JP5826448B2 - Polymer composition containing ethylene oxide copolymer and lithium secondary battery - Google Patents

Description

  The present invention relates to an ethylene oxide copolymer having a specific crystallization temperature and a glass transition temperature, thereby suppressing an increase in the glass transition temperature due to the addition of a metal salt.

  Conventionally, ethylene oxide-based copolymers have been used as polymer materials such as adhesives, paints, sealing agents, elastomers, flooring, and other polyurethane resins, as well as hard, soft, or semi-rigid polyurethane resins, surfactants, and sanitary. It is used in a very wide range of applications such as products, deinking agents, lubricating oils, hydraulic oils, polymer electrolytes, etc. (see Non-Patent Document 1, for example).

In order to demonstrate the physical properties required for each application when used in these applications, in addition to optimization of the polymer such as molecular weight and copolymer composition, functions are generally given by blending various additives. Yes. There are various types of additives, but some additives interact with the polymer, so that the physical properties of the polymer may be changed in addition to imparting a desired function. Among them, a technique for adding a metal salt of an organic acid to a polymer in order to increase toughness is known (see, for example, Patent Documents 1 and 2).
Mitsuta Shibata, Masahiro Saito, Shin-ichi Akimoto, “Alkylene Oxide Polymers-Production Methods, Properties, and Applications”, Kaibundo, published on November 20, 1990, p. 25-128 JP 2003-73537 A (published March 12, 2003) Japanese Unexamined Patent Publication No. 7-206936 (released on August 8, 1995)

  However, the configurations of Patent Documents 1 and 2 cause a problem that it is difficult to design materials for the polymer and the composition. Specifically, when a metal salt is added to an ethylene oxide-based copolymer for antistatic purposes, the glass transition temperature of the composition is higher than the glass transition temperature of the polymer, resulting in viscosity and mechanical strength. Changes in physical properties will occur.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an ethylene oxide copolymer having a small increase in glass transition temperature when a metal salt is added, and a polymer composition containing the copolymer. And a lithium secondary battery including the polymer composition.

  The present inventor has intensively studied to solve the above problems. In the process, we thought that the increase in the glass transition temperature after the addition of the metal salt could be suppressed by weakening the interaction between the ethylene oxide copolymer and the metal ion. It was. As a result, it has been found that increasing the hydrophobicity of the copolymer is the most effective for weakening the interaction between the ethylene oxide copolymer and the metal ion. Further, the present inventors have found that the crystallization temperature and the glass transition temperature of the ethylene oxide copolymer before the addition of the metal salt have a strong correlation with the amount of change in the glass transition temperature before and after the addition of the metal salt. It came to complete.

  That is, the ethylene oxide copolymer according to the present invention is characterized by having a crystallization temperature of 20 ° C. or lower and a glass transition temperature of −64 ° C. or lower in order to solve the above problems.

  According to the above configuration, in order to lower the crystallization temperature and the glass transition temperature of the ethylene oxide copolymer, a hydrophobic monomer coexists during the polymerization of ethylene oxide, and the coexisting monomer (hereinafter referred to as “comonomer”). In addition to inhibiting the formation of ethylene oxide copolymer crystals derived from the chain of ethylene oxide, the structure derived from the ethylene oxide copolymer and the metal salt when the metal salt is added. The action is suppressed. Therefore, there is an effect that it is possible to provide an ethylene oxide copolymer having a small increase in glass transition temperature when a metal salt is added.

  The ethylene oxide copolymer according to the present invention preferably has a heat of crystallization of 60 mJ / mg or less.

  According to said structure, since the formation of the crystal | crystallization of the ethylene oxide type copolymer originating in the chain | strand of ethylene oxide is inhibited more, when a metal salt is added, interaction with a metal salt is suppressed more. Therefore, there is an additional effect that it is possible to provide an ethylene oxide-based copolymer with less increase in glass transition temperature when a metal salt is added.

  In addition, the ethylene oxide copolymer according to the present invention is preferably obtained by polymerizing a monomer composition containing 10 mol% or more of a comonomer.

  Furthermore, the ethylene oxide copolymer according to the present invention is preferably a random copolymer having a weight average molecular weight in the range of 20,000 to 500,000.

  The polymer composition according to the present invention is characterized by containing the ethylene oxide copolymer according to the present invention and an organic acid metal salt in order to solve the above problems.

  According to the said structure, since the ethylene oxide type copolymer which concerns on this invention is included, the difference of the glass transition temperature between an ethylene oxide type copolymer and a polymer composition is small. For this reason, there exists an effect that the glass transition temperature of a polymer composition can be designed easily based on the glass transition temperature of an ethylene oxide type copolymer.

  The lithium secondary battery according to the present invention is characterized by including the polymer composition according to the present invention in order to solve the above problems.

  Conventionally, polymer electrolytes used in lithium secondary batteries do not use flammable solvents, so they have been studied as highly safe all-solid electrolytes. Since its conductivity is inferior, its use has been limited to use at higher temperatures (60 ° C. or higher) than solvent-based batteries.

  In order to overcome such problems, a configuration in which a carbonate solvent is used together (JP 2007-35646 A, JP 2006-147279 A) and polymers having various special structures (the latest technology of polymer batteries) II p.108-p.126, supervision; see Seiji Kanamura, see CMC Publishing Co., Ltd.).

  When a polymer electrolyte is used in combination with a solvent, the risk of liquid leakage and the like can be reduced as well as the effect of improving the ionic conductivity, but the solvent is inherently flammable, so the safety expected of the polymer electrolyte Sex was sacrificed.

  In addition, in the case of using a polymer having a special structure, an effect of improving ionic conductivity is recognized, and an application as an all-solid electrolyte can be expected. Therefore, it has not reached practical use.

  On the other hand, the lithium secondary battery according to the present invention has been designed as a battery by focusing on the characteristics of the polymer and its organic acid metal salt composition without using a special monomer. It is not necessary to operate under a high temperature condition of 60 ° C. or higher, which has been considered essential for operation, and can be operated under a mild condition such as 40 ° C.

  That is, since the lithium secondary battery according to the present invention includes the ethylene oxide copolymer according to the present invention, the difference in glass transition temperature between the ethylene oxide copolymer and the polymer composition is small. Since the interaction between the system copolymer and the metal salt is suppressed, the ionic conductivity is excellent and the discharge capacity is high.

  For this reason, according to the said structure, the high temperature condition of 60 degreeC or more which was considered essential to operate | move as a battery until now becomes unnecessary, and there exists an effect that it can be operate | moved also on mild conditions.

  As described above, the ethylene oxide copolymer according to the present invention is characterized by a crystallization temperature of 20 ° C. or lower and a glass transition temperature of −64 ° C. or lower.

  For this reason, there is an effect that it is possible to provide an ethylene oxide copolymer with a small increase in the glass transition temperature after the addition of the metal salt.

  As described above, the polymer composition according to the present invention includes the ethylene oxide copolymer according to the present invention and an organic acid metal salt.

  For this reason, there exists an effect that the glass transition temperature of a polymer composition can be designed easily based on the glass transition temperature of an ethylene oxide type copolymer.

  The lithium secondary battery according to the present invention includes the polymer composition according to the present invention as described above.

  For this reason, there is an effect that it can be operated even under mild conditions.

  Hereinafter, the ethylene oxide copolymer according to the present invention (hereinafter sometimes referred to as the copolymer of the present invention) will be described in detail, but the scope of the present invention is not limited to these descriptions, and Other than the above examples, modifications can be made as appropriate without departing from the spirit of the present invention. In the present specification, “A to B” indicating a range indicates A or more and B or less.

  Further, various physical properties listed in the present specification mean values measured by the methods described in the examples described later unless otherwise specified.

(1) Ethylene oxide copolymer The ethylene oxide copolymer according to the present invention has a crystallization temperature of 20 ° C or lower and a glass transition temperature of -64 ° C or lower.

  The ethylene oxide copolymer according to the present invention has a crystallization temperature of 20 ° C. or lower, more preferably in the range of −20 to 18 ° C., and particularly preferably in the range of −15 to 15 ° C.

  The crystallization temperature can be adjusted by the length (molecular weight) of the ethylene oxide chain in the copolymer, and the crystallization temperature can be lowered by increasing the comonomer content.

  The ethylene oxide copolymer according to the present invention has a glass transition temperature of −64 ° C. or lower, more preferably in the range of −80 to −64 ° C., particularly preferably in the range of −70 to −65 ° C. Is within.

The glass transition temperature can be adjusted by the quantitative ratio of ethylene oxide and comonomer, similarly to the crystallization temperature. Moreover, when the glass transition temperature of the homopolymer of the comonomer contained in the copolymer is known in advance, for example, when there are two types of copolymerization monomers, the following formula 1 / Tg = w _A / Tg _A + w _B / Tg _B
(Wherein Tg is the glass transition temperature of the copolymer, Tg _A is the glass transition temperature of the homopolymer comprising comonomer A, w _A is the weight fraction in the copolymer of comonomer A, and Tg _B is comonomer B. The glass transition temperature of the homopolymer, w _B is the weight fraction in the copolymer of comonomer B. Here, each glass transition temperature in the formula is an absolute temperature, and w _A + w _B = 1.
Can be calculated.

  More specifically, for example, when the glass transition temperature of ethylene oxide (EO) homopolymer is −63 ° C. and the glass transition temperature of propylene oxide (PO) homopolymer is −75 ° C., the comonomer composition is weight. The glass transition temperature of the copolymer having a ratio of EO / PO = 90/10 is −64.2 ° C., and the glass transition temperature of the copolymer having a comonomer composition of EO / PO = 80/20 by weight is The glass transition temperature of the copolymer having a comonomer composition of EO / PO = 70/30 at a weight ratio of −65.3 ° C. is −66.5 ° C.

  Furthermore, the ethylene oxide copolymer according to the present invention preferably has a crystallization heat of 60 mJ / mg or less, more preferably in the range of 0 to 50 mJ / mg, and particularly preferably 5 to 40 mJ / mg. Is within the range.

  The heat of crystallization depends on the amount of molecular chains that have been crystallized, and if it is difficult to crystallize, the heat of crystallization can be reduced. Specifically, the heat of crystallization can be lowered by increasing the amount ratio of the comonomer or increasing the chain length of the side chain.

  When the upper limit of the preferable range of the crystallization temperature, glass transition temperature and crystallization heat is exceeded, the inhibition of crystal formation derived from the chain of ethylene oxide becomes insufficient, and the interaction between the ethylene oxide copolymer and the metal salt is insufficient. When the metal salt is added, the polymer is not sufficiently suppressed, and only a polymer equivalent to a conventional ethylene oxide copolymer can be obtained. On the other hand, if the value is lower than the lower limit value, the structure derived from the comonomer is excessively present and the hydrophobicity becomes too high. As a result, the affinity between the ethylene oxide copolymer and the metal salt decreases, and the metal salt becomes ethylene oxide. It becomes impossible to melt | dissolve in a type | system | group copolymer, and it becomes impossible to acquire the addition effect of a metal salt.

  Examples of the ethylene oxide copolymer include ethylene oxide and the following general formula (I):

(However, R ₁ is Ra (Ra is an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, a (meth) acryloyl group, and an alkenyl group having 1 to 16 carbon atoms. Or a CH ₂ —O—Re—Ra group (Re has a structure of — (CH ₂ —CH ₂ —O) _p —, where p is an integer from 0 to 10)).
And a copolymer obtained by copolymerizing a monomer composition containing at least one kind of a substituted oxirane compound having a structure represented by the formula: As the above R _1, the easiness of synthesis and the like, and more preferably Ra.

  Examples of the substituted oxirane compound represented by the general formula (I) include propylene oxide, 1,2-epoxybutane, 1,2-epoxyisobutane, 2,3-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2-epoxytetradecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, 1,2-epoxyeicosanecyclohexene Examples thereof include oxide and styrene oxide, methyl glycidyl ether, ethyl glycidyl ether, and ethylene glycol methyl glycidyl ether.

Examples of the case where the substituent R ₁ is a crosslinkable substituent include epoxybutene, 3,4-epoxy-1-pentene, 1,2-epoxy-5,9-cyclododecadiene, and 3,4-epoxy. -1-vinylcyclohexene, 1,2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate and glycidyl-4-hexanoate, or vinyl glycidyl ether, allyl glycidyl ether, 4-vinylcyclohexyl Glycidyl ether, α-terpenyl glycidyl ether, cyclohexenyl methyl glycidyl ether, 4-vinylbenzyl glycidyl ether, 4-allylbenzyl glycidyl ether, allyl glycidyl ether, ethylene glycol allyl glycidyl ether, ethylene glycol Lumpur vinyl glycidyl ether, diethylene glycol allyl glycidyl ether, diethylene glycol vinyl glycidyl ether, triethylene glycol allyl glycidyl ether, triethylene glycol vinyl glycidyl ether, oligoethylene glycol allyl glycidyl ether and oligoethylene glycol vinyl glycidyl ether. As described above, these may be used alone or in combination of two or more.

  In addition, a silicon-containing group such as trimethylsilyl or an epoxy compound having a fluorinated alkyl group is preferable because the hydrophobicity can be increased with a small addition amount.

  As the comonomer according to the present invention, it is preferable to use propion oxide or butylene oxide from the viewpoint of easy availability, control of reactivity, and efficient improvement of hydrophobicity. Moreover, when performing bridge | crosslinking introduction | transduction, it is preferable to use allyl glycidyl ether for the same reason.

  From the viewpoint of the above-mentioned ethylene oxide chain scission and hydrophobicity control, familiarity between the ethylene oxide copolymer and the metal salt (affinity) and the solubility of the metal salt in the ethylene oxide copolymer, the total amount of comonomer used is: It is preferably in the range of 1 to 30 mol% of the total monomers used for the polymerization. More preferably, it exists in the range of 5-28 mol%, Most preferably, it exists in the range of 10-20 mol%. The amount of the crosslinkable monomer is not particularly limited, and may be appropriately set so that necessary characteristics can be obtained. Moreover, a random copolymer is preferable in order to effectively cut the ethylene oxide chain by the comonomer to be copolymerized.

  The ethylene oxide copolymer according to the present invention is more preferably a copolymer composed of ethylene oxide / butylene oxide / allyl glycidyl ether.

  The monomer composition may contain not only ethylene oxide and the substituted oxirane compound but also other monomers. In addition, from the viewpoint of efficiently improving the hydrophobicity of the resulting copolymer, the substituted oxirane compound includes alkylene oxides such as propylene oxide, butylene oxide, 1,2-epoxypentane, and 1,2-epoxyhexane. It is more preferable to use

  Among the above-mentioned copolymers, particularly when used for a battery, from the viewpoint of versatility and polymerizability of the monomer, at least one comonomer selected from the group consisting of propylene oxide, butylene oxide, and allyl glycidyl ether; A copolymer with ethylene oxide is preferred.

  Considering the formation of crystals derived from the chain of ethylene oxide, the lower the molecular weight of the ethylene oxide copolymer, the lower the crystallization temperature, glass transition temperature, and crystallization heat. In order to exhibit these characteristics, the weight average molecular weight is preferably 5,000 or more. More preferably, it is in the range of 10,000 to 1,000,000, and particularly preferably in the range of 20,000 to 500,000. When exceeding the upper limit of the above preferred range, there arises a problem that handling becomes difficult due to the increase in viscosity regardless of the properties of the bulk / solution.

  The method for producing the ethylene oxide copolymer according to the present invention is not particularly limited, and a desired copolymer can be obtained by ring-opening polymerization of an oxirane monomer by a conventionally known method. What is necessary is just to select a polymerization catalyst and a polymerization solvent suitably.

  The polymerization catalyst is not particularly limited. For example, alkaline catalysts such as sodium hydroxide, potassium hydroxide, potassium alcoholate, sodium alcoholate, potassium carbonate and sodium carbonate, metals such as metal potassium and metal sodium, organic Preferred examples include an aluminum catalyst and an organic zinc catalyst.

  Examples of the polymerization solvent include aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; aliphatic carbonization such as heptane, octane, n-hexane, n-pentane, and 2,2,4-trimethylpentane. Hydrogen solvents; cycloaliphatic hydrocarbon solvents such as cyclohexane and methylcyclohexane; ether solvents such as diethyl ether, dibutyl ether and methyl butyl ether; solvents of ethylene glycol dialkyl ethers such as dimethoxyethane; THF (tetrahydrofuran) ), A cyclic ether solvent such as dioxane; an organic solvent not containing active hydrogen such as a hydroxyl group is preferable, and toluene and xylene are more preferable.

  When an ethylene oxide copolymer is produced using the polymerization catalyst and the polymerization solvent, the polymerization is performed while stirring the monomer composition in the solvent. As such a polymerization method, for example, a solution polymerization method, a precipitation polymerization method and the like are preferably mentioned, and among these, the solution polymerization method is more preferable because it is excellent in productivity. Furthermore, a solution polymerization method in which polymerization is performed while supplying a monomer composition as a raw material to a previously charged solvent is particularly preferable from the viewpoint of safety such as easy removal of reaction heat.

(2) Polymer composition The polymer composition according to the present invention contains the above-described ethylene oxide copolymer and an organic acid metal salt.

  The organic acid metal salt is not particularly limited, and a conventionally known substance can be used. Specifically, carboxylic acids such as acetic acid and trifluoroacetic acid; sulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid; acids such as NH compounds showing strong acidity such as dicyanotriazole and bis (trifluoromethylsulfonyl) imide Examples thereof include alkali metal salts (Li, Na, K) having a residue.

  Examples of the organic acid metal salt include lithium perfluoroalkylsulfonates such as lithium trifluoromethanesulfonate, lithium dicyanotriazolate, lithium bistrifluoromethylsulfonium imide, lithium difluorosulfonylimide, lithium hexafluorophosphate, lithium tetrafluoro. Examples thereof include lithium salts such as borate and lithium perchlorate, potassium salts such as potassium bistrifluoromethylsulfonium imide, and sodium salts such as sodium acetate. Among these, lithium bis (trifluoromethylsulfonyl) imide, lithium difluorosulfonylimide, lithium dicyanotriazolate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium trifluoromethanesulfonate are suitable for batteries. Lithium bis (trifluoromethylsulfonyl) imide, lithium difluorosulfonylimide, and lithium dicyanotriazolate can be particularly preferably used.

  The content of the ethylene oxide copolymer in the polymer composition is preferably in the range of 50 to 99% by weight, more preferably in the range of 60 to 95% by weight, particularly preferably 70 to 90% by weight. Within range. The content of the organic acid metal salt in the polymer composition is preferably in the range of 1 to 50% by weight, more preferably in the range of 5 to 40% by weight, and particularly preferably 10 to 30% by weight. Is within the range.

  The method for producing the polymer composition is not particularly limited. For example, as described in the examples described later, the above-described ethylene oxide copolymer and organic acid metal salt are dissolved in an organic solvent. And a method of removing the organic solvent. In this case, when the ethylene oxide copolymer has a reactive substituent such as an allyl group, the organic acid metal salt may be added to the ethylene oxide copolymer and then subjected to a crosslinking reaction.

  The crosslinking reaction may be performed, for example, by adding a radical photopolymerization initiator and then irradiating with ultraviolet rays.

  The ethylene oxide copolymer or polymer composition according to the present invention is not particularly limited. Specifically, for example, in addition to polyurethane resins such as adhesives, paints, sealing agents, elastomers, flooring materials, It is preferably used as a polymer material for a wide range of applications such as a soft or semi-rigid polyurethane resin, and further a surfactant, antistatic agent, sanitary product, deinking agent, lubricating oil, hydraulic fluid, polymer electrolyte, etc. it can.

  As shown above, the ethylene oxide copolymer according to the present invention includes, in other words, an ethylene oxide copolymer having a crystallization temperature of 20 ° C. or lower and a glass transition temperature of −64 ° C. or lower. At least one selected from adhesives, paints, sealants, elastomers, flooring materials, surfactants, deinking agents, lubricating oils, hydraulic fluids, antistatic agents, and electrolytes (hereinafter referred to as “adhesives”). is there. As a result, even if a metal salt is included, the change in the glass transition temperature is small compared to the ethylene oxide copolymer before the addition of the metal salt. Therefore, based on the glass transition temperature of the ethylene oxide copolymer. A glass transition temperature of an adhesive or the like can be easily designed.

  The adhesive or the like preferably has a crystallization heat of 60 mJ / mg or less. Thereby, based on the glass transition temperature of an ethylene oxide type copolymer, the glass transition temperature of adhesives etc. can be designed more accurately.

  Furthermore, the polymer composition according to the present invention is, in other words, an adhesive or the like comprising the ethylene oxide copolymer according to the present invention and an organic acid metal salt.

(3) Lithium Secondary Battery The lithium secondary battery according to the present embodiment is mainly composed of an electrolyte, a positive electrode, and a negative electrode, and includes the above-described polymer composition. Specifically, in the lithium secondary battery according to the present embodiment, the above-described polymer composition is included in at least one of the electrolyte, the positive electrode, and the negative electrode, and the above-described polymer composition is included in the electrolyte. More preferred.

  The lithium secondary battery according to the present embodiment can be manufactured, for example, by stacking in order of negative electrode / electrolyte / positive electrode.

[Positive electrode]
The positive electrode can be produced, for example, by applying a slurry obtained by dissolving and dispersing a material constituting the positive electrode in a solvent onto a current collector, and then drying and pressure-molding the slurry.

  In producing the positive electrode, materials such as a positive electrode active material, a conductive additive, and a solvent are used in addition to the polymer composition. Examples of the positive electrode active material include lithium-manganese composite oxide, lithium cobaltate, vanadium pentoxide, olivine-type iron phosphate, polyacetylene, polypyrene, polyaniline, polyphenylene, polyphenylene sulfide, polyphenylene oxide, polypyrrole, polyfuran, polyazulene, and the like. .

  Moreover, carbon materials, such as ketjen black, acetylene black, and graphite, can be used for the conductive assistant. The positive electrode composition can be obtained by kneading the polymer composition, the positive electrode active material, and the conductive additive without solvent, but the positive electrode composition can be easily obtained by using a solvent.

  As the solvent at this time, an aromatic hydrocarbon compound such as toluene or a polar compound containing no active hydrogen such as acetonitrile, acetone or tetrahydrofuran can be used.

  The proportion of the ethylene oxide copolymer in the slurry composed of the above materials is preferably 15 to 60% by weight, more preferably 20 to 55% by weight, and further preferably 25 to 50% by weight with respect to the slurry. .

  When the ratio of the ethylene oxide copolymer is lower than the above range, productivity is extremely lowered, which is not preferable. On the other hand, when the ratio is higher than the above range, the viscosity becomes high, mixing and stirring become difficult, and the uniform dispersibility between the positive electrode active material and the conductive additive may be reduced.

  The ratio of the organic acid metal salt in the polymer composition is such that the molar ratio (O / Li) between the oxygen atom of the ethylene oxide copolymer and the lithium atom in the organic metal salt is 1 to 36. More preferably, it is 3-33, More preferably, it is 6-30.

  If the amount of the organic acid metal salt is less than the above range, the ionic conductivity may be lowered and the performance as a battery may be deteriorated. There is a risk that the effect of increasing the efficiency is not obtained and the economy is inferior.

  Further, the positive electrode active material is preferably 0.1 to 50 times by weight, more preferably 0.3 to 20 times, still more preferably 0.5 to 10 times the weight of the ethylene oxide copolymer. . If the amount of the positive electrode active material is less than the above range, the function as the positive electrode may not be sufficiently exhibited, and if it exceeds the above range, it may be difficult to form the positive electrode material.

  The conductive auxiliary agent is preferably 0.1 to 20% by weight, more preferably 1 to 15% by weight with respect to the positive electrode active material. If the amount of the conductive assistant is less than the above range, the positive electrode may have insufficient conductivity, and the positive electrode performance may not be exhibited. If the amount is larger than the above range, it may be difficult to form the positive electrode material.

  The positive electrode composition slurry prepared as described above is applied onto a current collector and dried, and then subjected to pressure molding to produce a positive electrode. A metal foil such as an aluminum foil can be used for the current collector.

〔Electrolytes〕
In order to prevent a short circuit between the positive electrode and the negative electrode, the electrolyte is preferably used in the form of a crosslinked product of the polymer composition.

  As a method for producing the above film, a polymer and an organic acid lithium salt are formed into a thin film by kneading and extrusion, and then subjected to a crosslinking reaction utilizing the reactivity of the polymer, or the polymer and the organic acid lithium salt are mixed with a solvent. For example, the film obtained by coating and drying in a sheet form such as Teflon (registered trademark) after being dissolved in the film can be used.

  At this time, an aromatic hydrocarbon compound such as toluene or a polar compound containing no active hydrogen such as acetonitrile, acetone or tetrahydrofuran can be used as the solvent.

  The amount of the organic metal salt used in the polymer composition is such that the molar ratio (O / Li) between the oxygen atom in the ethylene oxide copolymer and the lithium atom in the organic metal salt is 1 to 36. More preferably, it is 3-33, More preferably, it is 6-30.

  If the amount of the organic metal salt is less than the above range, the ionic conductivity may be reduced, and the performance of the battery may be deteriorated. There is a risk that the effect of enhancing the property cannot be obtained and the economy is inferior.

  In producing the electrolyte membrane, it is possible to add fine particles such as Aerosil (registered trademark) in order to improve the handleability such as the strength of the membrane.

[Negative electrode]
Examples of the negative electrode material include intercalation compounds in which lithium is occluded between graphite or carbon layers, lithium metal, lithium-lead alloys, lithium-silicon alloys, lithium-zinc alloys, artificial graphite such as graphite and mesocarbon microbeads, titanium Examples thereof include compounds in which lithium such as lithium acid is occluded in the crystal structure. Moreover, the utilization as a diaphragm of ion electrodes of positive ions, such as an alkali metal ion, Cu ion, Ca ion, and Mg ion, using high ion conductivity is also considered.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to a following example. Hereinafter, for convenience, “part by weight” may be simply referred to as “part”, “time” may be simply referred to as “h”, and “liter” may be simply referred to as “L”. Further, “weight” may be written as “wt” (for example, “wt%” is written as “wt%”, and “weight / weight” is written as “wt / wt”).

  Conditions for pretreatment of raw materials used and various measurements in the following polymerization examples, examples and comparative examples are shown below. Thus, about the reaction mixture obtained in Examples 1-4 and Comparative Examples 1-7, evaluation and measurement shown below were performed. These results are shown in Tables 1 and 2. The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer contained in each reaction mixture are also shown in Table 1.

[Dehydration treatment with molecular sieve]
After adding 10 wt% molecular sieve (Union Showa Co., Ltd., product name: molecular sieve (type: 4A 1.6)) to the raw material monomer and solvent to be dried, the atmosphere is replaced with nitrogen and 12 hours at room temperature. It was left above.

[Measurement of weight average molecular weight (Mw), molecular weight distribution (Mw / Mn)]
A GPC apparatus (manufactured by Tosoh Corporation, product name: HLC-) was prepared by dissolving a reaction mixture (including an ethylene oxide copolymer) obtained after the reaction in a predetermined solvent and then using a standard molecular weight sample of polyethylene oxide. 8220 GPC), the weight average molecular weight (Mw) and the molecular weight distribution (Mw / Mn) were measured.

[Thermal analysis: glass transition temperature, crystallization temperature, heat of crystallization, melting point]
Using a differential thermal analyzer, the glass transition temperature, crystallization temperature, and heat of crystallization of the polymer were measured in the following temperature pattern. The ethylene oxide copolymer used as a sample was prepared by drying the obtained reaction mixture at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the reaction mixture.

  Temperature pattern: Analyzing device (Seiko Denshi Kogyo Co., Ltd., product name: Thermal analyzer SSC5200H system) Rapid heating (rapid heating) to 100 ° C to melt the polymer once, then quenching to -150 ° C to crystallize The melting point was determined from the melting behavior of crystals when the polymerized polymer was heated to 100 ° C. at 5 ° C./min. Furthermore, the crystallization temperature was calculated | required from the exothermic peak accompanying the crystallization which appears when cooling from 100 degreeC to -20 degreeC at 5 degrees C / min.

[Battery evaluation]
The work in the battery evaluation was performed in an environment in which the dew point was controlled to −45 ° C. or lower unless otherwise specified.

(1) Preparation of positive electrode (i) Add 12.5 parts of ethylene oxide copolymer to a solution in which 2.6 parts of lithium bis (trifluoromethylsulfonyl) imide is dissolved in 58 parts of acetonitrile in a sealed container, and Stirring to obtain a uniform polymer solution.

(Ii) 27 parts of V ₂ O ₅ (manufactured by Shinsei Kagaku) / Ketjen Black (Lion, V ₂ O ₅ / Ketjen Black = 95 wt% / 5 wt%) is added to the solution obtained in (i), The slurry of the positive electrode composition obtained by mixing and dispersing with a homomixer was filtered through a pressure filter equipped with a 150 mesh wire mesh, defoamed, and then a current collector (carbon-coated Aluminum foil (manufactured by InteliCoat) ( Width: 202mm with a 6mm uncoated edge)

  (Iii) After drying at 60 ° C. for 30 minutes using a vacuum dryer, pressure molding was performed at 60 ° C. and 30 MPa for 5 minutes using a desktop press.

(2) Production of polymer electrolyte membrane (SPE) (i) 2.5 parts of lithium bis (trifluoromethylsulfonyl) imide and 0.05 part of Yoshinox BB (trade name, manufactured by API Corporation) in a sealed container To a solution dissolved in 18 parts of acetonitrile, 0.1 part of ESACURE KTO46 (manufactured by Sartomer) was added and further stirred to obtain a uniform solution.

(Ii) Add 10 g of ethylene oxide copolymer, shield the container from light with aluminum foil, and filter the polymer solution obtained by thorough stirring. Then, coat on Teflon (registered trademark) sheet. Then, it was dried at 60 ° C. for 30 minutes using a vacuum dryer, and UV-irradiated to crosslink the SPE film (illuminance: 300 mW / cm ² , 450 W × 40 seconds, room temperature to 60 ° C.).

(3) Cell assembly (i) The polymer electrolyte membrane, the positive electrode membrane, and the Li foil respectively produced by the operations (1) and (2) were punched with a punch. Here, for the positive electrode film, the weight of the current collector with the cathode was measured with a precision balance.

  (Ii) The layers were laminated in the order of Li foil / SPE / positive electrode film, taking care not to allow air to enter between the layers.

  (Iii) The laminate was placed in a coin battery and crimped with a caulking machine while crimping with a spring.

(4) Battery evaluation The produced coin battery is installed in a thermostat set at 40 ° C., and charging / discharging is repeated at a constant current of c / 8 three times at c / 24, and the charge / discharge amount is recorded. did.

[Example 1]
A 1 L reactor equipped with Max Blend wing (manufactured by Sumitomo Heavy Industries, Ltd.) and an addition port was washed with a solvent, followed by heat drying and nitrogen substitution. In this reactor, 286.5 parts of toluene dehydrated with molecular sieves and 0.54 parts of t-butoxy potassium (20 wt% tetrahydrofuran (THF) solution) as a reaction initiator (based on the total monomer charge) 375 ppm) in this order. After the charging, nitrogen substitution in the reactor was performed, and the reactor was pressurized with nitrogen until the pressure in the reactor reached 0.3 MPa, and the temperature was raised using an oil bath while rotating and stirring the Max Blend blade.

  After confirming that the internal temperature reached 90 ° C., a monomer mixture consisting of ethylene oxide, butylene oxide and allyl glycidyl ether dehydrated by molecular sieve (mixing ratio (wt / wt): butylene oxide / allyl glycidyl) Ether = 15/3) at a rate of 47 parts / h and 10.3 parts / h for 2.5 hours, respectively, followed by a supply rate of 23.5 parts / h and 5.15 parts, respectively. The amount was then supplied quantitatively for 5 hours (total supply amount of ethylene oxide: 235 parts, supply amount of monomer mixture: total 51.5 parts).

  During the supply, the reaction was carried out at a temperature in the range of 100 ° C. ± 5 ° C. while monitoring and controlling the increase in internal temperature and the increase in internal pressure due to polymerization heat. After completion of the supply, the reaction mixture was further aged in the range of 90 ° C. or higher and 100 ° C. or lower for 5 hours to obtain a reaction mixture containing the ethylene oxide copolymer (A-1).

  As a result of performing molecular weight measurement and thermal analysis of the ethylene oxide copolymer (A-1) by the method described above, the weight average molecular weight Mw is 89,000, the molecular weight distribution Mw / Mn is 1.68, and glass The transition temperature (Tg) is −65.9 ° C., the crystallization temperature (Tc) is 10.6 ° C., the crystallization heat (ΔTc) is 10.5 mJ / mg, and the melting point (Tm) is 30. It was 5 ° C. Moreover, the result of battery evaluation is shown in FIG.

[Comparative Example 1]
A monomer mixture composed of ethylene oxide and butylene oxide and allyl glycidyl ether (mixing ratio (wt / wt): butylene oxide / allyl glycidyl ether = 8/3) was 51 parts / h and 6.3 parts / h, respectively. After quantitatively supplying at a supply rate for 2.5 hours, the supply rate was decreased to 25.5 parts / h and 3.15 parts / h, respectively, and further supplied quantitatively for 5 hours (Ethylene oxide supply amount: 255 in total) Parts and monomer mixture supply amount: 31.5 parts in total), and the same operation as in Example 1 was performed to obtain a reaction mixture containing an ethylene oxide copolymer (A-2).

  As a result of performing molecular weight measurement and thermal analysis by the method described above, the weight average molecular weight Mw is 91,000, the molecular weight distribution Mw / Mn is 1.86, and the glass transition temperature (Tg) is −62.1 ° C. The crystallization temperature (Tc) was 21.1 ° C., the crystallization heat (ΔTc) was 66.8 mJ / mg, and the melting point (Tm) was 36.9 ° C. Moreover, the result of battery evaluation is shown in FIG.

[Comparative Example 2]
The same procedure as in Comparative Example 1 was carried out except that the supply conditions of ethylene oxide and monomer mixture (mixing ratio (wt / wt): butylene oxide / allyl glycidyl ether = 8/3) were as follows. A reaction mixture containing the copolymer (A-3) was obtained.

  As a result of performing molecular weight measurement and thermal analysis by the method described above, the weight average molecular weight Mw is 104,000, the molecular weight distribution Mw / Mn is 1.70, and the glass transition temperature (Tg) is −62.5 ° C. The crystallization temperature (Tc) was 20.6 ° C., the crystallization heat (ΔTc) was 93.8 mJ / mg, and the melting point (Tm) was 48.0 ° C. Moreover, the result of battery evaluation is shown in FIG.

<Supply conditions>
After 30 minutes from the start of supplying ethylene oxide at 51 parts / h, a monomer mixture (mixing ratio (wt / wt): butylene oxide / allyl glycidyl ether = 8/3) was supplied at 7.5 parts / h. Supply started at speed. Further, 2.5 hours after the start of ethylene oxide supply, the supply rate was reduced to 25.5 parts / h and 3.15 parts / h, respectively, and further supplied quantitatively for 5 hours (amount of ethylene oxide supplied: 255 parts in total, Supply amount of monomer mixture: 31.5 parts in total).

[Example 2]
The reaction mixture obtained in Example 1 was dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the reaction mixture to obtain an ethylene oxide copolymer (A-1).

  9.02 parts of the resulting ethylene oxide copolymer (A-1) 0.98 parts of lithium dicyanotriazolate (LiDCTA), 50.00 parts of acetonitrile, and photo radical polymerization initiator Irgacure 651 (manufactured by Nagase Sangyo Co., Ltd.) 0.1 part) was added and dissolved by stirring. The obtained mixture solution was applied on a Teflon (registered trademark) sheet to a thickness of 50 μm, and then dried at 80 ° C. for 2 hours with a vacuum dryer to remove volatile components in the coating film.

  After the drying, UV irradiation is performed (UV irradiation machine: Ushio Electric Co., Ltd., light source device for printing URM-100), UV irradiation conditions: (output) 450 W, (irradiation time) 40 seconds), and consists of a polymer composition. A membrane was obtained. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −51.1 ° C. and the crystallization temperature (Tc) was −7.5 ° C. The heat (ΔTc) was 42.7 mJ / mg and the melting point (Tm) was 18.2 ° C.

[Comparative Example 3]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 2 was performed except that the reaction mixture obtained in Comparative Example 1 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −46.1 ° C. and the crystallization temperature (Tc) was −1.2 ° C. The heat (ΔTc) was 81.9 mJ / mg and the melting point (Tm) was 34.3 ° C.

Example 3
The reaction mixture obtained in Example 1 was dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the reaction tail mixture to obtain an ethylene oxide copolymer (A-1).

  8.00 parts of the obtained ethylene oxide copolymer (A-1), 2.00 parts of lithium bistrifluoromethylsulfonium imide (LiTFSI), 50.00 parts of acetonitrile, and photoradical polymerization initiator Irgacure 651 (Nagase Sangyo Co., Ltd.) 0.1 part) was added and dissolved by stirring. The obtained mixture solution was applied on a Teflon (registered trademark) sheet to a thickness of 50 μm, and then dried at 80 ° C. for 2 hours with a vacuum dryer to remove volatile components in the coating film.

  After the drying, UV irradiation is performed (UV irradiation machine: Ushio Electric Co., Ltd., light source device for printing URM-100), UV irradiation conditions: (output) 450 W, (irradiation time) 40 seconds), and consists of a polymer composition. A membrane was obtained. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −59.7 ° C. and the crystallization temperature (Tc) was −23.9 ° C. The heat (ΔTc) was 9.7 mJ / mg and the melting point (Tm) was 14.3 ° C.

[Comparative Example 4]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 3 was performed except that the reaction mixture obtained in Comparative Example 1 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −52.2 ° C., the crystallization temperature (Tc) was 1.0 ° C., and the heat of crystallization (ΔTc) was 4.6 mJ / mg, and the melting point (Tm) was 26.8 ° C.

[Comparative Example 5]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 3 was performed except that the reaction mixture obtained in Comparative Example 2 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −45.4 ° C. and the crystallization temperature (Tc) was −4.8 ° C. The heat (ΔTc) was 29.6 mJ / mg and the melting point (Tm) was 40.4 ° C.

Example 4
The reaction mixture obtained in Example 1 was dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the reaction mixture to obtain an ethylene oxide copolymer (A-1).

  To 7.83 parts of the obtained ethylene oxide copolymer (A-1), 2.17 parts of potassium bistrifluoromethylsulfonium imide (KTSFI) and 50.00 parts of acetonitrile were added and dissolved by stirring. After the obtained mixture solution is applied on a Teflon (registered trademark) sheet at a thickness of 50 μm, it is dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the coating film, thereby forming a film comprising a polymer composition Got. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −58.3 ° C. and the crystallization temperature (Tc) was −32.7 ° C. The heat (ΔTc) was 136.0 mJ / mg and the melting point (Tm) was 39.3 ° C.

[Comparative Example 6]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 4 was performed except that the reaction mixture obtained in Comparative Example 1 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −48.5 ° C. and the crystallization temperature (Tc) was −28.4 ° C. The heat (ΔTc) was 90.7 mJ / mg and the melting point (Tm) was 39.1 ° C.

[Comparative Example 7]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 4 was carried out except that the reaction mixture obtained in Comparative Example 2 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −48.0 ° C. and the crystallization temperature (Tc) was −23.1 ° C. The heat (ΔTc) was 117.0 mJ / mg and the melting point (Tm) was 40.1 ° C.

Example 5
The reaction mixture obtained in Example 1 was dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the reaction tail mixture to obtain an ethylene oxide copolymer (A-1).

1 part of sodium acetate (CH ₃ COONa) and 50.00 parts of acetonitrile were added to 9 parts of the obtained ethylene oxide copolymer (A-1) and dissolved by stirring. The obtained mixture solution was applied on a Teflon sheet at a thickness of 50 μm, and then dried at 80 ° C. for 2 hours with a vacuum drier to remove volatile components in the coating film to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −62.2 ° C. and the crystallization temperature (Tc) was −29.0 ° C. The heat (ΔTc) was 138.0 mJ / mg and the melting point (Tm) was 39.1 ° C.

[Comparative Example 8]
Instead of using the reaction mixture obtained in Example 1, the same operation as in Example 5 was performed except that the reaction mixture obtained in Comparative Example 1 was used to obtain a film made of the polymer composition. As a result of thermal analysis of the film made of the obtained polymer composition, the glass transition temperature (Tg) was −57.3 ° C. and the crystallization temperature (Tc) was −32.8 ° C. The heat (ΔTc) was 87.3 mJ / mg and the melting point (Tm) was 39.1 ° C.

  The above results are shown in Tables 1 and 2 below.

  As shown in Tables 1 and 2, when the same organic acid metal salt was used, the ethylene oxide copolymer (A-1) obtained in Example 1 was the ethylene oxide type obtained in Comparative Examples 2 and 3. It was confirmed that the increase in Tg was small compared to the copolymers (A-2) and (A-3). Particularly, in Example 3, the Tg change width is about 1/3 to 3/5 as compared with Comparative Examples 4 and 5, and in Example 3, the Tg change width is about 35-60 compared with Comparative Examples 4 and 5. In Example 4, compared with Comparative Examples 6 and 7, the Tg variation range was around 50%.

  In general, in order to lower the glass transition temperature by 1 ° C., an ethylene oxide copolymer needs to be copolymerized by adding about 5 to 10 wt% of a comonomer to ethylene oxide (for example, propylene oxide is copolymerized with polyethylene oxide). In this case, in order to lower the glass transition temperature by 1 ° C., it is necessary to copolymerize the monomer by containing about 10% by weight of propylene oxide).

  That is, since the amount of comonomer copolymerized at the time of polymerization can be suppressed even if the increase width of the glass transition temperature is only suppressed by 1 ° C., from the increase suppression effect of the glass transition temperature shown in the above-described Examples. As can be seen, the ethylene oxide copolymer according to the present invention has a high degree of freedom in molecular design, and has an advantageous effect as compared with conventional ethylene oxide copolymers.

  The polymer composition of Example 1 can be used as a lubricating oil, a working fluid, and an electrolyte. The film made of the polymer composition of Examples 2 to 5 includes an antistatic sheet, an electrolyte, and the like. , Adhesives, paints, sealants, elastomers, and flooring.

  In the above applications, adhesiveness, cohesive force, and resistance (conductivity) are important performances, but the temperature dependence of each performance (adhesiveness, cohesive force, and resistance) is small as the glass transition temperature decreases. Therefore, it can be expected to show performance in a wide temperature range regardless of the season.

  In addition, as shown in FIG. 1, the battery produced using the ethylene oxide copolymer of Example 1 is higher in discharge than the battery produced using the ethylene oxide copolymer of Comparative Examples 1 and 2. Showed capacity. In particular, the difference tended to increase as the number of charge / discharge cycles increased.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Since the ethylene oxide copolymer of the present invention has a crystallization temperature of 20 ° C. or lower and a glass transition temperature of −64 ° C. or lower, there is little increase in the glass transition temperature when a metal salt is added. For this reason, it can be suitably used for adhesives, paints, sealing agents, elastomers, flooring materials, lubricating oils, hydraulic fluids, electrolytes, and the like.

It is a graph which shows the relationship of the discharge capacity with respect to the cycle number of the battery produced using the ethylene oxide type copolymer obtained in the Example.

Claims (5)

The crystallization temperature obtained from the exothermic peak accompanying crystallization that appears when cooling from 100 ° C to -20 ° C at 5 ° C / min is -20 ° C or higher and 20 ° C or lower, and the glass transition temperature is -150 ° C or higher. A copolymer of ethylene oxide and at least one comonomer selected from the group consisting of propylene oxide, butylene oxide and allyl glycidyl ether, having a temperature of −64 ° C. or lower, and the comonomer is 10 mol% or more and 20 mol% An ethylene oxide copolymer comprising a polymer of a monomer composition contained within the following range, and a polymer composition comprising an organic acid metal salt, the above described glass transition temperature of the ethylene oxide copolymer A polymer composition characterized in that the glass transition temperature rise of the polymer composition is 3.7 to 7.6 ° C.   The heat of crystallization determined from the exothermic peak accompanying crystallization that appears when the ethylene oxide copolymer is cooled from 100 ° C. to −20 ° C. at 5 ° C./min is from 0 mJ / mg to 60 mJ / mg. The polymer composition according to claim 1.   The polymer composition according to claim 1 or 2, wherein the ethylene oxide copolymer is a random copolymer having a weight average molecular weight in the range of 20,000 or more and 500,000 or less.   The polymer composition according to any one of claims 1 to 3, which is for a lithium secondary battery.   A lithium secondary battery comprising the polymer composition according to claim 1.

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