JPWO2019021810A1 - Separation membrane for non-aqueous electrolyte battery and non-aqueous electrolyte battery using the same - Google Patents

Abstract

One aspect of the present invention relates to a separation membrane for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery using the same, which comprises a polymer compound having a carboxylate group in the molecule.

Description

  TECHNICAL FIELD The present invention relates to a separation membrane for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery using the same.

  2. Description of the Related Art In recent years, mobile terminals such as mobile phones, laptop computers, and pad type information terminal devices have been remarkably spread. A lithium ion secondary battery is often used as a secondary battery used as a power source of these portable terminals. Since mobile terminals are required to have more comfortable portability, they have been used in various fields rapidly as they have become smaller, thinner, lighter, and have higher performance. This trend continues even now, and batteries used for mobile terminals are required to be smaller, thinner, lighter, and have higher performance.

  Furthermore, the movement of using non-aqueous electrolyte batteries is spreading to large-sized equipment such as electric vehicles, hybrid vehicles, and electric vehicles. Therefore, performance such as high capacity and charging/discharging characteristics at large current is required, but since it is a non-aqueous electrolyte battery, it may have a higher risk of smoking, ignition, bursting, etc. compared to water-based batteries. It is known and requires improved safety.

In a non-aqueous electrolyte battery such as a lithium ion secondary battery, a positive electrode and a negative electrode are installed via a separation membrane (separator), and LiPF ₆ , LiBF ₄ LiTFSI (lithium (bistrifluoromethylsulfonylimide)), LiFSI (lithium ( It has a structure in which a lithium salt such as bisfluorosulfonylimide)) is stored in a container together with an electrolytic solution in which an organic liquid such as ethylene carbonate is dissolved.

  Therefore, the risk of smoking increases due to temperature rise due to external heat, overcharge, internal short circuit, external short circuit, and the like. These can be prevented to some extent by an external protection circuit. Further, the shutdown function of the separator can also suppress the temperature rise of the battery.

  Up to now, for example, a porous film of polyolefin resin has often been used as the non-aqueous electrolyte battery separation membrane. This porous film has a role of maintaining safety (shutdown function) by melting when the temperature inside the battery reaches around 120° C., closing the pores and blocking the flow of current and ions. .. However, if the temperature rises due to external heat or if a chemical reaction occurs inside the battery due to the temperature rise, the battery temperature may rise further even if the shutdown function works, and the battery temperature may reach 150°C or higher. is there. In such a case, the porous film may shrink, causing an internal short circuit, which may cause ignition or the like.

  For such a problem, by providing a coating layer that is highly filled with an inorganic filler on a porous film of a polyolefin resin, abnormal heat generation occurs, exceeding the shutdown temperature, even when the temperature continues to rise It has been reported that a short circuit between both electrodes can be prevented (for example, Patent Document 1).

  However, when particles or a binder material are laminated on the porous film, the internal resistance of the electric element is increased, the output characteristics are deteriorated, or the capacity is rapidly reduced as the charge/discharge cycle progresses, which shortens the cycle life. There was a problem. Further stacking causes an increase in production cost and a decrease in productivity.

  In addition, from the viewpoint of safety, a polymer solid electrolyte in which an electrolyte is uniformly solid-dissolved in a polymer has been proposed (for example, Patent Document 2), but the polymer solid electrolyte is Although the ionic conductivity is lower than that of the liquid-added electrolyte and the improvement is progressing, there is a problem in practical use.

  As described above, it is difficult to produce a separation membrane which has high safety, suppresses an increase in internal resistance due to a separator, improves battery characteristics such as battery capacity, particularly lowers resistance, and has high productivity. Met.

  The present invention has been made in view of the above-mentioned problems, and has a high heat resistance and a low resistance, and a separation membrane for a non-aqueous electrolyte battery excellent in productivity and an electric element (non-aqueous electrolyte battery) using the same. The purpose is to provide.

JP, 2007-280911, A Japanese Patent No. 4888366

  As a result of intensive studies to solve the above problems, the present inventors have found that the above-mentioned object can be achieved by using a separation membrane having the following structure, and the present invention is further studied based on this finding. completed.

  That is, the battery separation membrane according to one aspect of the present invention is characterized by containing a polymer compound having a carboxylate group in the molecule.

  According to the present invention, it is possible to provide a safe and low-resistance separator for a non-aqueous electrolyte battery and an electric element (non-aqueous electrolyte battery) using the same.

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

  In the present embodiment, the separation membrane for a non-aqueous electrolyte battery (hereinafter, also simply referred to as a separation membrane) means that the positive electrode and the negative electrode in the non-aqueous electrolyte battery are separated from each other, and the electrolyte is passed or retained to separate the positive electrode and the negative electrode. Means a film having an ion transport property that allows ions to pass between them.

(Polymer compound)
The separation membrane of the present embodiment is characterized in that a polymer compound having a carboxylate group in the molecule is contained in the entire separation membrane, that is, it is composed of a polymer compound having a carboxylate group in the molecule. The polymer compound exhibits an ion transporting property by having a carboxylate group in the molecule.

  Specifically, the polymer compound is preferably a polymer compound having a copolymer containing at least one selected from the group consisting of vinyl alcohol, vinyl acetal, and vinyl ester. Here, the copolymer containing at least one selected from the group consisting of vinyl alcohol, vinyl acetal, and vinyl ester is selected from vinyl alcohol monomer, vinyl acetal monomer, and vinyl ester monomer. Further, it means a copolymer having a structure derived from a monomer when at least one kind is addition-polymerized.

  In the present embodiment, when a vinyl alcohol-containing copolymer is used as the polymer compound, the saponification degree of the vinyl alcohol-containing copolymer is not particularly limited and is usually 50% or more, more preferably Is 80% or more, more preferably 95% or more. When the degree of saponification is low, it may be hydrolyzed by the alkali metal contained in the separation membrane and the stability may not be determined, which is not preferable.

  In addition, as an example of the vinyl ester that can be used in the present embodiment, vinyl acetate is typically used because of its market availability and high impurity treatment efficiency during production. Other than these, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl isovalerate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, etc. Aliphatic vinyl ester; aromatic vinyl ester such as vinyl benzoate and the like.

  Examples of the vinyl acetal of the present embodiment include vinyl formal, vinyl butyral, vinyl glyoxylic acid and the like, but vinyl glyoxylic acid which can be produced inexpensively and easily is preferable.

  The copolymerization form of the copolymer of the present embodiment is not particularly limited, and examples thereof include random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization and the like.

  The method for producing the copolymer of the present embodiment is also not particularly limited, and may be any polymerization initiation method such as anionic polymerization, cationic polymerization, and radical polymerization, and also as a method for producing a polymer, solution polymerization. Any method such as bulk polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization may be used.

  The polymer compound of the present embodiment may be a copolymer of the above-mentioned vinyl alcohol, vinyl acetal, and/or vinyl ester and another compound. In that case, the compound of the other party is not particularly limited as long as it does not impair the effects of the present invention, but α-olefins containing an alkyl group such as ethylene, 1-hexene, 1-dodecene, 2-acrylamido-2- Methylpropanesulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, acrylamide such as 6-acrylamidohexanoic acid, N-vinyl-ε-caprolactam, cyclic compounds such as 1-vinyl-2-pyrrolidone, 2-methyl-3- Examples include α-olefins containing alcohols such as buten-2-ol and 3-hydroxy-3-methyl-1-butene, and α-olefins containing silanes such as trimethoxyvinylsilane.

  The number average molecular weight of the copolymer of the present embodiment is preferably 5,000 to 250,000. When the number average molecular weight of the copolymer is less than 5,000, the mechanical strength of the separation membrane for a non-aqueous electrolyte battery may decrease. The number average molecular weight is more preferably 10,000 or more, further preferably 15,000 or more. On the other hand, when the number average molecular weight of the copolymer exceeds 250,000, the copolymer may cause polymer coagulation in the coating aqueous solution, or the viscosity stability of the coating aqueous solution may be deteriorated. The homogeneity and productivity of the battery separation membrane may be insufficient. The number average molecular weight is more preferably 200,000 or less, still more preferably 150,000 or less. The number average molecular weight of the copolymer in the present invention means a value measured by gel permeation chromatography (GPC) method using polyethylene oxide and polyethylene glycol as standard substances and an aqueous column as a column.

  The polymer compound contained in the separation membrane of the present embodiment is characterized by containing a carboxylate group in the molecule.

  In the polymer compound having a carboxylate group of the present embodiment, it is desirable that the melting point at which the physical properties of the separation membrane greatly change is 180° C. or higher. Although the separation membrane of the present embodiment does not have a shutdown function, since the separation membrane itself has heat resistance, the shape and physical properties do not change even at a cell internal temperature of 180° C. or higher, safety is high without short circuit, and heat resistance is high. Since a coating agent for imparting properties is not required, productivity can be improved. More preferably, it is desirable to use a polymer compound having a carboxylic acid group having a melting point of 200° C. or higher. The upper limit of the melting point is not particularly limited, but it is preferably 300° C. or lower from the viewpoints of flexibility and strength of the separation membrane and productivity for producing a polymer compound.

  In the present embodiment, the melting point is adjusted within the above range by adjusting, for example, the molecular weight, crystallinity, saponification degree, and neutralization degree of the copolymer contained in the polymer compound having a carboxylate group. However, the method for adjusting the melting point is not limited thereto.

  In the present embodiment, the method for measuring the melting point is not particularly limited, but it can be measured by, for example, the method described in Examples below.

  In the present embodiment, the polymer compound contains a carboxylic acid forming a carboxylic acid group. Examples of the carboxylic acid include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; unsaturated dicarboxylic acids such as fumaric acid, itaconic acid and maleic acid; and glyoxylic acid. A carboxylic acid is present in the polymer compound as a monomer unit. Among these, acrylic acid, methacrylic acid, maleic acid, and glyoxylic acid are particularly preferable from the viewpoints of availability, polysynthesis, and stability of the product. These carboxylic acids (monomers) may be used alone or in combination of two or more.

  In the polymer compound of the present embodiment, the content ratio of the copolymer and the carboxylic acid (the amount of the carboxylic acid with respect to all the monomer units constituting the copolymer (the total amount of the carboxylic acid group and the carboxylic acid)) Is preferably in the range of 100/1 to 1/100 in terms of molar ratio. It is more preferably 50/100 or less, still more preferably 80/100 or less. Further, it is more preferably 100/3 or more, and further preferably 100/8 or more. This is because the advantages of hydrophilicity, water solubility, and affinity for metals and ions as a high molecular weight polymer that dissolves in water can be obtained. If the amount of the carboxylic acid is too small, the ion transport property will be reduced, and if it is too large, the flexibility as a separation membrane will be lowered, and it will be easily broken, and the thermal and electrical stability will be lowered.

  In the polymer compound of the present embodiment, carboxylic acid is a neutralized product by reacting active hydrogen of carbonyl acid generated from carboxylic acid with a basic substance to form a salt. In the neutralized salt used in the present embodiment, it is preferable to use a basic substance containing a monovalent or divalent metal and/or ammonia as the basic substance from the viewpoint of the ion transport property of the separation membrane.

  Examples of the basic substance that can be used in the present embodiment include ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide, and other alkali metal hydroxides; sodium carbonate, potassium carbonate. Alkali metal carbonates such as calcium carbonate and magnesium carbonate; alkali metal acetates such as sodium acetate, potassium acetate and calcium acetate; and alkali metal phosphates such as trisodium phosphate. Among these, ammonia, lithium hydroxide, sodium hydroxide and potassium hydroxide are preferable. In particular, ammonia, lithium hydroxide, and calcium carbonate are preferably used as the binder for the lithium ion secondary battery. The basic substance containing a monovalent or divalent metal and/or ammonia may be used alone or in combination of two or more kinds. In addition, if it is within the range that does not adversely affect the battery performance, a basic substance containing a hydroxide of an alkali metal or an alkaline earth metal such as sodium hydroxide or calcium hydroxide is used in combination to obtain a neutralized product. You may prepare.

  The degree of neutralization is not particularly limited, but in consideration of the ion transportability of the separation membrane, it is usually preferably in the range of 0.1 to 1 mol, and more preferably 1 mol per mol of the carboxylic acid. Is preferably in the range of 0.3 to 1 mol and is neutralized. With such a degree of neutralization, the ion transportability is excellent and the resistance can be suppressed to a low level, so that it is expected to contribute to the improvement of the low temperature characteristics of the battery. In addition, the flexibility of the separation membrane can be maintained. That is, it is preferable that the amount of the carboxylate group is 100/0.1 to 1/100 in terms of molar ratio with respect to all the monomer units constituting the above-mentioned polymer compound (copolymer). It is more preferably 5/100 or less, still more preferably 8/100 or less. Further, it is more preferably 100/0.3 or more, and further preferably 100/0.5 or more.

  In the present embodiment, the neutralization degree of the carboxylic acid salt can be determined by a method such as titration with a base, infrared spectrum, or NMR spectrum. To measure the degree of neutralization easily and accurately, titration with a base is performed. Is preferably performed. The specific titration method is not particularly limited, but dissolved in water containing few impurities such as ion-exchanged water, lithium hydroxide, sodium hydroxide, with a basic substance such as potassium hydroxide, It can be carried out by performing neutralization. The indicator of the neutralization point is not particularly limited, but an indicator such as phenolphthalein which indicates the pH with a base can be used.

  The carboxylic acid group is introduced into the polymer compound of the present embodiment by, for example, a copolymer containing at least one selected from the group consisting of vinyl alcohol containing carboxylic acid, vinyl acetal, and vinyl ester, and the above-mentioned base. It can be carried out by reacting with a basic substance (a basic substance containing a monovalent or divalent metal and/or ammonia). This reaction can be carried out according to a conventional method, but a method of carrying out the reaction in the presence of water to obtain a neutralized product as an aqueous solution is convenient and preferable.

  Further, in the polymer compound of the present embodiment, the carboxylic acid modification amount is preferably about 1 to 35 mol%, more preferably about 5 to 20 mol%. When the amount of carboxylic acid modification is within such a range, the ion transportability is excellent and the resistance can be suppressed to a low level. In addition, the flexibility of the separation membrane can be maintained. The amount of carboxylic acid modification can be measured by using methods such as titration with a base, infrared spectrum, and NMR spectrum.

(Separation membrane for non-aqueous electrolyte battery)
The separation membrane for a non-aqueous electrolyte battery of the present embodiment is a membrane containing a polymer compound as a main component (comprising a polymer compound) as described above, and other components unless impairing the effects of the present invention. Although it may contain some or other additives, it is preferably a film made of the above-mentioned polymer compound. The separation membrane for a non-aqueous electrolyte battery of the present embodiment, the polymer compound as described above is preferably 70 mass% or more, more preferably 75 mass% with respect to the entire components constituting the separation membrane for a non-aqueous electrolyte battery. Above, more preferably 85 mass% or more is contained. As the above-mentioned additives, various additives such as antioxidants, ultraviolet absorbers, lubricants, anti-blocking agents, etc. may be added, if necessary, within a range that does not significantly impair the effects of the present invention (for example, 5% by mass or less). can do.

  Further, the separation membrane of the present embodiment is a porous membrane having pores through which ions pass in a non-aqueous charge battery. The average pore diameter is usually 0.01 to 5 μm, preferably 0.02 to 3 μm, and more preferably 0.05 to 1 μm. If the pore size is too small, the electrolyte permeability is poor, making it difficult for ions to be transported and increasing the resistance. On the other hand, if it is too large, the electrodes are likely to come into contact with each other, causing a short circuit. The average pore size can be measured by the method described in the examples. In the present embodiment, the average pore size is preferably in the above range on either side of the wide-mouthed surface of the porous membrane, and more preferably on either side of the wide-mouthed surface.

  Further, the separation membrane of the present embodiment has a porosity of usually 10 to 90% by weight, preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight. When the porosity is too low, the liquid permeability of the electrolytic solution is poor, it becomes difficult to transport ions, and the resistance increases. On the other hand, if the porosity is too high, the strength of the film itself is lowered and cracks are likely to occur, which causes a short circuit. The porosity can be measured by the method described in the examples.

  The film thickness is not particularly limited, but is usually 1 to 100 μm, preferably 3 to 80 μm, and more preferably 5 to 50 μm. If it is too thick, the electrolyte permeability will be poor, making it difficult for ions to be transported and increasing the resistance. On the other hand, if it is too thin, the strength of the film itself is reduced, and cracks are likely to occur, which causes a short circuit.

(Production method of separation membrane)
In the present embodiment, the method for producing the separation membrane containing the polymer compound having a carboxylate group is not particularly limited as long as the membrane can be formed, but for example, the following (1) to (5) It can be manufactured by such a process.
(1) A step of mixing an aqueous solution of a polymer compound having a carboxylate group with an inorganic powder, an organic material, and/or an additive.
(2) A step of forming a sheet-like film by applying the aqueous solution obtained in the step (1) to a substrate.
(3) A step of extracting and removing inorganic powder or organic matter from the sheet-like film obtained in the step (2).
(4) A step of rolling and drying the film obtained in the step (3), if necessary.
(5) A step of peeling the film obtained in the step (4) from the base material.

  In the above step (1), first, an aqueous solution (for example, a 10 wt% aqueous solution) containing the polymer basket of the present embodiment is prepared. The content of the inorganic powder, the organic substance, the additive and the like with respect to the polymer compound having a carboxylate group is preferably 10 to 90% by weight, more preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight. %. If the amount is too small, the ion transportability is lowered, resulting in a high resistance. If the amount is too large, the strength of the membrane itself is lowered, and cracking is likely to occur, which may not function as a separation membrane.

  The inorganic powder used for producing the separation membrane containing the polymer compound of the present embodiment is preferably an inorganic fine powder, and specifically, silica, mica, talc, titanium oxide, aluminum oxide, ceramics. , Barium sulfate, synthetic zeolite and the like, and these may be used alone or in combination of two or more. The size of the inorganic powder may be any as long as it has a particle diameter such that the average pore diameter of the pores in the separation membrane falls within the range described above.

  Further, as the organic substance used in the production of the separation membrane containing the polymer compound of the present embodiment, water-soluble and in organic solvents such as alcohols, halogenated hydrocarbons, aliphatic hydrocarbons, etc. As long as it is soluble, polyethylene glycol can be used without particular limitation, but polyethylene glycol is preferable from the viewpoint of price and availability.

  In addition to the copolymer having the polymer compound of the present embodiment, the inorganic fine powder and the organic substance, the above-mentioned additives can be added together within a range that does not significantly impair the effects of the present invention.

  The base material used for coating is not particularly limited, and examples thereof include PET (polyethylene terephthalate), PTFE (polytetrafluoroethylene), PVC (polyvinyl chloride), PE (polyethylene) and the like. A release agent or the like may be used to improve the peeling property.

  In the step (2), for example, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, a brush coating is performed using the aqueous solution obtained in the above step (1). A sheet-like film is formed by a method such as a method. The coating amount may be such that the thickness of the obtained separation film is within the above range.

  In the step (3), the organic substance or inorganic powder added in the step (1) is extracted and removed from the sheet-like film obtained in the step (2). Specifically, a method of extracting and removing with a solvent in which the organic substance or the inorganic powder is dissolved and in which the polymer compound of the present embodiment is not dissolved may be mentioned. Such a solvent can be appropriately selected depending on the type of inorganic powder or organic substance, and examples thereof include alcohols, halogenated hydrocarbons, aliphatic hydrocarbons and the like.

  In the step (4), the sheet-like film after extraction and removal obtained in the above step (3) may be subjected to rolling or drying/removal of solvent/solvent, if necessary. The method for drying the solvent (water) is not particularly limited, and examples thereof include aeration drying with warm air, hot air, and low humidity air; vacuum drying; irradiation with infrared rays, far infrared rays, electron beams, and the like. The drying condition may be adjusted so that the solvent can be removed as quickly as possible within a speed range where the film is not cracked due to stress concentration. Further, the dried film may be rolled in order to improve the smoothness of the surface. Examples of the rolling method include methods such as die pressing and roll pressing.

  In the step (5), the film is peeled off from the base material. Either step (5) or step (4) may be performed first.

(Non-aqueous electrolyte battery)
The non-aqueous electrolyte battery of the present embodiment is characterized by including the above-mentioned separation membrane.

  Examples of the non-aqueous electrolyte battery include a lithium-ion battery, a sodium-ion battery, a lithium-sulfur battery, and an all-solid-state battery.

  The non-aqueous electrolyte battery usually contains a negative electrode, a positive electrode, and an electrolytic solution in addition to the above-mentioned separation membrane.

  As the negative electrode, a negative electrode usually used for non-aqueous electrolyte batteries such as lithium ion secondary batteries is used without particular limitation. For example, graphite, hard carbon, Si-based oxide, or the like is used as the negative electrode active material. In addition, the negative electrode active material, a conductive auxiliary agent shown above, and a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl call, etc., a boiling point of 100 at a normal pressure and water. The negative electrode slurry prepared by mixing with a solvent or the like at a temperature of not lower than 300° C. and not higher than 300° C. can be applied to a negative electrode current collector such as a copper foil and the solvent can be dried to form a negative electrode.

As the positive electrode, a positive electrode normally used for non-aqueous electrolyte batteries such as lithium ion secondary batteries is used without particular limitation. For example, as the positive electrode active _material, TiS 2, TiS _3, amorphous _{MoS 3, Cu 2 V 2 O} 3, amorphous _{V 2 O-P 2 O 5} , MoO 3, V 2 O 5, V 6 O A transition metal oxide such as ₁₃ and a lithium-containing composite metal oxide such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ and LiMn ₂ O ₄ are used. In addition, the positive electrode active material, a conductive auxiliary agent shown above, and a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl call, etc., a boiling point of 100 at water or the above atmospheric pressure. The positive electrode slurry prepared by mixing with a solvent having a temperature of not lower than 300° C. and not higher than 300° C. can be applied to a positive electrode current collector such as aluminum and the solvent can be dried to obtain a positive electrode.

Further, for the non-aqueous electrolyte battery of this embodiment, an electrolytic solution obtained by dissolving an electrolyte in a solvent can be used. The electrolytic solution may be liquid or gel as long as it is used for a non-aqueous electrolyte battery such as an ordinary lithium ion secondary battery, and exhibits a function as a battery depending on the types of the negative electrode active material and the positive electrode active material. What to do may be appropriately selected. Specific electrolytes, for example, also known lithium salt is any conventionally _{available, LiClO 4, LiBF 6, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10 _{, LiAlCl 4, LiCl, LiBr,} LiB (C 2 H 5) 4, CF 3 SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3, LiC 4 F 9 SO 3, Li (CF 3 SO 2) 2 N , Lower aliphatic lithium carboxylate, and the like.

  The solvent (electrolytic solution solvent) that dissolves such an electrolyte is not particularly limited. Specific examples include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate and diethyl carbonate; lactones such as γ-butyl lactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane. , Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane, 4-methyl-1,3-dioxolane; nitrogen-containing compounds such as acetonitrile and nitromethane; formic acid Organic acid esters such as methyl, methyl acetate, ethyl acetate, butyl acetate, methyl propionate and ethyl propionate; inorganic acid esters such as triethyl phosphate, dimethyl carbonate and diethyl carbonate; diglymes; triglymes; sulfolanes; Examples thereof include oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propanesultone, 1,4-butanesultone, and naphthalsultone. These can be used alone or in combination of two or more. When a gel electrolyte is used, a nitrile polymer, an acrylic polymer, a fluorine polymer, an alkylene oxide polymer or the like can be added as a gelling agent.

  In particular, by using a polymer compound having a copolymer containing vinyl alcohol, vinyl acetal and/or vinyl ester, which is the same material as the separation membrane of the present embodiment, as a binder used for the negative electrode or the positive electrode, the separation can be performed. It is more preferable to use the same kind of material as the binder as the binder, because productivity improvement is expected by preventing electrode displacement from the membrane and preventing the active material from falling off.

  The method for manufacturing the non-aqueous electrolyte battery of the present embodiment is not particularly limited, but the following manufacturing method is exemplified. That is, the negative electrode and the positive electrode are overlapped with each other via the separating film of the invention, and are wound or folded according to the shape of the battery, put into a battery container, and the electrolytic solution is injected and sealed. The shape of the battery may be any of known coin type, button type, sheet type, cylindrical type, square type, flat type and the like.

  The nonaqueous electrolyte battery of the present embodiment is a battery that has both improved heat resistance (safety) and improved battery characteristics, and is useful for various applications. For example, it is very useful as a battery used for a mobile terminal that requires miniaturization, thinning, weight reduction, and high performance.

  The present specification discloses various aspects of the techniques as described above, and the main techniques thereof are summarized below.

  That is, the battery separation membrane according to one aspect of the present invention is characterized by containing a polymer compound having a carboxylate group in the molecule.

  It is considered that such a structure can provide a separation membrane for a non-aqueous electrolyte battery having an ion transport property and can improve the battery characteristics.

  In the separation membrane for a non-aqueous electrolyte battery, it is preferable that the polymer compound has a copolymer containing at least one selected from the group consisting of vinyl alcohol, vinyl acetal, and vinyl ester.

  In the separation membrane for non-aqueous electrolyte battery, the separation membrane for non-aqueous electrolyte battery is preferably a porous membrane, and the porosity of the separation membrane for non-aqueous electrolyte battery is 10% or more. Is preferred. Therefore, it is considered that the liquid permeability of the electrolytic solution in the separation membrane is improved, the ions are easily transported, and the resistance can be suppressed.

  A non-aqueous electrolyte battery according to still another aspect of the present invention is characterized by including the separation membrane for a non-aqueous electrolyte battery. With such a configuration, it is possible to provide a non-aqueous electrolyte battery that is safe, has a long life, and has excellent battery characteristics.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

(Example 1)
A reactor equipped with a stirrer, a reflux condenser, an argon inlet, and an initiator addition port was charged with 640 g of vinyl acetate, 240.4 g of methanol and 0.88 g of acrylic acid, and nitrogen was bubbled through the system for 30 minutes while bubbling nitrogen. Replaced. Separately from this, a methanol solution of acrylic acid (concentration 20% by weight) was prepared as a comonomer sequential addition solution (hereinafter referred to as a delay solution), and argon was bubbled for 30 minutes. The temperature of the reactor was started to rise, and when the internal temperature reached 60° C., 0.15 g of 2,2′-azobisisobutyronitrile was added to start polymerization. While the polymerization reaction was in progress, the prepared delay solution was dropped into the system so that the monomer composition (molar ratio of vinyl acetate and acrylic acid) in the polymerization solution became constant. After polymerization was carried out at 60° C. for 210 minutes, it was cooled to stop the polymerization. Subsequently, unreacted monomers were removed while adding methanol occasionally at 30° C. under reduced pressure to obtain a methanol solution of polyvinyl acetate modified with acrylic acid. Then, 20.4 g of sodium hydroxide methanol solution (concentration 18.0% by weight) was added to 400 g of polyvinyl acetate methanol solution prepared by adding methanol to the polyvinyl acetate methanol solution to a concentration of 25% by weight. , 79.6 g of methanol were added and saponification was performed at 40°C. A gelled product was formed within a few minutes after the addition of the sodium hydroxide methanol solution, so this was ground with a grinder and left at 40° C. for 60 minutes to proceed with saponification. The obtained crushed gel was repeatedly washed with methanol, and then vacuum dried at 40° C. overnight to synthesize a target copolymer. The form of copolymerization was random polymerization. The carboxylic acid modification amount of the obtained copolymer was 5.0 mol %. Furthermore, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

<Measurement of melting point of polymer compound having carboxylate group>
Differential scanning calorimetry was performed using a thermal analyzer (Yamato Scientific Co., Ltd.). As a result of measurement at a measurement temperature range of 50°C to 1000°C and a heating rate of 10°C/min, the melting point was 220°C. The results are shown in Table 1 below.

<Preparation of coating liquid for separation membrane>
To 100 g of the 10 wt% aqueous solution of vinyl alcohol and acrylic acid copolymer obtained above, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer, and the mixture was heated and stirred at 80° C. for 2 hours. Then, the mixture was cooled to room temperature, polyethylene glycol (molecular weight 600, Wako Pure Chemical Industries, Ltd.) was added as solid content of 50% by weight, and the separation solution was adjusted to 10% by weight as solid content concentration of the aqueous solution (with vinyl alcohol). A coating solution of a neutralized salt of an ethylenically unsaturated carboxylic acid copolymer) was prepared.

<Preparation of separation membrane>
Using the fluororesin film (manufactured by Esco Co., Ltd.) as a base material and using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.), the separation membrane coating solution prepared above was applied thereon. Before drying, the substrate was immersed in isopropanol (IPA) to extract polyethylene glycol. The separation membrane dried at room temperature was peeled from the substrate, and then vacuum dried at room temperature to be used as the separation membrane. The thickness of the obtained separation membrane was 31 μm.

  The porosity and pore size of the obtained separation membrane were determined by the following methods, and the results are shown in Table 1.

<Calculation of porosity>
The porosity of the porous film was calculated according to the following formula by measuring the thickness and mass of a sample punched to a predetermined size (φ17 mm).
Porosity={1-(theoretical volume of separator/apparent volume of separator)}×100
Theoretical volume of separator = (mass of separator) / (theoretical density)
Apparent volume of separator = (thickness) x (area of separator)
Here, the theoretical density usually means the specific gravity of the polymer.

<Pore size>
It was calculated by averaging the diameters of 100 openings observed in the scanning electron micrograph. The surface to be observed was the wide-mouthed surface on the side opposite to the surface in contact with the substrate during the production of the porous film.

<Preparation of negative electrode for battery>
The electrode slurry was prepared by using 96 parts by weight of artificial graphite (FSN-1, manufactured by Sugisugi, China) as the active material for the negative electrode, and an SBR emulsion aqueous solution (TRD 2001, manufactured by JSR Corporation, 48.3% by weight) as a binder. As a solid content, 2 parts by weight, CMC-Na (sodium carboxymethyl cellulose; serogen BSH-6, manufactured by Dai-ichi Kogyo Seiyaku Co., 10% by weight) as a thickener, 1 part by weight as a solid content, and a conduction aid (conducting conductivity). 1 part by weight of Super-P (manufactured by Timcal Co., Ltd.) as a solid component into a special container as an agent) and kneaded using a planetary stirrer (ARE-250, manufactured by Shinky Co., Ltd.) to prepare a slurry for electrode coating. Was produced. The composition ratio of the active material and the binder in the slurry was graphite powder:conduction aid:SBR:CMC-Na=96:1:2:1 (weight ratio) as a solid content.

<Preparation of negative electrode for battery>
The obtained slurry was applied onto a copper foil (CST8G, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) as a current collector by using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.), and then at room temperature (24.5° C.). ) And then subjected to rolling treatment using a roll press (manufactured by Hosen Co., Ltd.). Then, after punching out as a battery electrode (φ14 mm), a coin battery electrode was produced by secondary drying under reduced pressure conditions at 140° C. for 3 hours.

<Production of battery>
The battery coated electrode obtained above was transferred to a glove box (manufactured by Miwa Seisakusho) under an argon gas atmosphere. A metal lithium foil (thickness 0.2 mm, φ16 mm) was used for the positive electrode. Also, using the separation membrane obtained above as a separator, the electrolyte solution was obtained by adding vinylene carbonate (VC) to ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of lithium hexafluorophosphate (LiPF6). A coin battery (2032 type) was prepared by injecting using a mixed solvent system (1M-LiPF6, EC/EMC=3/7 vol%, VC2 wt%).

<Resistance measurement>
Using the coin battery produced above, AC impedance measurement was performed using an impedance measuring device (potentiometer/galvanostat (SI1287, Solartron) and frequency response analyzer (FRA, Solartron)). The coin battery was placed in a thermostat at 25° C. and −20° C., and the impedance spectrum of the test battery was measured by the AC impedance method at a frequency of 0.01 to 106 Hz and a voltage amplitude of 10 mV. A diagram that includes arc-shaped parts on the complex plane (Cole-Cole plot) defined by the resistive component axis (Z axis, real number axis) and capacitive component axis (Z axis, imaginary number axis). The diameter of the arcuate part when expressed as the value of the interface resistance (Rin) with the separation membrane and the resistance component axis (Z axis, real number axis) when the capacitive component axis (Z axis, imaginary axis) is 0 Was calculated as the solution resistance (Rsol). The results are shown in Table 1.

(Example 2)
A reactor equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, and an initiator addition port was charged with 370 g of water and 100 g of commercially available polyvinyl alcohol (M115 manufactured by Kuraray Co., Ltd.) and heated at 95° C. with stirring. After dissolving the polyvinyl alcohol, it was cooled to room temperature. 0.5N (N) sulfuric acid was added to the aqueous solution to adjust the pH to 3.0. After adding 9.9 g of acrylic acid to the solution under stirring, the solution was heated to 70° C. while bubbling nitrogen into the aqueous solution, and nitrogen was replaced by bubbling nitrogen at 70° C. for 30 minutes. After purging with nitrogen, 80.7 g of an aqueous potassium persulfate solution (concentration 2.5% by weight) was added dropwise to the aqueous solution over 1.5 hours. After the whole amount was added, the temperature was raised to 75° C., the mixture was stirred for another hour, and then cooled to room temperature. The film was frozen in liquid nitrogen, crushed using a centrifugal crusher, and vacuum dried at 40° C. overnight to obtain a target copolymer. The form of copolymerization was block polymerization. The amount of the ethylenically unsaturated carboxylic acid modified in the obtained copolymer was 6.0 mol %. Furthermore, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Example 3)
100 g of commercially available polyvinyl alcohol (manufactured by Kuraray Co., Ltd., 28-98s) was irradiated with an electron beam (30 kGy). Next, 33.4 g of acrylic acid and 466.6 g of methanol were charged into a reactor equipped with a stirrer, a reflux condenser, a nitrogen inlet pipe, and a particle addition port, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. .. 100 g of polyvinyl alcohol irradiated with an electron beam was added thereto, and the mixture was stirred and heated and refluxed for 300 minutes while the particles were dispersed in the solution to carry out graft polymerization. Then, the particles were collected by filtration and vacuum dried at 40° C. overnight to obtain a target copolymer. The form of copolymerization was graft polymerization. The amount of ethylenically unsaturated carboxylic acid modification of the obtained copolymer was 7.3 mol %. Further, lithium hydroxide was added in an amount of 0.5 equivalent to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Example 4)
A target copolymer was synthesized in the same manner as in Example 2 except that 20 g of acrylic acid and 150 g of an aqueous potassium persulfate solution (concentration 2.5% by weight) were added. The form of copolymerization was block polymerization. The carboxylic acid modification amount of the obtained copolymer was 12.0 mol %. Furthermore, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 31 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Example 5)
Except that 0.2 equivalent of lithium hydroxide and 0.3 equivalent of sodium hydroxide were added to 100 g of a 10% by weight aqueous solution of vinyl alcohol and acrylic acid copolymer prepared in Example 4 with respect to carboxylic acid units in the polymer. A neutralized salt was prepared in the same manner as in Example 4.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 29 μm. Further, the porosity and the pore size were determined by the same method as in Example 1, and the resistance was measured. The results are shown in Table 1 below.

(Example 6)
A neutralized salt of the copolymer was prepared in the same manner as in Example 4 except that 1.0 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Example 7)
A neutralized salt of the copolymer was prepared in the same manner as in Example 4 except that 0.2 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, the porosity and the pore size were determined by the same method as in Example 1, and the resistance was measured. The results are shown in Table 1 below.

(Example 8)
100 g of commercially available polyvinyl alcohol (Kuraray Co., Ltd., Elvanol 71-30) was irradiated with an electron beam (30 kGy). Next, 25 g of methacrylic acid and 475 g of methanol were charged into a reactor equipped with a stirrer, a reflux cooling tube, a nitrogen introduction tube, and a particle addition port, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. 100 g of polyvinyl alcohol irradiated with an electron beam was added thereto, and the mixture was stirred and heated and refluxed for 300 minutes while the particles were dispersed in the solution to carry out graft polymerization. Then, the particles were collected by filtration and vacuum dried at 40° C. overnight to obtain a target copolymer. The form of copolymerization was graft polymerization. The amount of the ethylenically unsaturated carboxylic acid modified in the obtained copolymer was 7.0 mol %. Furthermore, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 29 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Example 9)
A target copolymer was synthesized in the same manner as in Example 5 except that 100 g of methacrylic acid and 400 g of methanol were added. The form of copolymerization was graft polymerization. The ethylenically unsaturated carboxylic acid modification amount of the obtained copolymer was 34.0 mol %. Furthermore, 0.5 equivalent of lithium hydroxide was added to the carboxylic acid unit in the polymer to prepare a neutralized salt of the copolymer.

  The melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 29 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Comparative Example 1)
A copolymer was obtained in the same manner as in Example 1 except that lithium hydroxide was not added. The form of copolymerization was random polymerization. Then, the melting point was measured by the same method as in Example 1. Further, a separation membrane coating solution having a solid content concentration of 10% by weight was prepared in the same manner as in Example 1, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, the porosity and the pore size were determined by the same method as in Example 1, and the resistance was measured. The results are shown in Table 1 below.

(Comparative example 2)
A copolymer was obtained in the same manner as in Example 2 except that lithium hydroxide was not added. Then, the melting point was measured by the same method as in Example 1. After that, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared in the same manner as in Example 1, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. The results are shown in Table 1 below.

(Comparative example 3)
A copolymer was obtained in the same manner as in Example 3 except that lithium hydroxide was not added. The form of copolymerization was block polymerization. Then, the melting point was measured by the same method as in Example 1. After that, a separation membrane coating solution having a solid content concentration of the aqueous solution of 10% by weight was prepared in the same manner as in Example 1, and a separation membrane and a battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 29 μm. Further, the porosity and the pore size were determined by the same method as in Example 1, and the resistance was measured. The results are shown in Table 1 below.

(Comparative example 4)
As in Example 1, except that commercially available polyvinyl alcohol (manufactured by Kuraray Co., Ltd., 28-98s, saponification degree: 98, block polymerization) was used as the polymer compound, the solid content concentration of the aqueous solution was 10% by weight. The separation membrane coating solution was prepared and the separation membrane and the battery were prepared in the same manner as in Example 1. The thickness of the obtained separation membrane was 30 μm. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. Further, the melting point of polyvinyl alcohol was measured in the same manner as in Example 1. The results are shown in Table 1 below.

(Comparative example 5)
A battery was manufactured in the same manner as in Example 1 except that a commercially available polypropylene oxide separator (Celgard #2400, film thickness: 25 μm, manufactured by Polypore) was used as the separation membrane. Further, by the same method as in Example 1, the porosity and the pore size were obtained and the resistance was measured. Further, the melting point of Celgard was measured by the same method as in Example 1. The results are shown in Table 1 below.

(Discussion)
In Examples 1 to 9, it was demonstrated that the polymer compound forming the separation membrane has a carboxylate group, so that the resistance can be reduced even at a low temperature. On the other hand, it is clear that the polymers containing a carboxylic acid but not containing a salt (Comparative Examples 1 to 3) and the polymer containing a carboxylic acid itself (Comparative Example 4) have high resistance even at room temperature or at a low temperature. became. Furthermore, even when compared with a separator (Comparative Example 5) which is one of the general-purpose products, it was revealed that the case where the separation membrane of the present invention was used exhibited excellent resistance characteristics. It is presumed that this is because the polymer compound contained a carboxylate group, so that ion transport was smoothly performed in the separation membrane. Further, it was shown that the compounds shown in Examples were superior in heat resistance to the general-purpose separator shown in Comparative Example 5.

  This application is based on Japanese Patent Application No. 2017-142571 filed on July 24, 2017, the content of which is included in the present application.

  In order to represent the present invention, the present invention has been appropriately and sufficiently described through the embodiments with reference to the specific examples and the like, but those skilled in the art can easily modify and/or improve the embodiments. It should be recognized that this is possible. Therefore, unless a modification or improvement carried out by a person skilled in the art is at a level that deviates from the scope of rights of the claims set forth in the claims, the modification or the improvement is covered by the scope of rights of the claim. Is understood to be included in.

  INDUSTRIAL APPLICABILITY The present invention has wide industrial applicability in the technical field of non-aqueous electrolyte batteries such as lithium ion secondary batteries.

Claims (5)

  A separation membrane for a non-aqueous electrolyte battery, which is composed of a polymer compound having a carboxylate group in the molecule.   The separation for a non-aqueous electrolyte battery according to claim 1, wherein the polymer compound has a copolymer containing at least one selected from the group consisting of vinyl alcohol, vinyl acetal, and vinyl ester. film.   The separation membrane for a non-aqueous electrolyte battery according to claim 1, wherein the separation membrane for a non-aqueous electrolyte battery is a porous membrane.   The separation membrane for a non-aqueous electrolyte battery according to claim 3, wherein the porosity of the separation membrane for the non-aqueous electrolyte battery is 10% or more.   A non-aqueous electrolyte battery comprising the separation membrane for a non-aqueous electrolyte battery according to claim 1.