WO2019021810A1

WO2019021810A1 - Separation membrane for nonaqueous electrolyte batteries, and nonaqueous electrolyte battery using same

Info

Publication number: WO2019021810A1
Application number: PCT/JP2018/026024
Authority: WO
Inventors: 有紀太田; 岩崎　秀治
Original assignee: 株式会社クラレ
Priority date: 2017-07-24
Filing date: 2018-07-10
Publication date: 2019-01-31
Also published as: TW201909466A; CN111052445A; JPWO2019021810A1; KR20200019962A

Abstract

One aspect of the present invention relates to: a separation membrane for nonaqueous electrolyte batteries, which is characterized by containing a polymer compound that has a carboxylate salt group in each molecule; and a nonaqueous electrolyte battery which uses this separation membrane for nonaqueous electrolyte batteries.

Description

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

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

In recent years, the spread of mobile terminals such as mobile phones, laptop computers, pad-type information terminals and the like has been remarkable. A lithium ion secondary battery is often used for the secondary battery used for the power supply of these portable terminals. As portable terminals are required to have more comfortable portability, miniaturization, thinning, weight reduction, and high performance have rapidly progressed, and they are used in various places. This trend continues, and batteries used in portable terminals are also required to be smaller, thinner, lighter and higher in performance.

Furthermore, the movement to use non-aqueous electrolyte batteries is also spreading to large-sized devices such as electric vehicles, hybrid vehicles, and electric vehicles. Therefore, performance such as high capacity and high current charge / discharge characteristics are required, but because it is a non-aqueous electrolyte battery, it has a high risk of smoke, ignition, rupture, etc. compared to water-based batteries. It is known and safety improvement is required.

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

Therefore, the risk of smoke and the like 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 the external protection circuit. Moreover, it is possible to suppress the temperature rise of the battery also by the shutdown function of the separator.

Heretofore, in general, for example, a porous film of a polyolefin resin has often been used as a non-aqueous electrolyte battery separation membrane. This porous film melts when the temperature inside the battery reaches around 120 ° C., and the holes are closed to block the flow of current or ions, thereby maintaining the safety (shutdown function). . However, when the temperature rises due to external heat or when a chemical reaction occurs inside the battery due to the temperature rise, the battery temperature will rise even after the shutdown function works, and the battery temperature may reach 150 ° C or more is there. In such a case, the porous film shrinks to cause an internal short circuit, which may cause ignition or the like.

To solve these problems, a coating layer highly filled with an inorganic filler is provided on a porous film of a polyolefin resin to cause abnormal heat generation, even when the shutdown temperature is exceeded and the temperature continues to rise. It has been reported that the short circuit of both poles can be prevented (for example, patent document 1).

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

In addition, from the viewpoint of safety, a solid polymer electrolyte has been proposed in which the form of uniform solid solution of the electrolyte in the polymer has been proposed (for example, Patent Document 2). Although the ion conductivity is lower than that of the liquid added electrolyte and improvement is in progress, there are problems in practical use.

As described above, it is difficult to produce a separation film having high safety, suppressing the increase in internal resistance due to the separator to improve battery characteristics such as battery capacity, in particular, to reduce resistance, and having high productivity. Met.

The present invention has been made in view of the above problems, and provides a separator for a non-aqueous electrolyte battery having high heat resistance and low resistance and excellent productivity, and an electric element (non-aqueous electrolyte battery) using the same. Intended to be provided.

JP 2007-280911 A Patent 4888366 gazette

MEANS TO SOLVE THE PROBLEM The present inventors found that the said objective will be achieved by using the separation membrane of the following structure, as a result of earnestly researching that the said subject should be solved, and this invention is repeated by repeating examination based on this knowledge. completed.

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

According to the present invention, it is possible to provide a separation membrane for a non-aqueous electrolyte battery that is safe and low in resistance, 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 non-aqueous electrolyte battery (hereinafter also referred to simply as separation membrane) separates the positive electrode and the negative electrode in the non-aqueous electrolyte battery, and allows the electrolyte to pass through or hold to separate the positive electrode and the negative electrode. It refers to a membrane having ion transportability that allows ions to pass between.

(Polymer compound)
The separation membrane of the present embodiment is characterized by including a polymer compound having a carboxylate group in the molecule throughout the separation membrane, ie, comprising a polymer compound having a carboxylate group in the molecule. The polymer compound exhibits ion transportability 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, a 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 It means a copolymer having a monomer-derived structure when addition polymerization of at least one of them is performed.

In the present embodiment, when a copolymer containing vinyl alcohol is used as the polymer compound, the degree of saponification of the copolymer containing vinyl alcohol is not particularly limited, and usually 50% or more, more preferably Is 80% or more, more preferably 95% or more. When the degree of saponification is low, the alkali metal contained in the separation membrane may cause hydrolysis 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 from the viewpoint of market availability and good impurity treatment efficiency at the time of production. In addition, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl pivalate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, etc. Aliphatic vinyl esters; aromatic vinyl esters such as vinyl benzoate and the like can be mentioned.

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

The copolymerization form of the copolymer of the present embodiment is not particularly limited, and random copolymerization, alternating copolymerization, block copolymerization, graft copolymerization and the like can be mentioned.

The method for producing the copolymer of the present embodiment is also not particularly limited, and any polymerization initiation method such as anionic polymerization, cationic polymerization, radical polymerization, etc. may be used, and as a method for producing a polymer, solution polymerization may be used. 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 vinyl alcohol, vinyl acetal, and / or vinyl ester as described above and other compounds. In that case, the compound of the other side is not particularly limited as long as the effect of the present invention is not impaired, but α-olefin containing an alkyl group such as ethylene, 1-hexene, 1-dodeken and the like, 2-acrylamido-2- Acrylamides such as methyl propane sulfonic acid, (3-acrylamidopropyl) trimethyl ammonium chloride, 6-acrylamido hexanoic acid, cyclic compounds such as N-vinyl-ε-caprolactam, 1-vinyl-2-pyrrolidone, etc., 2-methyl-3- Examples thereof include α-olefins including alcohols such as buten-2-ol and 3-hydroxy-3-methyl-1-butene, and α-olefins including silanes such as trimethoxyvinylsilane.

The 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 non-aqueous electrolyte batteries may be reduced. The number average molecular weight is more preferably 10,000 or more, and still more 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 aggregation of the polymer in the coating aqueous solution, or the viscosity stability of the coating aqueous solution may be reduced, and the non-aqueous electrolyte The uniformity and productivity of the battery separation membrane may be insufficient. The number average molecular weight is more preferably 200,000 or less, further 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) 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 in that it contains 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 largely change be 180 ° C. or higher. The separation membrane of this embodiment does not have a shutdown function, but since the separation membrane itself has heat resistance, the shape and physical properties do not change even at a cell temperature of 180 ° C. or higher, and safety is high without shorting. 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 is preferably 300 ° C. or less from the viewpoint of the flexibility and strength of the separation membrane and the productivity for producing a polymer compound.

In the embodiment, the melting point is adjusted to the above range, for example, by adjusting the molecular weight, the degree of crystallinity, the degree of saponification, and the degree of neutralization of the copolymer contained in the polymer compound having a carboxylic acid group. Although it is possible, the method of adjusting the melting point is not limited thereto.

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

In the present embodiment, the polymer compound contains a carboxylic acid that forms 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; glyoxylic acid etc. 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 preferable from the viewpoint of availability, heavy synthesis 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 (amount of carboxylic acid relative to all monomer units constituting the copolymer (total amount of carboxylic acid group and carboxylic acid)) Is preferably in the range of 100/1 to 1/100 in molar ratio. More preferably, it is 50/100 or less, more preferably 80/100 or less. Moreover, More preferably, it is 100/3 or more, More preferably, it is 100/8 or more. This is because the advantages of hydrophilicity, water solubility, affinity to metals and ions as a high molecular weight soluble in water can be obtained. When the amount of the carboxylic acid is too small, the ion transportability is reduced, and when it is too large, the flexibility as the separation membrane is reduced and not only it becomes easy to break but also the thermal and electrical stability is reduced.

In the polymer compound of the present embodiment, in the carboxylic acid, the active hydrogen of the carbonyl acid generated from the carboxylic acid is reacted with the basic substance to form a salt to become a neutralized product. In the neutralization 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 transportability of the separation membrane.

Examples of the basic substance that can be used in the present embodiment include hydroxides of alkali metals such as ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide and magnesium hydroxide; sodium carbonate, potassium carbonate And carbonates of alkali metals such as calcium carbonate and magnesium carbonate; acetates of alkali metals such as sodium acetate, potassium acetate and calcium acetate; and phosphates of alkali metals such as trisodium phosphate. Among these, ammonia, lithium hydroxide, sodium hydroxide and potassium hydroxide are preferable. In particular, as a binder for lithium ion secondary batteries, use of ammonia, lithium hydroxide and calcium carbonate is preferable. The basic substance containing a monovalent or divalent metal and / or ammonia may be used alone or in combination of two or more. Further, within the range not adversely affecting the battery performance, the neutralized product can be obtained by using in combination a basic substance containing an alkali metal such as sodium hydroxide or calcium hydroxide and an alkali earth metal hydroxide. It may be prepared.

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

In the present embodiment, the degree of neutralization of the carboxylate can be determined by a method such as titration with a base, infrared spectrum, NMR spectrum, etc. However, in order to measure the degree of neutralization conveniently and accurately, titration with a base is used. It is preferable to A specific titration method is not particularly limited, but it is dissolved in water with few impurities such as ion-exchanged water, and a basic substance such as lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. It can be implemented by neutralization. The indicator of the neutralization point is not particularly limited, but an indicator such as phenolphthalein which gives pH indication with a base can be used.

The introduction of a carboxylate group in the polymer compound of the present embodiment can be carried out, for example, by 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 sex 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 the method of carrying out the reaction in the presence of water to obtain the neutralized product as an aqueous solution is convenient and preferred.

In the polymer compound of the present embodiment, the carboxylic acid modification amount is preferably about 1 to 35 mol%, and more preferably about 5 to 20 mol%. If the amount of modification of the carboxylic acid is in this range, the ion transportability is excellent and the resistance can be suppressed to a low level, so that the contribution to the improvement of the low temperature characteristics of the battery is expected. In addition, the flexibility of the separation membrane can be maintained. The amount of carboxylic acid modification can be measured by using a method such as determination with a base, an infrared spectrum, or an NMR spectrum.

(Separation membrane for non-aqueous electrolyte batteries)
The separation membrane for a non-aqueous electrolyte battery of the present embodiment is a membrane (consisting of a polymer compound) containing the above-described polymer compound as a main component, and other components unless the effect of the present invention is impaired. Although it may contain some additives and the like, 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 is preferably 70% by mass or more, more preferably 75% by mass, of the polymer compound described above with respect to the entire components constituting the separation membrane for a non-aqueous electrolyte battery. The content is more preferably 85% by mass or more. In addition, as the above-mentioned additive, various additives such as an antioxidant, an ultraviolet absorber, a lubricant, an antiblocking agent and the like are added as needed within a range not significantly inhibiting the effect of the present invention (for example, 5% by mass or less) can do.

In addition, the separation membrane of the present embodiment is a porous membrane having pores through which ions can pass in a non-aqueous charged battery. The average pore size 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 will have poor liquid permeability, it will be difficult to transport ions, and resistance will be high. On the other hand, if the size is too large, the electrodes are likely to be in contact with each other, causing a short circuit. In addition, an average hole diameter can be measured by the method as described in an Example. In the present embodiment, it is preferable that the average pore diameter of any of the wide-mouth surface of the porous membrane be in the above range, and it is more preferable that any wide-mouth surface also satisfy the above range.

Furthermore, the porosity of the separation membrane of the present embodiment is usually 10 to 90% by weight, preferably 20 to 80% by weight, and particularly preferably 30 to 70% by weight. When the porosity is too low, the liquid permeability of the electrolytic solution is poor, and it becomes difficult to transport ions, resulting in high resistance. On the other hand, if the porosity is too high, the strength of the membrane itself is reduced, and cracking easily occurs, 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 will not pass well, it will be difficult to transport ions, and the resistance will be high. On the other hand, if the film is too thin, the strength of the film itself is reduced, cracking is likely to occur, and it causes short circuit.

(Manufacturing method of separation membrane)
In the present embodiment, the method for producing a separation membrane containing a polymer compound having a carboxylic acid group is not particularly limited as long as it can form a membrane, but, for example, the following (1) to (5) It can manufacture by such a process.
(1) A step of mixing an aqueous solution of a polymer compound having a carboxylic acid group with an inorganic powder, an organic substance, and / or an additive and the like.
(2) A step of applying the aqueous solution obtained in the step (1) to a substrate to form a sheet-like film.
(3) A step of extracting and removing inorganic powder and 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) as required.
(5) A step of peeling the film obtained in the step (4) from the substrate.

In the step (1), first, an aqueous solution (for example, a 10% by weight aqueous solution) containing the polymer residue of the present embodiment is prepared. The content of the inorganic powder, the organic substance, the additive and the like is preferably 10 to 90% by weight, more preferably 20 to 80% by weight, particularly preferably 30 to 70% by weight based on the polymer compound having a carboxylic acid group. %. If the amount is too small, the ion transportability is reduced, and the resistance is high. If the amount is too large, the strength of the membrane itself may be reduced, and the membrane may be easily cracked and 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, ceramic And barium sulfate, synthetic zeolites, etc., which may be used alone or in combination of two or more. The size of the inorganic powder may be any particle size as long as the average pore diameter of the pores in the separation membrane is in the above-mentioned range.

Moreover, as an organic substance used for producing the separation membrane containing the polymer compound of the present embodiment, it is soluble in water, and organic solvents such as alcohols, halogenated hydrocarbons, aliphatic hydrocarbons and the like are used. Even if it is soluble, it can be used without particular limitation, but from the viewpoints of price and availability, polyethylene glycol is preferable.

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

The substrate used for coating is not particularly limited, and PET (polyethylene terephthalate), PTFE (polytetrafluoroethylene), PVC (polyvinyl chloride), PE (polyethylene) and the like can be mentioned. In addition, a release agent may be used to improve the releasability.

In the step (2), using the aqueous solution obtained in the above-mentioned step (1), for example, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, an immersion method, brush coating A sheet-like membrane is formed by a method such as a method. As a coating amount, the quantity from which the film thickness of the separation membrane obtained becomes the above-mentioned range is mentioned.

In the step (3), the organic substance or the inorganic powder added in the above-mentioned step (1) is extracted and removed from the sheet-like film obtained in the above-mentioned step (2). Specifically, there is a method of extracting and removing using a solvent in which the organic substance or the inorganic powder is dissolved and the polymer compound of the present embodiment is not dissolved. The solvent can be appropriately selected depending on the kind of inorganic powder and 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-mentioned step (3) may be subjected to rolling, drying removal of the solvent and the solvent, and the like as necessary. The method for drying the solvent (water) is not particularly limited, and examples thereof include dry drying with warm air, hot air, low humidity air; vacuum drying; irradiation drying with infrared rays, far infrared rays, electron beams and the like. The drying conditions may be adjusted so that the solvent can be removed as quickly as possible within a speed range in which stress concentration does not cause the film to crack. Furthermore, in order to improve the surface smoothness, the dried film may be rolled. As a rolling method, methods such as a die press and a roll press may be mentioned.

(5) In the step, the membrane is peeled off from the substrate. Either of the steps (5) and (4) may be performed first.

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

As a non-aqueous electrolyte battery, a lithium ion battery, a sodium ion battery, a lithium sulfur battery, an all solid battery etc. are mentioned, for example.

The non-aqueous electrolyte battery generally includes, in addition to the above-described separation membrane, a negative electrode, a positive electrode, and an electrolytic solution.

As a negative electrode, the negative electrode normally used for nonaqueous electrolyte batteries, such as a lithium ion secondary battery, is used without a restriction | limiting especially. For example, graphite, hard carbon, Si-based oxide, etc. are used as the negative electrode active material. In addition, the negative electrode active material comprises a conductive auxiliary agent as described above, a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl coal, etc. The negative electrode slurry prepared by mixing in a solvent or the like at a temperature of 300 ° C. to 300 ° C. can be applied to a negative electrode current collector such as a copper foil, for example, and the solvent can be dried to form a negative electrode.

As the positive electrode, the positive electrode usually used in nonaqueous electrolyte batteries such as lithium ion secondary batteries is used without particular limitation. For example, as a 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 Transition metal oxides such as ₁₃ and lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , and LiMn ₂ O ₄ are used. In addition, the positive electrode active material comprises a conductive auxiliary agent as described above, a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl coal, etc. The slurry for the positive electrode prepared by mixing in a solvent or the like at a temperature of 300 ° C. to 300 ° C. can be applied to a positive electrode current collector such as aluminum, for example, and the solvent can be dried to form a positive electrode.

Moreover, the electrolyte which dissolved the electrolyte in the solvent can be used for the non-aqueous electrolyte battery of this embodiment. The electrolytic solution may be liquid or gel as long as it is used for a non-aqueous electrolyte battery such as a normal lithium ion secondary battery, and exhibits the function as a battery depending on the type of negative electrode active material and positive electrode active material What should be selected may be selected appropriately. 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 And lower aliphatic carboxylic acid lithium.

The solvent (electrolyte solution solvent) for dissolving such an electrolyte is not particularly limited. Specific examples thereof 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 and 2-methyltetrahydrofuran; Sulfoxides such as dimethyl sulfoxide; Oxolanes such as 1,3-dioxolane and 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 acids such as triethyl phosphate, dimethyl carbonate and diethyl carbonate Diglymes; triglymes; sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone, naphtha sultone, etc. Or it can be used in mixture of 2 or more types. When a gel electrolyte solution 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, using the polymer compound having a copolymer containing vinyl alcohol, vinyl acetal and / or vinyl ester, which is the same kind of material as the separation membrane of the present embodiment, as the binder used for the negative electrode or the positive electrode It is more preferable to use a material of the same type as the separation membrane as the binder, because productivity improvement is expected by preventing electrode position displacement with the membrane and removal of the active material.

Although there is no limitation in particular as a method to manufacture the nonaqueous electrolyte battery of this embodiment, For example, the following manufacturing method is illustrated. That is, the negative electrode and the positive electrode are stacked through the film separation of the invention, wound or folded according to the battery shape, and placed in a battery container, and an 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 non-aqueous electrolyte battery of the present embodiment is a battery having both heat resistance (safety) and improved battery characteristics, and is useful for various applications. For example, it is also very useful as a battery used for a portable terminal that is required to be smaller, thinner, lighter, and have higher performance.

Although the present specification discloses various aspects of the technology as described above, the main technologies are summarized below.

It is considered that such a configuration can provide a separation membrane for a non-aqueous electrolyte battery having ion transportability, and can improve battery characteristics.

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

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

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

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

Example 1
In a reactor equipped with a stirrer, reflux condenser, argon inlet, and initiator addition port, charge 640 g of vinyl acetate, 240.4 g of methanol and 0.88 g of acrylic acid, and boil nitrogen for 30 minutes while bubbling nitrogen. Replaced. Separately, a methanol solution of acrylic acid (concentration: 20% by weight) was prepared as a sequentially added solution of comonomer (hereinafter referred to as a delay solution), and argon was bubbled for 30 minutes. The temperature rise of the reactor was started, and when the internal temperature reached 60 ° C., 0.15 g of 2,2′-azobisisobutyronitrile was added to initiate 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 to acrylic acid) in the polymerization solution became constant. After polymerization at 60 ° C. for 210 minutes, the polymerization was stopped by cooling. Subsequently, unreacted monomers were removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of acrylic acid-modified polyvinyl acetate. Next, 20.4 g of sodium hydroxide methanol solution (concentration 18.0 wt%) was added to 400 g of a methanol solution of polyvinyl acetate prepared by adding methanol to the methanol solution of polyvinyl acetate to make the concentration 25 wt%. Saponification was carried out at 40 ° C. by adding 79.6 g of methanol. A gelled product was formed several minutes after the addition of the sodium hydroxide methanol solution, and this was ground with a grinder and allowed to stand at 40 ° C. for 60 minutes to allow saponification to proceed. The pulverized gel thus obtained was repeatedly washed with methanol and then vacuum dried overnight at 40 ° C. to synthesize a target copolymer. The form of copolymerization was random polymerization. The amount of carboxylic acid modification of the obtained copolymer was 5.0 mol%. Furthermore, 0.5 equivalent of lithium hydroxide was added with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the said copolymer was performed.

<Measurement of melting point of polymer compound having carboxylic acid group>
Differential scanning calorimetry was performed using a thermal analyzer (manufactured by Yamato Scientific Co., Ltd.). As a result of measurement in a measurement temperature range of 50 ° C. to 1000 ° C. and a temperature rising 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 a 10 wt% aqueous solution of vinyl alcohol and acrylic acid copolymer obtained above was added 0.5 equivalent of lithium hydroxide with respect to the carboxylic acid unit in the polymer, and heated and stirred at 80 ° C. for 2 hours. After that, it was cooled to room temperature, and 50% by weight of polyethylene glycol (molecular weight 600, Wako Pure Chemical Industries, Ltd.) was added as solid content, and the separation membrane coating solution (vinyl alcohol and A coating solution of a neutralized salt of an ethylenically unsaturated carboxylic acid copolymer was prepared.

<Preparation of separation membrane>
The separation membrane coating solution prepared above was applied thereon using a fluorocarbon resin film (manufactured by Esco Inc.) as a base material and a bar coater (T101 manufactured by Matsuo Sangyo Co., Ltd.). Before drying, the substrate was immersed in isopropanol (IPA) to extract polyethylene glycol. The separation membrane dried at room temperature was peeled off from the substrate and then vacuum-dried at room temperature was used as a 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 method, and the results are shown in Table 1.

<Calculation of porosity>
The porosity of the porous membrane was calculated according to the following equation by measuring the thickness and mass of a sample punched to a predetermined size (φ 17 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>
The diameter was calculated by averaging the diameters of 100 openings observed in a scanning electron micrograph. In addition, the surface to observe observes the wide-mouthed surface on the opposite side to the surface which contacts a base material in the case of porous membrane preparation.

<Fabrication of negative electrode for battery>
The slurry for the electrode was prepared by using SBR-based emulsion aqueous solution (TRD 2001, manufactured by JSR Corporation, 48.3% by weight) as a binder to 96 parts by weight of artificial graphite (FSN-1, manufactured by Chubu Sugisugi) as an active material for negative electrode 2 parts by weight as solids, CMC-Na (sodium carboxymethylcellulose; Cellogen BSH-6, made by Dai-ichi Kogyo Seiyaku Co., 10% by weight) as thickener, 1 part by weight as solids, and conductive aid 1) parts by weight of Super-P (manufactured by Timcal Co., Ltd.) as solid content in an exclusive container as an agent), kneaded using a planetary stirrer (ARE-250, manufactured by Shinky Co., Ltd.), and slurry for electrode coating Was produced. The composition ratio of the active material to the binder in the slurry is, as a solid content, graphite powder: conductive auxiliary agent: SBR: CMC-Na = 96: 1: 2: 1 (weight ratio).

<Fabrication of negative electrode for battery>
The obtained slurry is coated on a copper foil (CST8G, manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.) of a current collector using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.), and room temperature (24.5 ° C.) After primary drying, rolling treatment was carried out using a roll press (manufactured by Takasen Co., Ltd.). Then, after punching out as a battery electrode (φ 14 mm), a coin battery electrode was manufactured by secondary drying at 140 ° C. for 3 hours under reduced pressure conditions.

<Fabrication of battery>
The coated electrode for a battery obtained above was transferred to a glove box (manufactured by Miwa Manufacturing Co., Ltd.) under an argon gas atmosphere. A metal lithium foil (thickness 0.2 mm, φ16 mm) was used as the positive electrode. In addition, using the separation membrane obtained above as a separator, an electrolytic solution was prepared by adding vinylene carbonate (VC) to ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of lithium hexafluorophosphate (LiPF6) Injection was performed using a mixed solvent system (1 M LiPF6, EC / EMC = 3/7 vol%, VC 2 wt%) to produce a coin battery (2032 type).

<Measurement of resistance>
Using the coin battery produced above, alternating current impedance measurement was carried out with an impedance measurement device (potentio / galvanostat (SI1287, manufactured by Solartron) and a frequency response analyzer (FRA, manufactured by Solartron). The coin cell was placed in a thermostat at 25 ° C. and -20 ° C., and the impedance spectrum of the test cell was measured by an AC impedance method at a frequency of 0.01-106 Hz and a voltage amplitude of 10 mV. A diagram including arcs on the complex plane (Cor-Cole plot) defined by the resistive component axis (Z axis, real axis) and the capacitive component axis (Z axis, imaginary axis) of the measured impedance spectrum The diameter of the arc-shaped part when represented by is the value of the resistance component axis (Z axis, real axis) when the interface resistance (Rin) with the separation membrane and the capacitive component axis (Z axis, imaginary axis) is 0 Was calculated as solution resistance (Rsol). The results are shown in Table 1.

(Example 2)
In a reactor equipped with a stirrer, a reflux condenser, a nitrogen introduction pipe, and an addition port for an initiator, 370 g of water and 100 g of a commercially available polyvinyl alcohol (made by Kuraray Co., Ltd., M115) are charged and heated at 95 ° C. while stirring. After dissolving the polyvinyl alcohol, it was cooled to room temperature. The pH was adjusted to 3.0 by adding 0.5 N (N) sulfuric acid to the aqueous solution. After 9.9 g of acrylic acid was added thereto with stirring, the solution was heated to 70 ° C. while bubbling nitrogen into the aqueous solution, and the mixture was further purged with nitrogen while bubbling nitrogen at 70 ° C. for 30 minutes. After nitrogen substitution, 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 addition of the whole amount, the temperature was raised to 75 ° C. and stirred for an additional hour, and then cooled to room temperature. The film was frozen with liquid nitrogen, pulverized using a centrifugal grinder, and further vacuum dried overnight at 40 ° C. to obtain a target copolymer. The form of copolymerization was block polymerization. The amount of modified ethylenically unsaturated carboxylic acid of the obtained copolymer was 6.0 mol%. Furthermore, 0.5 equivalent of lithium hydroxide was added with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the said copolymer was performed.

The melting point was measured in the same manner as in Example 1. In addition, a separation membrane coating solution was prepared in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. The results are shown in Table 1 below.

(Example 3)
100 g of commercially available polyvinyl alcohol (Kuraray Co., Ltd., 28-98 s) 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 introduction pipe and an addition port for particles, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. . Here, 100 g of polyvinyl alcohol irradiated with an electron beam was added, and stirring was carried out for 300 minutes in a state where the particles were dispersed in the solution, and reflux polymerization was carried out to carry out graft polymerization. Thereafter, the particles were collected by filtration, and the target copolymer was obtained by vacuum drying at 40 ° C. overnight. The form of copolymerization was graft polymerization. The amount of ethylenic unsaturated carboxylic acid modification of the obtained copolymer was 7.3 mol%. Furthermore, 0.5 equivalent of lithium hydroxide was added with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the said copolymer was performed.

(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 with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the said copolymer was performed.

The melting point was measured in the same manner as in Example 1. In addition, a separation membrane coating solution was prepared in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. 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 a carboxylic acid unit in the polymer to 100 g of a 10 wt% aqueous solution of vinyl alcohol and acrylic acid copolymer prepared in Example 4 Prepared the neutralization salt in the same manner as in Example 4.

The melting point was measured in the same manner as in Example 1. In addition, a separation membrane coating solution was prepared in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. 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 lithium hydroxide was added in an amount of 1.0 equivalent to the carboxylic acid unit in the polymer.

(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.

(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 condenser, a nitrogen introducing pipe, and an addition port of particles, and the system was purged with nitrogen for 30 minutes while bubbling nitrogen. Here, 100 g of polyvinyl alcohol irradiated with an electron beam was added, and stirring was carried out for 300 minutes in a state where the particles were dispersed in the solution, and reflux polymerization was carried out to carry out graft polymerization. Thereafter, the particles were collected by filtration, and the target copolymer was obtained by vacuum drying at 40 ° C. overnight. The form of copolymerization was graft polymerization. The amount of modification with ethylenic unsaturated carboxylic acid of the obtained copolymer was 7.0 mol%. Furthermore, 0.5 equivalent of lithium hydroxide was added with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the copolymer was performed.

(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 amount of ethylenic unsaturated carboxylic acid modification of the obtained copolymer was 34.0 mol%. Furthermore, 0.5 equivalent of lithium hydroxide was added with respect to the carboxylic acid unit in a polymer, and preparation of the neutralization salt of the copolymer was performed.

(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 in the same manner as in Example 1. Further, a separation membrane coating solution was prepared in the same manner as in Example 1 in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. 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 in the same manner as in Example 1. Thereafter, a separation membrane coating solution was prepared in the same manner as in Example 1 in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. 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 in the same manner as in Example 1. Thereafter, a separation membrane coating solution was prepared in the same manner as in Example 1 in which the solid content concentration of the aqueous solution was 10% by weight, 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. The results are shown in Table 1 below.

(Comparative example 4)
The solid content concentration of the aqueous solution is 10% by weight as in Example 1, except that commercially available polyvinyl alcohol (Kuraray Co., Ltd., 28-98s, saponification degree: 98, block polymerization) is used as the polymer compound. 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. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. 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 prepared in the same manner as in Example 1 except that a commercially available polypropylene-based separator (Celgard # 2400, film thickness: 25 μm, made by Polypore) was used as the separation membrane. Furthermore, the porosity and the pore diameter were determined by the same method as in Example 1, and the resistance measurement was performed. Further, the melting point of Celgard was measured in the same manner as in Example 1. The results are shown in Table 1 below.

(Discussion)
In Examples 1 to 9, it was shown that low resistance can be realized even at low temperature by the polymer compound constituting the separation membrane having a carboxylate group. On the other hand, it is apparent that the polymer containing carboxylic acid but containing no salt (Comparative Examples 1 to 3) and the polymer containing no carboxylic acid itself (Comparative Example 4) have high resistance at normal temperature and low temperature. became. Furthermore, even when compared with the separator (comparative example 5) which is one of the general-purpose products, it was revealed that the case of using the separation membrane of the present invention shows superior resistance characteristics. This is assumed to be due to the fact that ion transport was smoothly performed in the separation membrane when the polymer compound contained a carboxylate group. Furthermore, it was shown that the compounds shown in the examples were also superior in heat resistance to the general-purpose separator shown in Comparative Example 5.

This application is based on Japanese Patent Application No. 201-1422571 filed on Jul. 24, 2017, the contents of which are included in the present application.

Although the present invention has been described appropriately and sufficiently through the embodiments with reference to specific examples etc. in order to express the present invention, those skilled in the art can easily change and / or improve the aforementioned embodiments. It should be recognized that it is possible to Therefore, unless a change or improvement performed by a person skilled in the art is at a level that deviates from the scope of the claims of the claims, the change or the improvement is the scope of the claims of the claim It is interpreted as being included in

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

Claims

A separation membrane for a non-aqueous electrolyte battery, comprising a polymer compound having a carboxylic acid group in its molecule.
The non-aqueous electrolyte battery according to claim 1, wherein the polymer compound comprises a copolymer containing at least one selected from the group consisting of vinyl alcohol, vinyl acetal, and vinyl ester. film.
The separation membrane for non-aqueous electrolyte batteries according to claim 1 or 2, wherein the separation membrane for non-aqueous electrolyte batteries is a porous membrane.
The separation membrane for nonaqueous electrolyte batteries according to claim 3, wherein the porosity of the separation membrane for nonaqueous electrolyte batteries is 10% or more.
A non-aqueous electrolyte battery comprising the separation membrane for a non-aqueous electrolyte battery according to any one of claims 1 to 4.