JPH1017708A - Composition capable of forming solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition capable of forming a handleable gel electrolyte, even when containing a large amount of a solvent, compatible with lithium compounds, not depositing a lithium electrolyte dissolved in a solvent, capable of forming a crosslinked structure and capable of forming a soiled electrolyte. SOLUTION: This composition capable of forming a solid electrolyte comprises 100 pts.wt. of an unsaturated cellulose derivative obtained by reacting 1 mole of the residual hydroxyl group of a cellulose ester derivative with 0.01-1 mole of the isocyanate group of an unsaturated monoisocyanate, 10-100 pts.wt. of (meth)acrylonitrile, a lithium compound in an amount of 1-50 pts.wt. per 100 pts.wt. of the total amount of the unsaturated cellulose derivative and the (meth)acrylonitrile, and 10-1000 pts.wt. of a solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition capable of forming a solid electrolyte mainly applicable to a film battery.

[0002]

2. Description of the Related Art Hitherto, attempts have been actively made to obtain a polymer having a polyethylene glycol component as a solid electrolyte. For example, polyethylene glycol itself, or a monomer having a polyethylene glycol component or a urethanized polymer, is polymerized or polyaddition-ized to have a high molecular weight, thereby improving mechanical properties and, on the other hand, reducing conductivity due to crystallization. To obtain a practical polymer.

However, polymers containing polyethylene glycols as one component are essentially water-soluble or hydrophilic, and it is extremely difficult to obtain a non-aqueous water content required for lithium batteries. In addition, the film strength of the obtained polymer must be low as long as it is non-crystalline.

[0004] In addition, the polyethylene glycol component
Since it is poor in tackiness and adhesiveness, a device is required for contact with the electrode.

In addition, a method has recently been proposed in which a solid electrolyte is obtained by impregnating a blend of rubbery polymers with a solvent solution in which a lithium compound is dissolved.

The present inventors have been studying solid electrolytes having good ionic conductivity. However, it is difficult to obtain the desired conductivity simply by using a polymer and a lithium compound together, It has been found that it is difficult to achieve the object unless a so-called gel electrolyte (hereinafter abbreviated as gel electrolyte) in which a solvent serving as an ion carrier is impregnated in a polymer. In this case, it has also been found that, in handling the film, it is essential to increase the strength of the gel as much as possible and to include a large amount of solvent in order to obtain good conductivity. Contradictory properties of both,
In other words, in order to simultaneously increase the strength of the gel while containing a large amount of solvent, it is fundamental that the polymer constituting the gel has a large mechanical strength,
In addition, it was also found that the polymer had a coarse cross-linked structure, that is, it was necessary that the cross-linking interval of the polymer was widened to obtain the required cross-link density, and that the cross-linked portion had sufficient strength. That is, the properties of the polymer required as the gel electrolyte are summarized as follows.

(1) A polymer which forms a gel that can be handled even if it contains a large amount of solvent. (2) It is compatible with the lithium compound and does not precipitate the lithium electrolyte dissolved in the solvent. (3) A crosslinked structure can be formed.

An object of the present invention is to provide a composition capable of forming a solid electrolyte which sufficiently satisfies the properties of a polymer required for the gel electrolyte as described above.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object can be achieved by introducing a step of graft copolymerizing an unsaturated cellulose derivative and a monomer component having a specific composition. Was completed. The polymers used in the present invention all belong to a high polarity group and are not low in polarity like styrene / butadiene copolymer rubber.

That is, according to the present invention, (a) 1 to 1 mole of a residual hydroxyl group of a cellulose ester derivative is used in an amount of from 0.01 to 0.01% of an isocyanate group of an unsaturated monoisocyanate.
Unsaturated cellulose derivative 1 obtained by reacting 1 mole
100 parts by weight, (b) 10 to 1000 parts by weight of a monomer component containing 10 mol% or more of (meth) acrylonitrile, and (c) 100 parts by weight of a total of the unsaturated cellulose derivative and the monomer component for,
1 to 50 parts by weight of a lithium compound, and (d) a total of 1 of the unsaturated cellulose derivative and the monomer component
An object of the present invention is to provide a composition capable of forming a solid electrolyte by mixing 10 to 1000 parts by weight of a solvent capable of dissolving a lithium compound with respect to 00 parts by weight.

The present invention also relates to (a) 100 parts by weight of an unsaturated cellulose derivative and (b) 100 parts by weight of a monomer component.
To 300 parts by weight, and (c) 3 to 20 parts by weight of a lithium compound based on 100 parts by weight of the total of the unsaturated cellulose derivative and the monomer component; and (d) the unsaturated cellulose derivative. An object of the present invention is to provide a composition capable of forming the solid electrolyte, comprising 100 to 800 parts by weight of a solvent capable of dissolving a lithium compound with respect to 100 parts by weight in total of the monomer component.

Further, the present invention provides a composition capable of forming the solid electrolyte, wherein the cellulose derivative is acetyl cellulose.

Further, the present invention provides a composition capable of forming the above-mentioned solid electrolyte in which the cellulose derivative is cellulose acetate butyrate.

The present invention also provides a composition capable of forming the solid electrolyte, wherein the cellulose derivative is cellulose acetate propionate.

The present invention further provides an unsaturated cellulose derivative obtained by reacting 0.1 to 0.5 mol of an isocyanate group of an unsaturated monoisocyanate with 1 mol of a residual hydroxyl group of a cellulose ester derivative. The present invention provides a composition capable of forming the solid electrolyte described above.

Furthermore, the present invention provides a method for producing a lithium compound,
LiClO ₄ , LiBF ₄ , LiPF ₆ and LiCF ₃ S
An object of the present invention is to provide a composition capable of forming at least one of the above solid electrolytes selected from the group consisting of O ₃ .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (Unsaturated Cellulose Derivative) The unsaturated cellulose derivative used in the present invention is obtained by reacting 0.01 to 1 mol of an isocyanate group of an unsaturated monoisocyanate with 1 mol of a residual hydroxyl group of a cellulose ester derivative. It is something that can be done.

The cellulose ester derivative is an esterified product of a glucose hydroxyl group of cellulose, such as acetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like. Currently, commercially available cellulose ester derivatives are intermediate levels of di-substituted to tri-substituted derivatives, and the residual hydroxyl groups are about 8 to 12 mol%. For example, acetyl cellulose is commercially available except for the triacetate type. Cellulose acetate butyrate has a different degree of butylation depending on the use, and 0.8 to 2.4 of three hydroxyl groups per glucose are substituted with butyl groups, and 0.3 to 1.5 are substituted with acetyl groups, Hydroxyl group is 0.2-0.3
About 1.0 to 2.4 of the three hydroxyl groups per glucose in the cellulose acetate propionate and 0.3 to 1.3 in the propionyl group.
0 is replaced by an acetyl group and the hydroxyl group is 0.2
Those having about 0.3 remaining are commercially available.

The unsaturated monoisocyanate for introducing an unsaturated group into a cellulose ester derivative includes the following types.

(A) An unsaturated isocyanate having an isocyanate group and a (meth) acryloyl group in the same molecule. For example, an isocyanate represented by the following formula can be given.

[0021]

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(B) Equivalent reaction product of the isocyanate group of diisocyanate and the hydroxyl group of unsaturated monoalcohol. For example, an isocyanate represented by the following formula can be given.

[0023]

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In this case, the diisocyanate includes two isocyanate groups having different reactivities, for example, 2,4.
-Tolylene diisocyanate, isophorone diisocyanate and the like are preferred.

The use ratio of the cellulose ester derivative and the unsaturated isocyanate is preferably 0.01 to 1 mol, more preferably 0.1 to 0.5 mol, per 1 mol of the hydroxyl group. If the amount is less than 0.01 mol, the formation of the graft polymer tends to be difficult, and the polymerization rate may decrease. In addition, the crosslink density is also reduced, sometimes resulting in a soluble polymer instead of a gel.

The reaction of the cellulose ester derivative and the unsaturated isocyanate is carried out by dissolving both in a type in which both can be dissolved and a lithium compound can be dissolved, and further, there is no reactivity with both active groups. The amount of the solvent used in this case is considered as a part of the "solvent capable of dissolving the lithium compound" described below.

(Monomer component) As the monomer component which is graft-copolymerized with an unsaturated cellulose derivative to form a cross-link, which itself becomes a component of the cross-linked polymer, (meth) acrylonitrile is preferable. Although the reason is not necessarily clear, solvation between the nitrile group and the anion portion of the lithium compound is also conceivable.

The mixing ratio of the monomer component is 10 to 1000 parts by weight per 100 parts by weight of the unsaturated cellulose derivative,
Preferably, the amount is 100 to 300 parts by weight. If the amount is less than 10 parts by weight, the grafting is insufficient, the crosslinked structure of the unsaturated cellulose derivative cannot be formed, and the polymer is dissolved or becomes a weak gel when a solvent is used. Conversely, if it exceeds 1,000 parts by weight, it tends to be difficult to dissolve in a solvent, and it is difficult to form a gel electrolyte which is strong and excellent in handling.

The monomer component may be (meth) acrylonitrile alone, but it is also possible to copolymerize another monomer in order to increase the solubility in a solvent without impairing the conductivity. In this case, the mol% of (meth) acrylonitrile is at least 10 mol% with respect to the monomer component.
It is necessary. Other monomers include, for example, (meth) acrylates.

(Lithium Compound) The lithium compound used in the present invention does not need to be particularly restricted. However, in consideration of conductivity and solubility in a solvent, practically,
For example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃
Lithium compounds such as SO ₃ are exemplified.

The compounding ratio of the lithium compound is 1 to 50 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of the total of the unsaturated cellulose derivative and the monomer component. If the amount is less than 1 part by weight, the conductivity is not sufficiently exhibited. Conversely, if the amount is more than 50 parts by weight, the conductivity does not increase but may decrease.

(Solvent capable of dissolving lithium compound) In the present invention, a solvent capable of dissolving the lithium compound for dissolving the lithium compound and forming a gel electrolyte (hereinafter sometimes simply referred to as a solvent) is required. It is.
The types of solvents that are preferably used are described below.

(I) Carbonates Ethylene carbonate, propylene carbonate, 1-
Butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate; (ii) esters methyl formate, γ-butyrolactone; (iii) ethers tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxolan, dimethoxyethane, diethoxyethane, ethoxymethoxyethane, diethylene glycol, dimethyl ether, diethylene glycol diethyl ether; (iv) nitrogen-containing solvent acetonitrile, dimethylacetamide; and (v) sulfur-containing solvent sulfolane, 3-methylsulfolane, Dimethyl sulfoxide. Of course, these can be used together.

The mixing ratio of these solvents is 10 to 1000 parts by weight, preferably 100 to 800 parts by weight, based on 100 parts by weight of the total of the unsaturated cellulose derivative and the monomer component.
Parts by weight are good. If the amount is less than 10 parts by weight, the conductivity becomes insufficient, and if the amount is more than 1000 parts by weight, the film strength is remarkably weakened and the practicality is impaired.

The preparation of the composition of the present invention can be easily carried out by blending the above-mentioned components in predetermined amounts and mixing them by a known mixing means.

The graft copolymerization of the unsaturated cellulose derivative and the monomer component can be carried out with a lithium compound and a solvent which dissolves the lithium compound or the graft copolymer obtained by graft-copolymerizing the unsaturated cellulose derivative and the monomer component. The product may be immersed in a lithium compound and a solvent that dissolves the lithium compound to form a gel electrolyte.

When a monomer component is polymerized, a radical generator can coexist. In the case of thermal polymerization, when a gel is formed with an organic peroxide, a photoinitiator or light, and then cured by heating. It is preferable to use a combination of a photoreaction initiator and an organic peroxide. As the organic peroxide, a medium-temperature curing type is convenient, but a low-temperature decomposition type can also be used. For example, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, bis (4-t-butylcyclohexyl) par Oxycarbonate, t-butylperoxyoctoate, di-t-butylperoxy-3,3,5
-Trimethylcyclohexane and the like. The photoinitiator is not particularly limited, but a commercially available photoinitiator can be used as it is. For example, dimethylbenzyl ketal, 1-phenyl-2-hydroxy-2-methylpropan-1-one, acylophosphine oxide and the like are generally used. As a light source, not only ultraviolet rays but also energy rays such as visible light and near-infrared light can be used, and combined use with an organic peroxide is also desirable from the viewpoint of photogelation and heat curing.

Further, in putting the composition of the present invention to practical use, it is needless to say that various additives, reinforcing materials, fillers and coloring agents can be used in combination as long as the purpose is not impaired.

In order to shape the obtained composition of the present invention into, for example, a film shape, for example, each component is polymerized in a mold conforming to a desired shape, or the film is gelled by light irradiation, After a desired shape is formed later, heat curing may be performed.

[0040]

The present inventors have conducted intensive studies and found that the graft copolymer of a cellulose ester derivative and (meth) acrylonitrile is a very tough polymer, to which a large amount of a solvent and a lithium compound coexist. The present invention was found to form a gel-like film that can be handled and exhibit ionic conductivity.

[0041]

The present invention will be described below with reference to examples. In the following examples, the solvent capable of dissolving the (meth) acrylonitrile and the lithium compound used was one dehydrated to a water content of 50 ppm or less using a molecular sieve.

Examples 1 to 5 Acetyl cellulose (manufactured by Eastman Chemical Company, trade name CA-394) was placed in a 1-liter separable flask equipped with a stirrer, reflux condenser, thermometer and gas inlet tube.
200 g and 400 g of propylene carbonate (battery grade manufactured by Mitsubishi Chemical Corporation) were heated and dissolved at 30 to 40 ° C., and then isocyanatoethyl methacrylate (trade name MOI, manufactured by Showa Denko KK) as an unsaturated isocyanate.
When 6.5 g and 0.3 g of dibutyltin laurate were added and reacted at 60 to 65 ° C. for 3 hours in dry air, infrared analysis confirmed that the free isocyanate groups had completely disappeared. The calculation indicates that one unsaturated isocyanate group has reacted with 10 molecules of acetylcellulose. Further, 200 g of acrylonitrile was added. This was designated as solution (A). A lithium compound and a solvent were added at the compounding ratios shown in Table 1, and an organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes. Thereafter, the conductivity was measured by an AC impedance method (1 MHz). The results are shown in Table 1.

[0043]

[Table 1]

Examples 6 to 10 Acetyl cellulose (manufactured by Eastman Chemical Company, trade name CA-394) was placed in a 1-liter separable flask equipped with a stirrer, reflux condenser, thermometer and gas inlet tube.
200 g, propylene carbonate (battery grade manufactured by Mitsubishi Chemical Corporation) 400 g, unsaturated isocyanate (2,
Addition reaction product of 1 mol of 4-tolylene diisocyanate and 1 mol of 2-hydroxypropyl methacrylate) 1
1 g and 0.1 g of dibutyltin laurate are added, and 65-70
After reacting at 5 ° C. for 5 hours, infrared analysis confirmed that the free isocyanate groups had completely disappeared. The calculation indicates that one unsaturated isocyanate group has reacted with 10 molecules of acetylcellulose, that is, 10 glucose. To this was added 100 g of acrylonitrile and 100 g of acetoacetoxyethyl methacrylate.
This was designated as solution (B). A lithium compound and a solvent were added at the compounding ratio shown in Table 2, and an organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes.
After polymerization for 2 hours and 80 ° C. for 12 hours, the conductivity was measured by an AC impedance method (1 MHz). The results are shown in Table 2.

[0045]

[Table 2]

Examples 11 to 15 A 1-liter separable flask equipped with a stirrer, reflux condenser, thermometer and gas inlet tube was charged with cellulose acetate propionate (manufactured by Eastman Chemical Co., Ltd.).
200 g of CAP-482-0.5, which has 45% by weight of propionyl groups, 2.5% by weight of acetyl groups and 2.6% by weight of hydroxyl groups), and 200 g of propylene carbonate (battery grade manufactured by Mitsubishi Chemical Corporation). After charging 400 g and dissolving by heating at 30 to 40 ° C., 8.5 g of isocyanate ethyl methacrylate (trade name MOI, manufactured by Showa Denko KK) and 0.3 g of dibutyltin laurate as unsaturated isocyanates were added, and the mixture was dried in dry air. After reacting at ~ 65 ° C for 3 hours, infrared analysis confirmed that the free isocyanate groups had completely disappeared. Calculations show that for about 10 molecules of cellulose acetate propionate,
One unsaturated isocyanate group has reacted.
Further, 200 g of acrylonitrile was added. This was designated as solution (C). A lithium compound and a solvent were added at the compounding ratio shown in Table 3, and an organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes.
After polymerization at 0 ° C. for 12 hours, an AC impedance method (1M
Hz). Table 3 also shows the results.

[0047]

[Table 3]

Examples 16 to 20 Into a 1-liter separable flask equipped with a stirrer, a reflux condenser, a thermometer and a gas inlet tube were placed cellulose acetate propionate (manufactured by Eastman Chemical Co., Ltd.).
200 g of CAP-482-2.0 (trade name, which has 45% by weight of propionyl group, 2.5% by weight of acetyl group, and 1.8% by weight of hydroxyl group) and 200 g of propylene carbonate (battery grade manufactured by Mitsubishi Chemical Corporation). 400 g were charged and dissolved, and 10 g of unsaturated isocyanate (an addition reaction product of 1 mol of 2,4-tolylene diisocyanate and 1 mol of 2-hydroxypropyl methacrylate) and 0.1 g of dibutyltin laurate were added. After reacting at 5 ° C. for 5 hours, infrared analysis confirmed that the free isocyanate groups had completely disappeared. Calculations show that for about 10 molecules of cellulose acetate propionate,
One unsaturated isocyanate group has reacted.
Further, 100 g of acrylonitrile and 100 g of acetoacetoxyethyl methacrylate were added. This was designated as solution (D). A lithium compound and a solvent were added at the compounding ratio shown in Table 4, and an organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes.
After polymerization at 0 ° C. for 12 hours, an AC impedance method (1M
Hz). Table 4 also shows the results.

[0049]

[Table 4]

Examples 21 to 25 In a 1-liter separable flask equipped with a stirrer, a reflux condenser, a thermometer and a gas inlet tube, cellulose acetate butyrate (trade name CAB-381-0. Manufactured by Eastman Chemical Company) was placed. 5, which is 38% by weight of butyryl group, 13.5% by weight of acetyl group, 1.3% of hydroxyl group
% By weight) and 400 g of propylene carbonate (battery grade manufactured by Mitsubishi Chemical Corporation).
After dissolving at ℃ 40 ° C., 10 g of isocyanatoethyl methacrylate (manufactured by Showa Denko KK, trade name MOI) and 0.3 g of dibutyltin laurate are added as unsaturated isocyanates and reacted at 60-65 ° C. in dry air for 3 hours. As a result of infrared analysis, it was confirmed that the free isocyanate group had completely disappeared. Calculations indicate that one isocyanate group has reacted with about 10 molecules of cellulose acetate butyrate. Further acrylonitrile 20
0 g was added. This was designated as solution (E). A lithium compound and a solvent were added at the compounding ratios shown in Table 5, and an organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes. Thereafter, the conductivity was measured by an AC impedance method (1 MHz).
The results are shown in Table 5.

[0051]

[Table 5]

Examples 26 to 30 In a 1-liter separable flask equipped with a stirrer, a reflux condenser, a thermometer, and a gas inlet tube, cellulose acetate butyrate (trade name CAB-551-0, manufactured by Eastman Chemical Company) was placed. 2. This was charged with 200 g of butyryl group 52% by weight, acetyl group 2.0% by weight, and hydroxyl group 1.8% by weight) and 400 g of propylene carbonate (Mitsubishi Chemical Corporation battery grade), and dissolved and dissolved. 9 g of isocyanate (an addition reaction product of 1 mol of 2,4-tolylene diisocyanate and 1 mol of 2-hydroxypropyl methacrylate) and 0.1 g of dibutyltin laurate are added, and when reacted at 65 to 70 ° C. for 5 hours, a red color is obtained. As a result of external analysis, it was confirmed that the free isocyanate group had completely disappeared. Calculations indicate that one isocyanate group has reacted with about 10 molecules of cellulose acetate butyrate. Further, 100 g of acrylonitrile and 100 g of acetoacetoxyethyl methacrylate were added. This was designated as solution (F). Table 6
A lithium compound and a solvent are added in the proportions shown in
An organic peroxide was added, and the mixture was cast at intervals of 0.5 mm between platinum electrodes. After polymerization in a nitrogen stream at 60 ° C. for 2 hours and 80 ° C. for 12 hours, conductivity was measured by an alternating current impedance method (1 MHz). Table 6 also shows the results.

[0053]

[Table 6]

[0054]

According to the present invention, (1) a gel electrolyte which can be handled even if it contains a large amount of a solvent can be obtained; (2) it is compatible with a lithium compound and does not precipitate a lithium electrolyte dissolved in the solvent; (3) A crosslinked structure can be formed; a composition capable of forming a solid electrolyte is provided.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08G 18/81 NFN C08G 18/81 NFN C08L 33/20 LJJ C08L 33/20 LJJ

Claims (7)

[Claims] (1) 100 parts by weight of an unsaturated cellulose derivative obtained by reacting 0.01 to 1 mole of an isocyanate group of an unsaturated monoisocyanate with 1 mole of a residual hydroxyl group of a cellulose ester derivative. On the other hand, (b) 10 to 1000 parts by weight of a monomer component containing 10 mol% or more of (meth) acrylonitrile is blended, and (c) lithium is added to 100 parts by weight of the total of the unsaturated cellulose derivative and the monomer component. Compound 1
And (d) a solid electrolyte formed by mixing 10 to 1000 parts by weight of a solvent capable of dissolving a lithium compound with respect to 100 parts by weight of the total of the unsaturated cellulose derivative and the monomer component. Possible composition. 2. 100 parts by weight of the unsaturated cellulose derivative (a), 100 to 300 parts by weight of the monomer component (b), and (c) a total of 100 parts by weight of the unsaturated cellulose derivative and the monomer component. 3 to 20 parts by weight of a lithium compound, and (d) a total of 100 parts by weight of the unsaturated cellulose derivative and the monomer component
1 part by weight of a solvent capable of dissolving a lithium compound
The composition capable of forming the solid electrolyte according to claim 1, wherein the composition comprises from 0.00 to 800 parts by weight. 3. The composition according to claim 1, wherein the cellulose derivative is acetylcellulose. 4. The composition capable of forming a solid electrolyte according to claim 1, wherein the cellulose derivative is cellulose acetate butyrate. 5. The composition according to claim 1, wherein the cellulose derivative is cellulose acetate propionate. 6. An unsaturated cellulose derivative obtained by reacting 0.1 to 0.5 mol of an isocyanate group of an unsaturated monoisocyanate with 1 mol of a residual hydroxyl group of a cellulose ester derivative. Item 6. A composition capable of forming the solid electrolyte according to any one of Items 1 to 5. 7. The method according to claim 1, wherein the lithium compound is LiClO ₄ , Li
BF _4, LiPF ₆ and LiCF ₃ SO claims 1 to at least one selected from the group consisting of ₃ to the solid electrolyte forming composition according to any one of 6.