JP6401586B2 - Aliphatic polycarbonate resin, solid electrolyte, and lithium ion secondary battery - Google Patents

Description

  The present invention relates to an aliphatic polycarbonate resin, a solid electrolyte, and a lithium ion secondary battery.

Unlike a liquid electrolyte, a solid electrolyte is a lightweight and flexible electrolyte that does not have to worry about liquid leakage. Therefore, it is expected to be applied to a secondary battery using lithium ions or the like. As a representative solid electrolyte, many polyether electrolytes such as polyethylene oxide (PEO) have been studied. For example, Non-Patent Document 1 describes a polyethylene glycol obtained by polymerizing cyanoepoxide.
In recent years, research on polycarbonate-based electrolytes has been promoted. For example, Patent Document 1 describes an organic polymer and metal salt having a polyalkylene carbonate unit in the main chain, and a polymer solid electrolyte containing an organic solvent compatible with these organic polymer and metal salt. ing. Patent Document 2 describes a polymer solid electrolyte containing a polycarbonate, which is a copolymer of epoxide and carbon dioxide, and a metal salt. Patent Document 3 describes a solid polymer electrolyte containing an aliphatic polycarbonate having a side chain having a structure in which a substituent is bonded via an ether bond, and an electrolyte salt compound.

Japanese Patent No. 3384174 JP 2013-155213 A JP 2010-287563 A

Journal of Macromolecular Science, Chemistry 7 1484-1508 (1973).

  However, practical ion conductivity has not been obtained, and a new polymer design is required.

  An object of the present invention is to provide an aliphatic polycarbonate resin, a solid electrolyte, and a lithium ion secondary battery capable of obtaining a practical level of ionic conductivity.

  The aliphatic polycarbonate resin which concerns on 1 aspect of this invention contains the structural unit which has group represented by following General formula (1).

(In the general formula (1), R ₁ is an electron-withdrawing group, L is 1 or 2, and m is 0 or a positive integer.)

  In the aliphatic polycarbonate resin according to one embodiment of the present invention, the structural unit having a group represented by the general formula (1) preferably includes a structural unit represented by the following general formula (2).

(In the general formula (2), R ₁ , L, and m are the same as described above, n is a positive integer, and R ₂ is a hydrogen atom or an alkyl group.)

In the aliphatic polycarbonate resin according to one embodiment of the present invention, the alkyl group as R ₂ is preferably an alkyl group having 1 to 3 carbon atoms.

In the aliphatic polycarbonate resin according to one embodiment of the present invention, R ₂ is preferably a hydrogen atom or a methyl group.

  In the aliphatic polycarbonate resin according to one embodiment of the present invention, m is preferably an integer of 0 or more and 5 or less.

In the aliphatic polycarbonate resin according to an aspect of the present invention, R ₁ is preferably a group selected from the group consisting of a cyano group, a cyclic ether group, and a cyclic carbonate group.

In the aliphatic polycarbonate resin according to one embodiment of the present invention, R ₁ is a cyano group, a 1,3-dioxolan-2-one-4-yl group, a 2-tetrahydrofuranyl group, or a 3-tetrahydrofuranyl group. It is preferable.

In the aliphatic polycarbonate resin according to one embodiment of the present invention, R ₁ is preferably a cyano group.

  The solid electrolyte according to one embodiment of the present invention preferably includes the aliphatic polycarbonate resin according to one embodiment of the present invention and a metal salt.

  In the solid electrolyte according to one embodiment of the present invention, the metal salt is preferably a lithium salt.

  In the solid electrolyte according to one embodiment of the present invention, the lithium salt preferably includes at least one of lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide.

  In the solid electrolyte according to one embodiment of the present invention, the molar ratio of metal to all carbonate groups (metal / total carbonate groups) in the aliphatic polycarbonate resin is preferably 0.05 or more and 4 or less.

  The lithium ion secondary battery according to one embodiment of the present invention preferably includes the solid electrolyte according to one embodiment of the present invention described above.

  According to one embodiment of the present invention described above, it is possible to provide an aliphatic polycarbonate resin, a solid electrolyte, and a lithium ion secondary battery that can obtain a practical level of ionic conductivity.

It is a ^{1 H-NMR} spectrum of the epoxide monomer synthesized in Example. Is a ^{1 H-NMR} spectrum of the aliphatic polycarbonate resins A synthesized in Example. It is an Arrhenius plot which shows the relationship between the reciprocal of temperature, and the common logarithm of ion conductivity.

  The present invention will be described by taking one embodiment as an example.

[Aliphatic polycarbonate resin]
The aliphatic polycarbonate resin according to the present embodiment includes a structural unit having a group represented by the following general formula (1). By introducing a group represented by the following general formula (1) into the side chain of the aliphatic polycarbonate resin, the ionic conductivity can be improved.

In the general formula (1), R ₁ is an electron-withdrawing group, L is 1 or 2, and m is 0 or a positive integer.
In the present embodiment, m is preferably an integer of 0 or more and 5 or less. If m is 5 or less, the polymerization of the monomer is easy to proceed. Furthermore, since the ether chain takes a solvated structure with the cation, the shorter the ether chain, the better the ionic conduction.
In the present embodiment, m is more preferably an integer of 0 or more and 3 or less, and further preferably 1 or 2.

In the present embodiment, the “electron withdrawing group” is a substituent having an effect of promoting dissociation of the salt.
In the present embodiment, examples of the electron-withdrawing group as R ₁ include a cyano group, a cyclic ether group, a cyclic carbonate group, a halogen atom, and a sulfonyl group. When there are a plurality of structural units having a group represented by the general formula (1), the plurality of R ₁ may be the same as or different from each other.

In the present embodiment, R ₁ is preferably a group selected from the group consisting of a cyano group, a cyclic ether group, and a cyclic carbonate group. Examples of the cyclic ether group include a 2-tetrahydrofuranyl group, a 3-tetrahydrofuranyl group, a 2-tetrahydropyranyl group, a 3-tetrahydropyranyl group, a 4-tetrahydropyranyl group, a 2-oxepanyl group, and a 3-oxepanyl group. And 4-oxepanyl group. Examples of the cyclic carbonate group include a 1,3-dioxetan-2-one-4-yl group, a 1,3-dioxolan-2-one-4-yl group, and a 1,3-dioxan-2-one-4-yl group. Yl group, 1,3-dioxan-2-one-5-yl group, 1,3-dioxepan-2-one-4-yl group, 1,3-dioxepan-2-one-5-yl group and the like Can be mentioned.

In this embodiment, when R ₁ is a cyano group, L is preferably 2. When R ₁ is a group selected from the group consisting of a cyclic ether group and a cyclic carbonate group, L is 1. Is preferred.

In the present embodiment, R ₁ is more preferably a cyano group, a 2-tetrahydrofuranyl group, a 3-tetrahydrofuranyl group, or a 1,3-dioxolan-2-one-4-yl group, and has an ionic conductivity. From the viewpoint of further improvement, a cyano group is more preferable.

The aliphatic polycarbonate resin according to this embodiment preferably contains an alkylene carbonate as a structural unit having a group represented by the general formula (1). The alkylene carbonate preferably has a structure in which a methylene chain represented by the general formula — (CH ₂ ) _x — is bonded to the carbonate group. x is preferably an integer of 1 or more, more preferably an integer of 2 or more and 10 or less, and further preferably an integer of 2 or more and 6 or less. Specifically, examples of the alkylene carbonate include methylene carbonate, ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, pentamethylene carbonate, and hexamethylene carbonate. The group represented by the general formula (1) as a side chain is preferably bonded to a carbon atom in place of any hydrogen atom in the methylene chain. The aforementioned methylene chain may have a substituent, and examples of the substituent include an alkyl group.

  From the viewpoint of ease of synthesis and improvement of ionic conductivity, the aliphatic polycarbonate resin according to this embodiment preferably contains ethylene carbonate, and includes a structural unit represented by the following general formula (2) as ethylene carbonate. It is more preferable. That is, the aliphatic polycarbonate resin according to the present embodiment preferably includes a structural unit represented by the following general formula (2).

In the general formula (2), R ₁ , L, and m are the same as described above, n is a positive integer, and R ₂ is a hydrogen atom or an alkyl group.
In the present embodiment, the alkyl group as R ₂ is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an alkyl group having 1 or 2 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group and an ethyl group.
R ₂ is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

  The molecular weight of the aliphatic polycarbonate resin according to the present embodiment is 5,000 to 5,000,000 in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method when expressed in terms of weight average molecular weight (Mw). The range is preferable, and the range of 10,000 to 1,000,000 is more preferable.

(Method for producing aliphatic polycarbonate resin)
The manufacturing method of the aliphatic polycarbonate resin according to the present embodiment is not particularly limited. The aliphatic polycarbonate resin of the present embodiment includes, for example, an epoxide monomer having a group represented by the general formula (1) in the presence of a polymerization catalyst (described by the following general formula (3), as described in Examples below. ) And carbon dioxide can be copolymerized.

(In the general formula (3), R ₁ , R ₂ , L, and m are the same as described above.)

Note that R ₂ is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom, because it has high reactivity and the epoxide is easy to open during polymerization.

  It does not specifically limit as a polymerization catalyst used when manufacturing the aliphatic polycarbonate resin which concerns on this embodiment, An organic zinc type catalyst, a metal salen complex catalyst (for example, cobalt salen complex catalyst etc.), etc. can be illustrated.

The amount of the polymerization catalyst used for the copolymerization reaction of the epoxide monomer and carbon dioxide is preferably 0.2 mol or less with respect to 1 mol of the epoxide monomer in the case of an organozinc catalyst, for example. Preferably it is 0.1 mol or less, More preferably, it is 0.05 mol or less. In addition, for example, in the case of a metal salen complex catalyst, it is preferably 0.05 mol or less, more preferably 0.01 mol or less, further preferably 0.001 mol or less with respect to 1 mol of the epoxide monomer. .
Further, when a metal salen complex catalyst is used, a cocatalyst can be used. As the promoter, for example, an onium salt compound is preferable. Specific examples of the onium salt compound include, but are not limited to, bis (triphenylphosphoranylidene) ammonium chloride (PPNCl), piperidine, bis (triphenylphosphoranylidene) ammonium fluoride from the viewpoint of high reaction activity. (PPNF), ammonium pentafluorobenzoate (PPNOBzF ₅ ), tetra-n-butylammonium chloride (nBu ₄ NCl) and the like are preferable.

The optimum polymerization conditions such as pressure vary depending on the type of catalyst. For example, the pressure of carbon dioxide in the reaction vessel is 0.1 MPa or more and 10 MPa or less, preferably 0.5 MPa or more and 7.0 MPa or less. It is.
The polymerization temperature is, for example, 40 ° C. or more and 100 ° C. or less, preferably 60 ° C. or more and 80 ° C. or less in the case of an organozinc catalyst. Further, for example, in the case of a cobalt-salen complex catalyst, the catalytic action works well and the reaction rate is accelerated, so that the room temperature (25 ° C.) is preferable.

In the method of copolymerizing the epoxide monomer and carbon dioxide, examples of the epoxide monomer used as a starting material include ethylene oxide and propylene oxide.
In addition, although the epoxide monomer which has group represented by the said General formula (1) is compoundable by the method described in the nonpatent literature 1, for example, the synthesis method is the synthesis | combination described in the nonpatent literature 1. The method is not limited.

  In addition to polymerizing the epoxide monomer having the group represented by the general formula (1), the aliphatic polycarbonate resin in this embodiment may be subjected to a polymerization reaction in the presence of a monomer having another structure. Examples of the monomer to be copolymerized include monomers having a group having an unsaturated double bond such as an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. Specifically, for example, methyl acrylate, ethyl acrylate, butyl acrylate, acrylamide, methyl methacrylate, methacrylamide, butadiene, acrylonitrile, styrene, vinyl acetate, vinyl chloride, 2-ethoxyethyl acrylate, 2- (2 -Ethoxyethoxy) ethyl acrylate, diethylene glycol ethyl ether acrylate, polyethylene glycol alkyl ether acrylate, polypropylene glycol alkyl ether acrylate, and compounds such as 2-cyanoethyl acrylate.

  From the viewpoint of ion conductivity, the aliphatic polycarbonate resin according to the present embodiment preferably contains the repeating unit represented by the general formula (2) in an amount of 50 mol% or more, and 80 mol% or more in all repeating units. More preferably.

[Solid electrolyte]
The solid electrolyte according to the present embodiment includes the aliphatic polycarbonate resin according to the present embodiment and a metal salt.
The content of the aliphatic polycarbonate resin in the solid electrolyte is preferably 5% by mass to 99% by mass (of the solid electrolyte), and more preferably 10% by mass to 95% by mass.

  In the solid electrolyte according to the present embodiment, the metal salt is preferably at least one of alkali metal salts. Examples of the alkali metal salt include lithium salt, sodium salt, potassium salt and the like.

In the present embodiment, the metal salt is preferably a lithium salt. In the solid electrolyte, the metal salt can exist as a cation such as an alkali metal and a counter ion of the cation. If the metal salt is a lithium salt, the energy density is higher.
Examples of the lithium _{salt, LiClO 4, LiBF 4, LiI} , LiPF 6, LiCF 3 SO 3, LiCF 3 COO, LiNO 3, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) ₄ , LiCH ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) N, Li (FSO ₂ ) ₂ N, and Li [(CO ₂ ) ₂ ] ₂ B and the like. Among these, from the viewpoint of ion conductivity, Li (CF ₃ SO ₂ ) ₂ N (lithium bis (trifluoromethanesulfonyl) imide: LiTFSI) and Li (FSO ₂ ) ₂ N (lithium bis (fluorosulfonyl) imide: LiFSI It is more preferable to include at least one of the above. Multiple types of metal salts may be included in the solid electrolyte.

  In the solid electrolyte according to the present embodiment, a metal (which is a metal derived from a metal salt) with respect to all carbonate groups (—O—CO—O—) in the aliphatic polycarbonate resin according to the present embodiment, and dissociates from the metal salt. The molar ratio (metal / total carbonate group) is preferably 0.05 or more and 4 or less, preferably 0.1 or more and 3 or less. Or less, more preferably 0.1 or more and 2 or less.

  The solid electrolyte according to the present embodiment may contain components other than the aliphatic polycarbonate resin and the metal salt according to the present embodiment as long as the object of the present invention is not impaired.

  For example, the solid electrolyte according to the present embodiment may be a solid (solvent-free solid electrolyte) that does not include a solvent, or may be a gel (polymer gel electrolyte) that includes a solvent. When the solid electrolyte is a polymer gel electrolyte, the content of the solvent in the polymer gel electrolyte is usually 30% by mass or more and 99% by mass or less of the entire solid electrolyte.

  The method for producing the solid electrolyte according to the present embodiment is not particularly limited. For example, the monomer may be polymerized to obtain an aliphatic polycarbonate resin, and then the metal salt may be contained, or the monomer in the presence of the metal salt. May be polymerized to form an aliphatic polycarbonate resin. In the case of the former method, for example, a solid electrolyte can be obtained by adding a metal salt and a solvent to the aliphatic polycarbonate resin according to the present embodiment and dissolving it, and then removing the solvent.

The form and configuration of the solid electrolyte according to the present embodiment are not particularly limited. For example, a membrane-like solid electrolyte membrane may be used. The solid electrolyte membrane is preferably self-supporting. A solid electrolyte membrane having self-supporting properties is excellent in handling. The self-supporting membrane is a membrane that can be handled by being able to peel off the solid electrolyte membrane while maintaining its shape from the support.
The solid electrolyte membrane can be manufactured as follows. For example, aliphatic polycarbonate resin according to the present implementation embodiment, a metal salt, and a mixed solution containing a solvent is applied to the surface of the support to form a coating film, by removing the solvent in the coating film, film-like The solid electrolyte membrane can be obtained. At this time, when it is necessary to peel the solid electrolyte membrane from the support, it is preferable that the surface of the support is subjected to a peeling treatment.

In the aliphatic polycarbonate resin according to the present embodiment, the main chain includes a carbonate group (—O—CO—O—), and the side chain bonded to the main chain includes an electron withdrawing group. Therefore, the dissociation property of the salt and the flexibility of the polymer increase, and it is difficult to crystallize even if a large amount of the metal salt is dissolved. Therefore, the solid electrolyte containing the aliphatic polycarbonate resin according to the present embodiment can increase the carrier density by dissolving a large amount of the metal salt. Therefore, according to the aliphatic polycarbonate resin which concerns on this embodiment, ionic conductivity can be improved. The conventional polyethylene oxide polymer and the conventional aliphatic polycarbonate resin have a smaller amount of the metal salt that can be dissolved than the aliphatic polycarbonate resin according to the present embodiment. When the amount is increased, the glass transition temperature of the polymer increases, so that the ion mobility decreases and the ionic conductivity decreases. Further, the crystallization of the salt causes a decrease in membrane strength and ionic conductivity.
Moreover, since the aliphatic polycarbonate resin which concerns on this embodiment is a structure which contains a carbonate group in a principal chain, superposition | polymerization is easy and molecular weight can also be enlarged. Therefore, by using the aliphatic polycarbonate resin according to the present embodiment, a solid electrolyte membrane having self-supporting properties can be obtained.
Furthermore, since the aliphatic polycarbonate resin according to the present embodiment has an electron-withdrawing group in the side chain, it does not form a strong complex structure with the dissolved metal ions, and has an appropriate interaction. Can be maintained. Therefore, even if the metal salt is at a low concentration, the ionic conductivity is good.

  Since the solid electrolyte according to the present embodiment is excellent in ion conductivity, it can be suitably used for, for example, a battery. As a battery containing the solid electrolyte which concerns on this embodiment, a lithium ion battery, a lithium secondary battery, etc. can be mentioned, for example.

[Lithium ion secondary battery]
The lithium ion secondary battery according to the present embodiment preferably includes the solid electrolyte according to the present embodiment. In the present embodiment, the solid electrolyte according to the present embodiment is preferably included as a constituent material of the electrolyte layer of the lithium ion secondary battery. The lithium ion secondary battery includes an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode. By setting it as the said structure, the lithium ion secondary battery excellent in the characteristic can be obtained.
The solid electrolyte membrane may be directly formed on the electrode by applying a mixed solution containing the aliphatic polycarbonate resin, the metal salt, and the solvent to the electrode and removing the solvent. Various members included in the lithium ion secondary battery according to the present embodiment are not particularly limited, and for example, materials generally used for batteries can be used.
And even if the solid electrolyte which concerns on this embodiment does not contain a solvent, it has ion conductivity. Therefore, if the lithium ion secondary battery according to the present embodiment is a battery that includes the solid electrolyte according to the present embodiment and does not include a solvent, the battery can be used safely without leakage.

  In addition, this invention is not limited to the said embodiment, The deformation | transformation in the range which can achieve the objective of this invention, improvement, etc. are contained in this invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

[NMR measurement]
The structures of various aliphatic polycarbonates used in the examples were confirmed using nuclear magnetic resonance spectroscopy ( ¹ H-NMR, JEOL EX-400 manufactured by JEOL Ltd.). As the solvent, d-chloroform (not containing TMS) was used.

<Example 1>
[Synthesis of aliphatic polycarbonate resin]
(Monomer synthesis)
First, cyanoethyl glycidyl ether (the following formula) as a monomer was synthesized according to the method described in Non-Patent Document 1. The structure of the obtained epoxide monomer was confirmed by ¹ H-NMR (FIG. 1).

(Synthesis of polymerization catalyst)
According to the following operation, zinc glutarate (ZnGA) was prepared as a zinc-based catalyst.
Zinc oxide (ZnO: manufactured by Kanto Chemical Co., Inc.) and glutaric acid (GA: manufactured by Kanto Chemical Co., Ltd.) were weighed so as to have a molar ratio of 1: 0.99. These reagents were stirred with 90 mL of toluene at 55 ° C. for 4 hours in a 200 mL eggplant flask equipped with a Dean-Stark tube, and then refluxed at around 140 ° C. for 24 hours. Since water is generated as a by-product during the reflux, the water generated by the reaction was recovered using a Dean-Stark tube.
After completion of the reaction, the reaction product was washed several times with acetone, and then the washed reaction product was collected by filtration. Subsequently, the reaction product collected by filtration was placed in a desiccator, dried under reduced pressure using a diaphragm pump, dried under reduced pressure, and further vacuum dried at 80 ° C. Thereafter, the reaction product was finely crushed using a spatula and further vacuum dried at 120 ° C. to obtain white powder-like ZnGA.

(polymerization)
Next, the aliphatic polycarbonate resin A according to this example was synthesized.
The synthesized epoxide monomer and the synthesized ZnGA (polymerization catalyst) were weighed to a molar ratio of 20: 1 and stirred in a pressure vessel. All these operations were performed in a glove box under an argon atmosphere. Subsequently, the pressure in the flask was purged with CO _2, the CO ₂ is introduced into the pressure vessel by the liquid feed pump, the pressure in the pressure vessel to 6.4 MPa, 48 hours at 60 ° C., a polymerization reaction was carried out . The synthesis scheme of epoxide monomer and carbon dioxide is shown below.

After completion of the reaction, chloroform was added to the contents of the pressure vessel to prepare a chloroform solution, which was suction filtered to remove ZnGA. Next, the filtrate was concentrated using a rotary evaporator, and then the filtrate after concentration was dropped into stirring methanol to precipitate the product.
Thereafter, the product was dried under reduced pressure using a diaphragm pump in a desiccator, and then vacuum dried at 60 ° C. to obtain an aliphatic polycarbonate resin A having a weight average molecular weight of 21,000. The structure of the obtained aliphatic polycarbonate resin A was confirmed by ¹ H-NMR (FIG. 2).

Next, an electrolyte membrane made of a solid electrolyte according to this example was manufactured.
LiTFSI weighed so that the molar ratio [Li] / [— O—CO—O—] of lithium to all carbonate groups is 0.2 is mixed with the aliphatic polycarbonate resin A obtained by the above polymerization. The solid electrolyte was obtained by stirring well. Thereafter, the solid electrolyte is cast on a fluororesin mold, dried at 60 ° C. for 6 hours in a dry nitrogen atmosphere, and further dried at 60 ° C. for 24 hours under reduced pressure. [Li] / [— O—CO—O An electrolyte membrane having a molar ratio of-] of 0.2 was obtained.

<Example 2>
The same as Example 1 except that LiTFSI weighed so that the molar ratio [Li] / [— O—CO—O—] of lithium to the total carbonate groups was 0.6 was mixed with the aliphatic polycarbonate resin A. In the procedure, an electrolyte membrane having a molar ratio of [Li] / [— O—CO—O—] of 0.6 was obtained.

<Example 3>
The same as Example 1 except that LiTFSI weighed so that the molar ratio [Li] / [-O-CO-O-] of lithium to the total carbonate groups was 0.8 was mixed with the aliphatic polycarbonate resin A. In the procedure, an electrolyte membrane having a molar ratio of [Li] / [— O—CO—O—] of 0.8 was obtained.

<Example 4>
The same as Example 1 except that LiTFSI weighed so that the molar ratio [Li] / [— O—CO—O—] of lithium to the total carbonate groups was 3.76 was mixed with the aliphatic polycarbonate resin A. In the procedure, an electrolyte membrane having a [Li] / [— O—CO—O—] molar ratio of 3.76 was obtained.

<Comparative Example 1>
[Li] / [— O—CO—O—] in the same procedure as in Example 1 except that “QPAC-25” (trade name) manufactured by EMPOWER MATERIALS was used instead of the aliphatic polycarbonate resin A. An electrolyte membrane having a molar ratio of 0.2 was obtained. QPAC is a registered trademark.

<Comparative Example 2>
Instead of the aliphatic polycarbonate resin A, “QPAC-25” (trade name) manufactured by EMPOWER MATERIALS was used, and the molar ratio [Li] / [— O—CO—O—] of lithium to all carbonate groups was 0.6. An electrolyte membrane having a [Li] / [— O—CO—O—] molar ratio of 0.6 was obtained in the same procedure as in Example 1 except that LiTFSI weighed so as to be mixed was obtained.

<Comparative Example 3>
Instead of the aliphatic polycarbonate resin A, “QPAC-25” (trade name) manufactured by EMPOWER MATERIALS was used, and the molar ratio [Li] / [— O—CO—O—] of lithium to all carbonate groups was 0.8. An electrolyte membrane having a [Li] / [— O—CO—O—] molar ratio of 0.8 was obtained in the same procedure as in Example 1 except that LiTFSI weighed so as to be mixed was obtained.

<Comparative example 4>
Instead of aliphatic polycarbonate resin A, “QPAC-25” (trade name) manufactured by EMPOWER MATERIALS was used, and the molar ratio of lithium to the total carbonate group [Li] / [— O—CO—O—] was 3.76. An attempt was made to produce an electrolyte membrane having a [Li] / [— O—CO—O—] molar ratio of 3.76 in the same manner as in Example 1 except that LiTFSI weighed so as to be mixed was mixed. However, the salt was deposited and the electrolyte membrane could not be obtained.

[Performance evaluation of electrolyte membrane]
(Ionic conductivity)
The electrolyte membranes obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were each cut into a circle having a diameter of 16 mm, sandwiched between two stainless plates as electrodes, and the impedance between the stainless plates was measured at 40 ° C. and 50 ° C. Measured at 0 ° C, 60 ° C, 70 ° C, and 80 ° C. For the measurement, an alternating current impedance method was used in which an alternating current (applied voltage: 10 mV) was applied between the electrodes to measure a resistance component. Ionic conductivity was calculated from the real impedance intercept of the obtained Cole-Cole plot. For the measurement, potentiostat / galvanostat (product name: SP-150, manufactured by biologic) was used.
The ionic conductivity (σ) was determined by the following formula (1).
σ = L / (R × S) (1)
In the formula (1), σ is ionic conductivity (unit is S / cm), R is resistance (unit is Ω), S is a cross-sectional area (unit is cm ² ) when measuring the body electrolyte membrane, and L is an electrode. Distance between units (unit: cm). Note that S = 0.8 cm × 0.8 cm × π.
The measurement results are shown in Table 1.
Also, using the ionic conductivity (σ) calculated from the above measurement results, an Arrhenius plot with the reciprocal of the measurement temperature (1000 / T) on the horizontal axis and the logarithm of the ionic conductivity (log (σ)) on the vertical axis is shown. Created (FIG. 3).

As shown in Table 1, it was found that the electrolyte membranes of Examples 1 to 4 had higher ionic conductivity than the electrolyte membranes of Comparative Examples 1 to 3.
Moreover, as shown in FIG. 3, it turned out that the electrolyte membrane of Examples 1-4 has a small inclination compared with the electrolyte membrane of Comparative Examples 1-3, and there is little temperature dependence.

Claims (12)

The aliphatic polycarbonate resin containing the structural unit which has group represented by the following general formula ( 2 ).

(In the general formula (2), R ₁ is an electron withdrawing group, L is 1 or 2, m is than zero or a positive integer der, n is a positive integer, R ₂ represents hydrogen atom or an alkyl group der Ru.) The aliphatic polycarbonate resin according to claim 1 , wherein the alkyl group as R ₂ is an alkyl group having 1 to 3 carbon atoms. The aliphatic polycarbonate resin according to claim 1 , wherein R ₂ is a hydrogen atom or a methyl group. The aliphatic polycarbonate resin according to any one of claims 1 to 3 , wherein m is an integer of 0 or more and 5 or less. The aliphatic polycarbonate resin according to any one of claims 1 to 4 , wherein R ₁ is a group selected from the group consisting of a cyano group, a cyclic ether group, and a cyclic carbonate group. The R ₁ is any one of claims 1 to 5 , which is a cyano group, a 1,3-dioxolan-2-one-4-yl group, a 2-tetrahydrofuranyl group, or a 3-tetrahydrofuranyl group. The aliphatic polycarbonate resin described in 1. The aliphatic polycarbonate resin according to any one of claims 1 to 6 , wherein R ₁ is a cyano group. A solid electrolyte comprising the aliphatic polycarbonate resin according to any one of claims 1 to 7 and an alkali metal salt. The solid electrolyte according to claim 8 , wherein the alkali metal salt is a lithium salt. The solid electrolyte according to claim 9 , comprising at least one of lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide as the lithium salt. The solid electrolyte according to any one of claims 8 to 10 , wherein a molar ratio of metal to all carbonate groups (metal / total carbonate groups) in the aliphatic polycarbonate resin is 0.05 or more and 4 or less. Lithium ion secondary battery including a solid electrolyte according to any one of claims 11 to claim 8.

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