Resin composition containing polycarbonate resin, and electrolyte solution, film, and solid electrolyte containing same

Abstract

According to the present invention, it is possible to provide a resin composition containing a lithium salt and a polycarbonate resin containing a structural unit (A) derived from at least one component selected from the group consisting of bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP represented by the following structural formulae, the terminal structure of the polycarbonate resin contains a terminal structure derived from a polyalkylene glycol monoalkyl ether represented by general formula (1). (In general formula (1), R1 represents an alkylene group having 2-20 carbon atoms, R2 represents an alkyl group having 1-20 carbon atoms, and n represents an integer of 3-120. > # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a resin composition containing a polycarbonate resin, and an electrolyte solution, a membrane, and a solid electrolyte containing the same. Background Art

[0002] It is known that specific polycarbonate resin is dissolved in an organic solvent and used as ink or coating etc., and various organic solvents have been used. In addition, carbonate-based organic solvents such as dimethyl carbonate and ethylene carbonate are particularly widely used as electrolyte solvents for lithium ion batteries. However, when used as polycarbonate electrolyte, due to the low solubility of polycarbonate resin in carbonate-based organic solvents, it is difficult to obtain a coating, and therefore there is room for improvement. In order to solve such problems, various researches have been carried out, for example, it has been proposed to add methylene chloride as a solvent, make a colloidal solution, and then apply (patent documentation 1). However, even if methylene chloride is used, the solubility of polycarbonate resin in carbonate-based organic solvents is insufficient, and there is room for improvement.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-357533 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] The technical problem to be solved by the present invention is to obtain a resin composition capable of dissolving a lithium salt in a non-polar solvent and uniformly containing the lithium salt and a polycarbonate resin. Another technical problem to be solved by the present invention is to obtain an electrolyte containing the resin composition and having high electrical conductivity.

[0008] Technical solutions to technical problems

[0009] To address the above-mentioned technical problems, the inventors of the present invention conducted extensive research and discovered that by using a polycarbonate resin containing structural units derived from specific monomers and having a polyalkylene glycol chain as a terminal structure, lithium salts, which are difficult to dissolve in existing polycarbonate resins, can be dissolved in a non-polar solvent, thereby producing a resin composition uniformly containing the lithium salt and the polycarbonate resin. Furthermore, the inventors discovered that such a resin composition exhibits high electrical conductivity when used as an electrolyte, leading to the completion of the present invention.

[0010] That is, the present invention is as follows.

[0011] <1> A resin composition comprising a polycarbonate resin and a lithium salt, wherein:

[0012] The polycarbonate resin contains a structural unit (A) derived from at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP represented by the following structural formula, and

[0013] The terminal structure of the polycarbonate resin includes a terminal structure derived from a polyalkylene glycol monoalkyl ether represented by the following general formula (1).

[0014]

[0015] (In the general formula (1), R1 represents an alkylene group having 2 to 20 carbon atoms, R2 represents an alkyl group having 1 to 20 carbon atoms, and n represents an integer of 3 to 120.)

[0016] <2> The resin composition according to <1> above, wherein the resin composition contains 30.0 to 99.0% by mass of the polycarbonate resin relative to the total amount of the polycarbonate resin and the lithium salt.

[0017] <3> The resin composition according to <1> or <2> above, wherein the polyalkylene glycol monoalkyl ether has a number average molecular weight of 200 to 5,000.

[0018] <4> The resin composition according to any one of <1> to <3> above, wherein the polycarbonate resin has a viscosity average molecular weight (Mv) of 5,000 to 50,000.

[0019] <5> The resin composition according to any one of <1> to <4> above, wherein the resin composition contains 1.0 to 70% by mass of the lithium salt based on the total amount of the polycarbonate resin and the lithium salt.

[0020] <6> The resin composition according to any one of <1> to <5> above, wherein the lithium salt comprises at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

[0021] <7> An electrolyte solution containing the resin composition according to any one of <1> to <6> above.

[0022] <8> The electrolyte solution according to <7> above, wherein the electrolyte solution has an electrical conductivity of 1 to 500 μS / cm.

[0023] <9> A film comprising the resin composition according to any one of <1> to <6> above.

[0024] <10> A solid electrolyte comprising the resin composition according to any one of <1> to <6> above.

[0025] Effects of the Invention

[0026] The present invention can provide a resin composition capable of dissolving a lithium salt in a non-polar solvent and uniformly containing the lithium salt and a polycarbonate resin. The present invention can also provide an electrolyte solution containing the resin composition and having high electrical conductivity. DETAILED DESCRIPTION

[0027] Hereinafter, the present invention will be described in detail with reference to the embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with arbitrary modifications without departing from the gist of the present invention.

[0028] [Resin composition]

[0029] The resin composition of the present invention contains a polycarbonate resin having a specific structure and a lithium salt.

[0030] The resin composition of the present invention preferably contains 30.0 to 99.0 mass % of the polycarbonate resin, relative to the total amount of the polycarbonate resin and the lithium salt, more preferably 50.0 to 99.0 mass %, further preferably 60.0 to 99.0 mass %, further more preferably 70.0 to 99.0 mass %, and particularly preferably 75.0 to 96.0 mass %.

[0031] In addition, the resin composition of the present invention preferably contains 1.0 to 70 mass % of the lithium salt relative to the total amount of the polycarbonate resin and the lithium salt, more preferably 1.0 to 50 mass %, further preferably 1.0 to 40 mass %, further more preferably 1.0 to 30 mass %, and particularly preferably 4.0 to 25 mass %.

[0032] Polycarbonate resin

[0033] The polycarbonate resin used in the present invention contains a structural unit (A) derived from at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP represented by the following structural formula, and

[0034] The terminal structure of the polycarbonate resin includes a terminal structure derived from a polyalkylene glycol monoalkyl ether represented by the following general formula (1).

[0035]

[0036] In the general formula (1), R1 represents an alkylene group having 2 to 20 carbon atoms (preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms, further preferably 2 or 3 carbon atoms, particularly preferably 2 carbon atoms).

[0037] In the general formula (1), R2 represents an alkyl group having 1 to 20 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, further preferably 1 to 3 carbon atoms, and particularly preferably 1 carbon atom).

[0038] In the general formula (1), n ​​represents an integer of 3 to 120 (preferably 7 to 50, more preferably 8 to 25).

[0039] The number average molecular weight of the polyalkylene glycol monoalkyl ether used in the present invention is preferably 200 to 5,000, more preferably 300 to 4,000, even more preferably 300 to 2,000, even more preferably 300 to 1,200, and particularly preferably 400 to 1,000.

[0040] The viscosity average molecular weight (Mv) of the polycarbonate resin used in the present invention is preferably 5,000 to 50,000, more preferably 7,000 to 40,000, and particularly preferably 7,000 to 30,000. The viscosity average molecular weight (Mv) can be measured by the method described in the Examples below.

[0041] The polycarbonate resin used in the present invention preferably contains the structural unit (A) in an amount of 80 to 100 mol %, more preferably 90 to 100 mol %, and particularly preferably 100 mol % of all structural units constituting the polycarbonate resin.

[0042] The polycarbonate resin of the present invention may contain structural units other than the structural unit (A) within a range not impairing the effects of the present invention.

[0043] In a preferred embodiment of the present invention, when preparing a polycarbonate resin, a polyalkylene glycol monoalkyl ether represented by the above general formula (1) is used as a molecular weight modifier (terminal terminator), thereby providing a polyalkylene glycol chain as a terminal structure.

[0044] The polycarbonate resin used in the present invention can be produced by reacting at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP with a carbonate-forming compound. Therefore, the polycarbonate resin can be produced using known methods used to produce polycarbonate resins derived from bisphenol A, such as the direct reaction of bisphenols with phosgene (phosgene method) or the transesterification reaction of bisphenols with diaryl carbonates (transesterification method).

[0045] In the phosgene method, at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP is reacted with phosgene in the presence of an acid binder and a solvent. Examples of acid binders include pyridine or alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and examples of solvents include dichloromethane and chloroform. Furthermore, to promote the polycondensation reaction, a catalyst such as a tertiary amine such as triethylamine or a quaternary ammonium salt such as benzyltriethylammonium chloride is preferably added. Furthermore, a polyalkylene glycol monoalkyl ether represented by the general formula (1) is added as a molecular weight regulator (terminator). Furthermore, a small amount of an antioxidant such as sodium sulfite or sodium dithionite, or a branching agent such as phloroglucinol or isatin bisphenol may be added as desired. The reaction is generally carried out at a temperature between 0 and 150°C, preferably between 5 and 40°C. The reaction time is affected by the reaction temperature and is generally between 0.5 minutes and 10 hours, preferably between 1 minute and 2 hours. Furthermore, during the reaction, it is desirable to maintain the pH of the reaction system at 10 or higher.

[0046] On the other hand, in the transesterification method, at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP is mixed with a diaryl carbonate and reacted under reduced pressure and high temperature. Examples of diaryl carbonates include diphenyl carbonate, di-p-cresol carbonate, phenyl-p-cresol carbonate, di-p-chlorophenyl carbonate, and dinaphthyl carbonate. Two or more of these compounds can also be used in combination. The reaction is typically carried out at a temperature ranging from 150 to 350°C, preferably from 200 to 300°C. The degree of reduced pressure is preferably ultimately below 1 mmHg, and phenols derived from the diaryl carbonate produced by the transesterification reaction are distilled out of the reaction system. The reaction time is affected by factors such as the reaction temperature and the degree of reduced pressure, but is typically about 1 to 24 hours. The reaction is preferably carried out under an inert gas atmosphere such as nitrogen or argon. Furthermore, if desired, a molecular weight regulator, antioxidant, or branching agent may be added to the reaction.

[0047] Lithium salts

[0048] The lithium salt used in the present invention is not particularly limited, but preferably contains at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

[0049] [Electrolyte]

[0050] The electrolyte of the present invention preferably contains the above-mentioned resin combination and contains an organic solvent that can dissolve the above-mentioned polycarbonate resin and lithium salt. This organic solvent functions as a solvent for the electrolyte of the present invention. As specific examples of the organic solvent preferably used in the present invention, methylene chloride and various dialkyl carbonates (such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc.) can be cited. In the present invention, these can also be used in combination with two or more. Among these, methylene chloride, which has a relatively high solubility of the preferred polycarbonate resin, is preferred.

[0051] In a preferred embodiment of the present invention, the content of the organic solvent in the electrolyte solution is preferably 50 to 99.95% by mass, more preferably 60 to 99% by mass, further preferably 70 to 95% by mass, and particularly preferably 75 to 90% by mass.

[0052] The electrolyte solution of the present invention may further contain a rust preventive, an antioxidant, a dispersant, an ultraviolet absorber, a defoaming agent, a leveling agent, and the like, as needed.

[0053] The electrolyte of the present invention preferably has an electrical conductivity of 1 to 500 μS / cm at 20° C., more preferably 10 to 300 μS / cm, further preferably 15 to 250 μS / cm, and particularly preferably 15 to 230 μS / cm. The electrical conductivity can be measured by the method described in the Examples below.

[0054] [Solid Electrolyte]

[0055] The polymer gel electrolyte can be obtained by concentrating the electrolyte solution of the present invention and partially gelling it. The method for concentrating the electrolyte solution is not particularly limited, and examples thereof include methods such as partially air-drying and removing the solvent to form a surface-solidified high-viscosity liquid.

[0056] Alternatively, the electrolyte solution of the present invention can be irradiated with ultraviolet light at 365 nm for about 30 minutes at, for example, 50 mW / cm2 to cause gelation, thereby obtaining a solid electrolyte.

[0057] The solid electrolyte of the present invention is useful as an electrolyte material for Li polymer batteries and semi-solid batteries, and can particularly reduce the risk of leakage.

[0058] Example

[0059] Hereinafter, examples of the present invention will be illustrated together with comparative examples, and the content of the invention will be described in detail. However, the present invention is not limited to these examples.

[0060] 1) Conductivity

[0061] The conductivity of a mixed solution obtained by mixing polycarbonate resin, lithium salt (Li salt), and dichloromethane was measured using a conductivity meter.

[0062] Equipment used: AS650 waterproof conductivity meter manufactured by AS ONE Co., Ltd.

[0063] Measurement temperature: 20℃.

[0064] 2) Solubility of lithium salts (Li salt solubility)

[0065] A mixed liquid of a polycarbonate resin, a lithium salt (Li salt), and dichloromethane was stirred for 24 hours, and then the solubility of the lithium salt was evaluated by visual observation.

[0066] A: No dissolved residue of Li salt, transparent;

[0067] B: There is no dissolved residue of Li salt, but coloration occurs (white turbidity or brown or other opaque);

[0068] C: Li salt precipitates.

[0069] 3) Appearance of the resin composition

[0070] The appearance of the obtained resin composition was visually inspected to evaluate whether it was transparent.

[0071] 4) Viscosity average molecular weight (Mv) of polycarbonate resin

[0072] Measuring equipment: Ubbelohde capillary viscometer;

[0073] Solvent: dichloromethane;

[0074] Polycarbonate resin solution concentration: 0.5 g / dL;

[0075] Measurement temperature: 25℃.

[0076] The measurement was performed under the above conditions, and the intrinsic viscosity [η] in deciliter / g was determined using a Herkins constant of 0.45 and calculated using the following formula.

[0077] η=1.25×10 -4 ×Mv 0.83

[0078] (Synthesis example 1)

[0079] 83.0 g (0.34 mol) of 2,2-bis(4-hydroxyphenyl)-4-methylpentane (hereinafter referred to as "MIBK": manufactured by Honshu Chemical Industry Co., Ltd.) and 0.5 g of sodium dithionite were dissolved in a mixture of 440 ml of a 9.0 w / w% aqueous sodium hydroxide solution and 200 mL of pure water.

[0080] 300 ml of dichloromethane was added thereto, and the temperature was maintained at 15 to 25° C. with stirring, and then 42.5 g of phosgene was blown into the mixture over 30 minutes.

[0081] After the phosgene blowing is completed, 15.35 g of polyethylene glycol monomethyl ether 1000 (hereinafter referred to as "mPEG1000": manufactured by Tokyo Chemical Industry Co., Ltd.) is added as a molecular weight regulator (terminator) and vigorously stirred to emulsify the reaction solution. After emulsification, 0.5 ml of triethylamine is added and polymerization is carried out by stirring at 20-30°C for about 1 hour.

[0082] After the polymerization was completed, the reaction mixture was separated into an aqueous phase and an organic phase. The organic phase was neutralized with phosphoric acid and repeatedly washed with water until the conductivity of the washings (aqueous phase) reached 10 μS / cm or less. The resulting polymer solution was transferred to an aluminum dish and the solvent was evaporated on a hot plate. The resulting solid was further dried at 120°C for 24 hours to obtain a polymer solid.

[0083] The intrinsic viscosity of a 0.5 g / dl solution of the polymer in dichloromethane at 20°C was 0.44 dl / g, and the viscosity average molecular weight (Mv) was 21300. The obtained polymer was analyzed by infrared absorption spectroscopy. As a result, the peak at 1770 cm -1 The absorption of carbonyl group was observed at 1240 cm -1 Absorption due to ether bonds was observed at nearby positions, confirming that it was a polycarbonate resin having carbonate bonds (hereinafter referred to as "PC-1").

[0084] (Synthesis Examples 2 to 10)

[0085] Using the raw materials shown in Table 1 below, the same procedures as in Synthesis Example 1 were followed to obtain polycarbonate resins PC-2 to PC-10. The viscosity average molecular weights (Mv) of the obtained polycarbonate resins are shown in Table 1. The number average molecular weights of mPEG1000, mPEG550, and mPEG400 were 1000, 550, and 400, respectively.

[0086] [Table 1]

[0087] Table 1

[0088]

[0089] (Example 1)

[0090] 3 g of the polycarbonate resin (PC-1) obtained in Synthesis Example 1, 0.29 g of lithium salt (Li salt), and 12 g of dichloromethane were mixed in a disposable cup to prepare a mixed solution. The obtained mixed solution is useful as an electrolyte solution.

[0091] The obtained mixed solution was air-dried at 25° C. for 24 hours to remove dichloromethane, thereby obtaining a film-like resin composition. The obtained resin composition is useful as a membrane or solid electrolyte.

[0092] The results of the evaluation of the electrical conductivity and solubility of the lithium salt of the mixed solution (electrolyte) obtained above, and the appearance of the resin composition (solid electrolyte) obtained are shown in Table 2 below.

[0093] (Examples 2 to 27)

[0094] A mixed solution and a resin composition were obtained in the same manner as in Example 1 except that the raw materials shown in Table 2 were used. The results of the evaluation of the electrical conductivity and lithium salt solubility of the obtained mixed solution (electrolyte) and the appearance of the obtained resin composition (solid electrolyte) are shown in Table 2.

[0095] [Table 2]

[0096]

[0097] ※A uniform mixed solution was not obtained (Li salt precipitated in the mixed solution), and a uniform film (solid) was not obtained.

[0098]

Claims

1. A resin composition, characterized in that: The resin composition contains a polycarbonate resin and a lithium salt, The polycarbonate resin contains a structural unit (A) derived from at least one selected from bisphenol A, bisphenol C, bisphenol MIBK, bisphenol BPAF, bisphenol Z, and bisphenol AP represented by the following structural formula, and The terminal structure of the polycarbonate resin includes a terminal structure derived from a polyalkylene glycol monoalkyl ether represented by the following general formula (1): In the general formula (1), R1 represents an alkylene group having 2 to 20 carbon atoms, R2 represents an alkyl group having 1 to 20 carbon atoms, and n represents an integer of 3 to 120.

2. The resin composition according to claim 1, wherein: The resin composition contains 30.0 to 99.0% by mass of the polycarbonate resin relative to the total amount of the polycarbonate resin and the lithium salt.

3. The resin composition according to claim 1 or 2, wherein: The number average molecular weight of the polyalkylene glycol monoalkyl ether is 200 to 5,000.

4. The resin composition according to any one of claims 1 to 3, wherein: The viscosity average molecular weight Mv of the polycarbonate resin is 5,000 to 50,000.

5. The resin composition according to any one of claims 1 to 4, wherein: The resin composition contains 1.0 to 70% by mass of the lithium salt based on the total amount of the polycarbonate resin and the lithium salt.

6. The resin composition according to any one of claims 1 to 5, wherein: The lithium salt includes at least one selected from the group consisting of lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium tetrafluoroborate.

7. An electrolyte, characterized in that: A resin composition comprising the resin composition according to any one of claims 1 to 6.

8. The electrolyte according to claim 7, wherein: The conductivity of the electrolyte is 1 to 500 μS / cm.

9. A film, characterized in that: A resin composition comprising the resin composition according to any one of claims 1 to 6.

10. A solid electrolyte, characterized in that: A resin composition comprising the resin composition according to any one of claims 1 to 6.

Images