does not volatilize and disappear or denature, has excellent quality retention, does not leak, is flame retardant and has excellent stability.

  Therefore, the secondary battery using the solid electrolyte containing the glycidol derivative of the present invention has extremely high charge and discharge rates. Moreover, since the exterior by a metal can can be omitted and weight reduction is possible, it can contribute to thickness reduction and weight reduction of an electronic device. Therefore, the polyglycidol derivative of the present invention is preferably used for secondary batteries (for example, lithium ion secondary batteries) in portable electronic devices such as mobile phones, PDAs (Personal Digital Assistants), and notebook computers. Can do. Furthermore, in a secondary battery, when a film-like solid electrolyte obtained by curing the composition for solid electrolyte containing the polyglycidol derivative of the present invention into a sheet is used, a separator for separating the positive electrode and the negative electrode is provided. It becomes unnecessary, and the battery constituent members can be further reduced.

[Polyglycidol derivative]
The polyglycidol derivative of the present invention is a polyglycidol derivative derived from a branched polyglycidol having structural units represented by the following formulas (1) and (2), wherein the branched polyglycidol has an OH group 10% or more of these are blocked with a sulfone group or a group obtained by substituting hydrogen of a sulfone group with another cation.

  The branched polyglycidol having the structural units represented by the above formulas (1) and (2) can be synthesized, for example, by polymerizing glycidol or 3-chloro-1,2-propanediol. The average degree of polymerization is, for example, 1 or more, preferably 1 to 50, particularly preferably 2 to 40, most preferably more than 3 and 20 or less. If the average degree of polymerization is below the above range, the crystallinity of the obtained solid electrolyte increases, the amorphous region decreases, and the ionic conductivity tends to decrease. On the other hand, when the average degree of polymerization exceeds the above range, the viscosity tends to be too high and the handling property tends to be lowered.

The polymerization reaction for synthesizing the branched polyglycidol is preferably performed in the presence of a catalyst. Examples of the catalyst include basic catalysts [eg, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; tertiary amines such as triethylamine, piperidine, N-methylpiperidine and pyridine], acid catalysts [ For example, hexafluorophosphoric acid / diethyl etherate (HPF ₆ / OEt ₂ ), phosphoric acid, acetic acid, Lewis acid (for example, trifluoroborate / diethyl etherate (BF ₃ / OEt ₂ ), SnCl ₄ ), etc.] Can be mentioned. Et represents an ethyl group.

  Moreover, it is preferable to perform the said polymerization reaction in presence of the active hydrogen compound used as an initiator. Examples of the active hydrogen compound include monools such as methanol, ethanol, isopropyl alcohol, and benzyl alcohol; polyols such as glycerin, pentaerythritol, sorbitol, diethylene glycol, ethylene glycol, triose, tetraose, pentaose, and hexose; polyvinyl alcohol And polymer compounds having a hydroxyl group such as polyethylene vinyl alcohol.

  As a method for obtaining a glycidol branched polyglycidol having the structural units represented by the above formulas (1) and (2), for example, an active hydrogen compound serving as the initiator and a catalyst are added to a flask, and a predetermined temperature ( For example, after adjusting to 100-120 degreeC, glycidol is dripped and the method of obtaining polyglycidol by making it react (random polymerization and / or block polymerization), stirring, etc. are mentioned.

  The amount of the active hydrogen compound added is, for example, about 0.0001 to 1 mol, preferably 0.001 to 1 mol, particularly preferably 0.005 to 0.5 mol, and most preferably 0 to 1 mol of glycidol. 0.01 to 0.1 mol.

  The amount of the catalyst added is, for example, about 200 to 2000 ppm with respect to the total charged amount.

  The weight average molecular weight (Mw) (in terms of polyethylene glycol) of the branched polyglycidol is, for example, about 200 to 2000, preferably 250 to 1500, and particularly preferably 250 to 1000. Moreover, as molecular weight distribution (Mw / Mn), it is about 1-3, for example, Preferably it is 1-2. If the weight average molecular weight (Mw) of the branched polyglycidol is less than the above range, it tends to be difficult to form a solid electrolyte even if radical polymerization is performed. On the other hand, when the weight average molecular weight (Mw) of the branched polyglycidol exceeds the above range, the viscosity tends to be too high and workability tends to be lowered. The weight average molecular weight of the branched polyglycidol can be determined using, for example, gel filtration chromatography (GPC).

In the present invention, the degree of branching of the branched polyglycidol is represented by the proportion of the structural unit represented by the above formula (1) in the polyglycidol having the structural units represented by the above formulas (1) and (2). And a primary hydroxyl group (hydroxyl group in which one carbon atom is bonded to the carbon atom to which the hydroxyl group is bonded) and secondary hydroxyl group (two carbon atoms to the carbon atom in which the hydroxyl group is bonded) contained in the polyglycidol Can be evaluated by calculating the ratio of primary hydroxyl groups. Specifically, the peak area derived from the carbon atom having a primary hydroxyl group and the carbon atom having a secondary hydroxyl group is measured using ¹³ C-NMR, and can be calculated from the following formula.
Degree of branching (%) = (peak area of carbon atom having primary hydroxyl group / total peak area of carbon atom having primary hydroxyl group and carbon atom having secondary hydroxyl group) × 100

  The degree of branching of the branched polyglycidol of the present invention is, for example, 50% or more, preferably 60% or more, particularly preferably 70% or more, and most preferably 75% or more. A branched polyglycidol having a branching degree within the above range has a low crystallinity and can form a cured product having a low density including many amorphous (amorphous) regions and dissolves a large amount of ion-conducting salt. However, the crystallinity does not increase and a solid electrolyte having extremely high ionic conductivity can be formed.

  As the branched polyglycidol in the present invention, for example, trade name “PGL03P” (triglycerin, branching degree: 71%), trade name “PGL04P” (tetraglycerin, branching degree: 72%), trade name “PGL10PS” Commercial products such as (decaglycerin, branching degree: 78%) (manufactured by Daicel Corporation) can be suitably used.

In the polyglycidol derivative of the present invention, 10% or more (for example, about 10 to 20%, preferably 10 to 18%, particularly preferably 10 to 16%) of the OH group of the branched polyglycidol is a sulfone group (- SO ₃ H) or a hydrogen atom of a sulfone group is blocked with a group substituted with another cation. Among the OH groups of the branched polyglycidol, when the proportion of the groups blocked with the groups is less than the above range, the solubility of a large amount of ion conductive salt tends to decrease, and the ion conductivity tends to decrease. is there. On the other hand, if the ratio blocked with the group becomes too large, the crystallinity of the obtained solid electrolyte increases, the amorphous region decreases, and the ionic conductivity also tends to decrease.

Examples of the group in which the hydrogen of the sulfone group is substituted with another cation include, for example, a hydrogen of a sulfone group such as —SO ₃ Li, —SO ₃ Na, and —SO ₃ K with a metal cation (for example, an alkali metal cation). Examples include substituted groups. The polyglycidol derivative of the present invention may have one kind of group selected from the sulfone group and a group obtained by substituting hydrogen of the sulfone group with another cation, or may have two or more kinds in combination. Good.

In the polyglycidol derivative of the present invention, 10% or more of the OH groups are blocked with a sulfone group (—SO ₃ H) or a group obtained by substituting hydrogen of the sulfone group with another cation, and 10% of the OH groups. Less than (for example, about 3 to 8%) may be blocked with a polymerizable functional group (for example, (meth) acryl group, vinyl group, etc.).

Furthermore, when a polyglycidol derivative having hydrophobicity and / or flame retardancy is desired, for example, 10 to 20% (preferably 10 to 18%, particularly preferably 10 to 16%) of the OH group of the branched polyglycidol. %, Most preferably 10 to 14%) is a halogen atom, an R ₃ Si— group (R: a C 1-6 hydrocarbon group such as methyl, ethyl, butyl group, etc.), a group containing a phosphorus atom (for example, It is preferable to block with H ₂ PO ₄ group or the like.

As a capping method using an OH group sulfone group or a group obtained by substituting hydrogen of the sulfone group with another cation in the branched polyglycidol, a known and commonly used method can be employed. For example, as a method of blocking with lithium sulfonate group (—SO ₃ Li), an aqueous solution of lithium hydroxide is added to branched polyglycidol, and this solution is heated to about 140 ° C. and depressurized to reduce the alkoxide compound. Examples thereof include a method of adding 1,3-propane sultone to the obtained alkoxide compound. The introduction amount of a sulfone group or a group in which hydrogen of the sulfone group is substituted with another cation can be adjusted by controlling the addition amount of 1,3-propane sultone.

  Since the polyglycidol derivative of the present invention has the above-described configuration, the ion-soluble salt is excellent in solubility and has many amorphous regions with low crystallinity even when the ion-conductive salt is added at a high concentration. A cured product having excellent conductivity can be formed.

[Composition for solid electrolyte]
The composition for solid electrolytes of this invention contains the said polyglycidol derivative and an ion conductive salt at least.

As the ionic conductive salt, as long as it is used for usual electrochemical devices can be used without particular limitation, for _{example, LiClO 4, LiBF 4, LiAsF} 6, LiPF 6, LiSbF 6, LiCF ₃ SO ₃ , LiCF ₃ COO, NaClO ₄ , NaBF ₄ , NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg (BF ₄ ) ₂ , (C ₄ H ₉ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NBF ₄ , (C ₄ H ₉ ) ₄ NClO _{4 and the} like can be mentioned. These can be used alone or in combination of two or more.

  The content of the ion conductive salt can be appropriately adjusted depending on the type of the ion conductive salt used, the molecular weight of the polyglycidol derivative, and the like. For example, about 1 to 50 parts by weight with respect to 100 parts by weight of the polyglycidol derivative. The amount is preferably 5 to 30 parts by weight, more preferably 8 to 20 parts by weight. If the content of the ion conductive salt is below the above range, the ion concentration tends to be dilute and the ion conductivity tends to be too low. On the other hand, if the content of the ion conductive salt exceeds the above range, the polyglycidol derivative may exceed the solubility of the ion conductive salt in the ion conductive salt, and the ion conductive salt may be precipitated.

  Moreover, the composition for solid electrolytes of the present invention may contain other components in addition to the polyglycidol derivative and the ion conductive salt. In the present invention, it is particularly preferable to contain a resin component. By containing the resin component, it is possible to impart even better quality retention, liquid leakage prevention and flame retardancy to the solid electrolyte obtained.

  Examples of the resin component include cellulose acetates such as acetyl cellulose, cellulose acetate, cellulose acetate, and cellulose acetate, nitrocellulose, cellulose powder, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, and carboxymethyl. Examples include ethyl cellulose, viscose rayon, vinylon, and cellophane. These can be used alone or in combination of two or more. In the present invention, among them, hydroxyethyl cellulose is used in that it can impart further excellent quality retention, liquid leakage prevention and flame retardancy to the solid electrolyte without causing a decrease in ion conductivity. It is preferable to do.

  The content of the resin component is, for example, about 20 to 60% by weight, preferably 30 to 50% by weight of the total amount of the solid electrolyte composition. If the content of the resin component is less than the above range, the solid electrolyte quality retention, liquid leakage prevention and flame retardancy improving effects tend to be difficult to obtain. On the other hand, when the content of the resin component exceeds the above range, the solubility of the ion conductive salt tends to decrease, and the ion conductivity tends to decrease.

  In addition to the polyglycidol derivative, the solid electrolyte composition of the present invention may further contain a solvent capable of dissolving the ion conductive salt. Examples of the solvent include dibutyl ether, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme, glycol ether. Chain ethers such as ethyl cellosolve, ethyl carbitol, butyl cellosolve, butyl carbitol, etc .; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4,4-dimethyl-1,3-dioxane, etc. A heterocyclic ether of γ-butyrolactone, γ-valerolactone, δ-valerolactone, 3-methyl-1,3-oxazolidine-2-one, 3-ethyl-1,3-oxazolidine-2-one and the like Water, alcohol solvent (eg , Methanol, ethanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, glycerin, etc.), polyoxyalkylene polyols (ethylene oxide, polypropylene oxide, polyoxyethylene / oxypropylene glycol, and two or more of these) ), Amide solvents (for example, N-methylformamide, N, N-dimethylformamide, N-methylacetamide, N-methylpyrrolidinone, etc.), carbonate solvents (for example, propylene carbonate, ethylene carbonate, styrene carbonate, etc.) And imidazolidinone solvents (for example, 1,3-dimethyl-2-imidazolidinone and the like). These can be used alone or in admixture of two or more.

  The solid electrolyte composition of the present invention is prepared by blending the above polyglycidol derivative, an ion conductive salt, and other components as necessary, for example, by stirring and mixing while excluding bubbles under vacuum. The The temperature at the time of stirring and mixing is, for example, about 10 to 60 ° C. For the stirring / mixing, a known apparatus such as a rotation / revolution mixer, a single-screw or multi-screw extruder, a planetary mixer, a kneader, or a dissolver can be used.

[Solid electrolyte]
The solid electrolyte of the present invention is obtained by curing the solid electrolyte composition by drying it at room temperature or in a heating environment. When drying in a heating environment, the heating temperature is, for example, about 100 to 120 ° C.

The solid electrolyte of the present invention has low electrical resistivity and excellent electrical conductivity (that is, excellent ionic conductivity). The electric conductivity [log (σ / Scm ⁻¹ )] of the solid electrolyte of the present invention is, for example, 10 ⁻⁵ or more, preferably 10 ⁻⁴ or more, and particularly preferably 10 ⁻⁴ to 10 ⁻³ .

  In addition, the solid electrolyte of the present invention is excellent in quality retention without being volatilized and lost or modified, hardly leaks, and is flame retardant. Therefore, the secondary battery using the solid electrolyte of the present invention can omit the outer packaging with a metal can and can be reduced in weight. Therefore, it can contribute to the reduction in thickness and weight of electronic devices, and is suitably used for, for example, secondary batteries (for example, lithium ion secondary batteries) in portable electronic devices such as mobile phones, PDAs, and notebook computers. can do.

  Furthermore, the composition for solid electrolyte of the present invention can be molded into a desired shape and cured. For example, a solid electrolyte obtained by molding and curing in the form of a film usually eliminates the need for a separator provided between the positive electrode plate and the negative electrode plate for the purpose of preventing a short circuit due to the contact of the bipolar active material. Enables further weight reduction.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by these Examples.

Synthesis Example 1 [Synthesis of lithium monolithate decaglycerin]
Decaglycerin (branching degree: 78%, trade name “PGL10PS”, manufactured by Daicel Corporation) 166.9 g (0.22 mol), lithium hydroxide monohydrate 9.3 g (0.22 mol) in a four-necked flask Then, the temperature in the reaction system was adjusted to 140 ° C., and the system was depressurized to 20 torr and dried for 8 hours for the purpose of removing moisture. Thereafter, 27.0 g (0.22 mol) of 1,3-propane sultone was added dropwise over 4 hours to obtain monosulfonate lithiated decaglycerin (Compound 1).

Synthesis Example 2 [Synthesis of Lithium Monosulfonate Triglycerin]
Four-neck flask containing 52.8 g (0.22 mol) of triglycerin (branching degree: 71%, trade name “PGL03P”, manufactured by Daicel Corporation) and 9.3 g (0.22 mol) of lithium hydroxide monohydrate Then, the temperature in the reaction system was adjusted to 140 ° C., and the system was depressurized to 20 torr and dried for 8 hours for the purpose of removing moisture. Thereafter, 27.0 g (0.22 mol) of 1,3-propane sultone was added dropwise over 4 hours to obtain monosulfonated triglycerin (compound 2).

Examples 1 and 2
Compounds 1 and 2 obtained in Synthesis Examples 1 and 2 were mixed with an equal amount of water according to the composition of Table 1, developed on a glass substrate, and dried to obtain films 1 and 2.

Comparative Example 1
A film 3 was obtained in the same manner as in Example 1 except that decaglycerin (degree of branching: 25%) was used in place of the compound 1 obtained in Synthesis Example 1.

Comparative Example 2
A film 4 was obtained in the same manner as in Example 1 except that triglycerin (degree of branching: 23%) was used instead of the compound 1 obtained in Synthesis Example 1.

About the films 1-4 obtained by the Example and the comparative example, the ion conductivity was evaluated by the following method.
(Ion conductivity evaluation method)
Conductivity [log (σ / Scm ⁻¹ )] at room temperature (25 ° C.) using a resistivity meter (trade name “Loresta-GP MCP-T610”, manufactured by Mitsubishi Chemical Corporation) equipped with a PSP probe The ion conductivity was evaluated by measuring.

Claims (6)

The following formulas (1) and (2)

A polyglycidol derivative derived from a branched polyglycidol having a structural unit represented by the formula: wherein 10% or more of the OH groups of the branched polyglycidol have a sulfone group or a hydrogen of the sulfone group as another cation. A polyglycidol derivative which is blocked with a substituted group.   The polyglycidol derivative according to claim 1, wherein the degree of branching of the branched polyglycidol is 50% or more.   A composition for a solid electrolyte containing at least the polyglycidol derivative according to claim 1 or 2 and an ion conductive salt.   Furthermore, the composition for solid electrolytes of Claim 3 containing a resin component.   The solid electrolyte obtained by hardening | curing the composition for solid electrolytes of Claim 3 or 4.   The solid electrolyte according to claim 5, which is in the form of a film.