WO2017022845A1

WO2017022845A1 - Resin composition for nonaqueous electrolyte battery separator, and separator for nonaqueous electrolyte battery and nonaqueous electrolyte battery using same

Info

Publication number: WO2017022845A1
Application number: PCT/JP2016/073048
Authority: WO
Inventors: 有紀太田; 俊充田中; 準治藤岡; 俊相趙; 岩崎　秀治
Original assignee: 株式会社クラレ
Priority date: 2015-08-06
Filing date: 2016-08-05
Publication date: 2017-02-09
Also published as: JPWO2017022845A1; TW201719953A; TWI602340B; JP6869888B2

Abstract

The present invention relates to: a resin composition for a nonaqueous electrolyte battery separator, the composition characterized in comprising a neutral salt of an α-olefin-maleic acid copolymer obtained by copolymerization of α-olefins and maleic acids, and in that the degree of neutralization of the carboxylic acid generated from the maleic acids in the copolymer is 0.3 to 1.0; a separator for a nonaqueous electrolyte battery; and a nonaqueous electrolyte battery.

Description

Non-aqueous electrolyte battery separator resin composition, and non-aqueous electrolyte battery separator and non-aqueous electrolyte battery using the same

The present invention relates to a resin composition for a non-aqueous electrolyte battery separator, and a separator for a non-aqueous electrolyte battery and a non-aqueous electrolyte battery using the same.

In recent years, mobile terminals such as mobile phones, notebook computers, pad-type information terminal devices have been widely used. Non-aqueous electrolyte batteries are frequently used as secondary batteries used as power sources for these portable terminals. Since portable terminals are required to have more comfortable portability, miniaturization, thinning, weight reduction, and high performance have rapidly progressed, and have come to be used in various places. This trend continues today, and batteries used in mobile terminals are further required to be smaller, thinner, lighter, and higher in performance.

Also, the movement to use non-aqueous electrolyte batteries is spreading to large equipment such as electric cars, hybrid cars, and electric cars. Therefore, performance such as high capacity and charge / discharge characteristics at a large current is required, but because it is a non-aqueous electrolyte battery, there is a high risk of smoke, ignition, rupture, etc. compared to an aqueous battery. There is a demand for improved safety.

A nonaqueous electrolyte battery has a positive electrode and a negative electrode installed via a separator, and a lithium salt such as LiPF ₆ , LiBF ₄ LiTFSI (lithium (bistrifluoromethylsulfonylimide)), LiFSI (lithium (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 fuming increases due to temperature rise due to external heat, overcharge, internal short circuit, external short circuit, etc. These can be prevented to some extent by an external protection circuit. In addition, the polyolefin resin porous film used as a non-aqueous electrolyte battery separator melts at around 120 ° C., and the pores are blocked to block the flow of current and ions, thereby suppressing the temperature rise of the battery. It is also possible. This is called a 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 further rises even if the shutdown function works, and when the battery temperature reaches 150 ° C or higher, The porous film contracted, causing an internal short circuit, which could cause ignition.

As described above, it is difficult to suppress the ignition of the battery by the shutdown function of the separator. In addition, with the increase in capacity of batteries, the increase in current during charging and discharging is also progressing, and in order to suppress the Joule heat generated at that time, it is also necessary to lower the electrical resistance value itself of the separator impregnated with the electrolytic solution It has become. Therefore, a metal oxide was used for the purpose of reducing the electrical resistance value while suppressing the ignition of the battery by increasing the heat shrinkage temperature more than the polyolefin resin porous film, thereby preventing the internal short circuit. Separators have been developed (for example, Patent Documents 1 and 2).

The formation of the heat-resistant layer in such a separator is performed by applying a pasted metal oxide on the surface of the separator, and as a thickener or dispersant when pasting the metal oxide, In general, carboxymethyl cellulose (hereinafter sometimes abbreviated as CMC) is often used as a binder (for example, Patent Document 3).

CMC has good adhesion to metal oxides and separators and has thermal stability of about 150 ° C. However, CMC has high electrical resistance and high electrical resistance during high rate and repeated charge / discharge. Short circuit easily occurs. As a result, there was a problem that heat was generated more than expected, and CMC was decomposed and it became difficult to function as a separator.

The present invention has been made in view of the above-mentioned problems, and has a low electrical resistance and a high heat resistance resin composition for a nonaqueous electrolyte battery separator, and a nonaqueous electrolyte battery separator and a nonaqueous solution using the same. An object is to provide an electrolyte battery.

JP-T-2001-527274 JP 2010-021033 A International Publication No. 2015/029944 Pamphlet

As a result of earnest research to solve the above-mentioned problems, the present inventors have used the non-aqueous electrolyte battery separator resin composition having the following constitution (hereinafter also simply referred to as a separator resin composition) to achieve the above object. The present invention has been completed by finding out to be achieved and further study based on this finding.

That is, the separator resin composition according to one aspect of the present invention includes a neutralized salt of an α-olefin-maleic acid copolymer obtained by copolymerizing an α-olefin and a maleic acid, and the copolymer. The degree of neutralization with respect to carboxylic acid produced from maleic acids in is from 0.3 to 1.0.

By using such a composition, it is considered that a separator having high heat resistance and capable of suppressing electric resistance can be provided.

In particular, in the resin composition for a separator, since the degree of neutralization of the α-olefin-maleic acid copolymer with respect to the carboxylic acid produced from the maleic acid is 0.3 to 1.0, the coating property is very good. There is an advantage that it is excellent.

Furthermore, since the water solubility of the composition is improved, the viscosity is increased, and the adhesion to the current collector foil and the binding property between molecules are increased. As a result, there is an advantage that it is not necessary to use a thickener or a dispersant.

A separator for a non-aqueous electrolyte battery according to still another aspect of the present invention includes a coating layer made of the above-described separator resin composition.

Further, a nonaqueous electrolyte battery according to still another aspect of the present invention is characterized by including the separator.

According to the present invention, it is possible to obtain a separator that is heat resistant, has few short circuits, and is excellent in productivity. Further, it can be used to improve battery characteristics of a nonaqueous electrolyte battery.

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

The resin composition for a separator of this embodiment includes a neutralized salt of an α-olefin-maleic acid copolymer obtained by copolymerizing an α-olefin and maleic acid, and has a neutralization degree in the copolymer. It is 0.3 to 1.0.

In this embodiment, an α-olefin-maleic acid copolymer obtained by copolymerizing an α-olefin and maleic acid is composed of a unit (A) based on α-olefin and a unit (B) based on maleic acid, The components (A) and (B) preferably satisfy (A) / (B) = 1/1 to 1/3 (molar ratio). Further, it is preferably a linear random copolymer having a weight average molecular weight of 10,000 to 500,000.

In the present embodiment, the unit (A) based on α-olefins is represented by the general formula —CH ² CR ¹ R ² — (wherein R ¹ and R ² may be the same or different from each other, and hydrogen, carbon Represents an alkyl group or an alkenyl group having a number of 1 to 10. The α-olefin used in this embodiment is a linear or branched olefin having a carbon-carbon unsaturated double bond at the α-position. In particular, olefins having 2 to 12 carbon atoms, particularly 2 to 8 carbon atoms are preferred. Representative examples that can be used include ethylene, propylene, n-butylene, isobutylene, n-pentene, isoprene, 2-methyl-1-butene, 3-methyl-1-butene, n-hexene, 2-methyl- 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-butene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethylbutadiene, 2,5 -Pentadiene, 1,4-hexadiene, 2,2,4-trimethyl-1-pentene and the like. Among these, isobutylene is particularly preferable from the viewpoints of availability, polysynthesis, and product stability. Here, the isobutylene includes a mixture containing isobutylene as a main component, for example, a BB fraction (C4 fraction). These olefins may be used alone or in combination of two or more.

In the present embodiment, maleic anhydride, maleic acid, maleic acid monoester (for example, methyl maleate, ethyl maleate, propyl maleate, phenyl maleate, etc.), maleic acid, as the unit (B) based on maleic acids Maleic anhydride derivatives such as diesters (eg dimethyl maleate, diethyl maleate, dipropyl maleate, diphenyl maleate etc.), maleic imides or N-substituted derivatives thereof (eg maleic imide, N-methylmaleimide, N N-substituted alkylmaleimides such as ethylmaleimide, N-propylmaleimide, Nn-butylmaleimide, Nt-butylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-ethyl Phenyl male N-substituted alkylphenylmaleimide such as imide, or N-substituted alkoxyphenylmaleimide such as N-methoxyphenylmaleimide and N-ethoxyphenylmaleimide), and further halides thereof (for example, N-chlorophenyl) Maleimide), citraconic anhydride, citraconic acid, citraconic acid monoester (eg, methyl citraconic acid, ethyl citraconic acid, propyl citraconic acid, phenyl citraconic acid, etc.), citraconic acid diester (eg, dimethyl citraconic acid, diethyl citraconic acid, citraconic acid) Citraconic anhydride derivatives such as dipropyl acid, diphenyl citraconic acid, etc.), citraconic acid imide or N-substituted derivatives thereof (for example, citraconic acid imide, 2-methyl-N-methylmaleimide, 2-methyl-N-ethylmale) N-substituted alkylmaleimides such as 2-methyl-N-propylmaleimide, 2-methyl-Nn-butylmaleimide, 2-methyl-Nt-butylmaleimide, 2-methyl-N-cyclohexylmaleimide 2-methyl-N-substituted alkylphenylmaleimide such as methyl-N-phenylmaleimide, 2-methyl-N-methylphenylmaleimide, 2-methyl-N-ethylphenylmaleimide, or 2-methyl-N- 2-methyl-N-substituted alkoxyphenylmaleimides such as methoxyphenylmaleimide and 2-methyl-N-ethoxyphenylmaleimide), and further halides thereof (eg 2-methyl-N-chlorophenylmaleimide) Is preferred. Among these, use of maleic anhydride is preferable from the viewpoint of availability, polymerization rate, and ease of molecular weight adjustment. These maleic acids may be used alone or in combination. Maleic acids are neutralized with alkali salts as described above, and the resulting carboxylic acid and carboxylic acid salt form a 1,2-dicarboxylic acid or salt form. This form has a function of capturing heavy metals eluted from the positive electrode.

The content ratio of each structural unit in the copolymer of the present embodiment is preferably such that (A) / (B) is in the range of 1/1 to 1/3 in terms of molar ratio. This is because the advantages of hydrophilicity, water solubility, and affinity for metals and ions as a high molecular weight substance that dissolves in water can be obtained. Particularly, it is desirable that the molar ratio of (A) / (B) is 1/1 or a value close thereto, in which case the unit based on α-olefin, that is, —CH ₂ CR ¹ R ² — A copolymer having a structure in which the units shown and units based on maleic acids are alternately repeated is obtained.

The mixing ratio of α-olefins and maleic acids to obtain the copolymer of the present embodiment varies depending on the composition of the target copolymer, but α-olefin of 1 to 3 times the number of moles of maleic acids. Use of olefin is effective for increasing the reaction rate of maleic acids.

The method for producing the copolymer of the present embodiment is not particularly limited, and for example, the copolymer can be obtained by radical polymerization. In this case, the polymerization catalyst used is an azo catalyst such as azobisisobutyronitrile, 1,1-azobiscyclohexane-1-carbonitrile, or an organic peroxide catalyst such as benzoyl peroxide or dicumyl peroxide. preferable. The amount of the polymerization catalyst used is required to be in the range of 0.1 to 5 mol%, preferably 0.5 to 3 mol% with respect to maleic acids. As a method for adding the polymerization catalyst and the monomer, they may be added all at the beginning of the polymerization, but it is desirable to add them sequentially as the polymerization proceeds.

In the method for producing a copolymer of this embodiment, the molecular weight can be appropriately adjusted mainly depending on the monomer concentration, the amount of catalyst used, and the polymerization temperature. For example, as a substance for reducing the molecular weight, a metal salt of Group I, II or III of the periodic table, a hydroxide, a halide of a Group IV metal, a general formula N≡, HN =, H ₂ N— or H It is also possible to adjust the molecular weight of the copolymer by adding an amine represented by ₄ N-, a nitrogen compound such as ammonium acetate or urea, or a mercaptan during the polymerization or during the polymerization. The polymerization temperature is preferably 40 ° C. to 150 ° C., more preferably 60 ° C. to 120 ° C. If the polymerization temperature is too high, the resulting copolymer tends to be in a block form, and the polymerization pressure may be significantly increased. The polymerization time is usually preferably about 1 to 24 hours, more preferably 2 to 10 hours. The amount of the polymerization solvent used is preferably adjusted so that the concentration of the obtained copolymer is 5 to 40% by weight, more preferably 10 to 30% by weight.

As described above, it is preferable that the copolymer of the present embodiment usually has a weight average molecular weight of 10,000 to 500,000. A more preferred weight average molecular weight is 15,000 to 450,000. When the weight average molecular weight of the copolymer of this embodiment is less than 10,000, the crystallinity is high and the binding strength between particles may be low. On the other hand, when it exceeds 500,000, the solubility in water or a solvent becomes small, and it may precipitate easily.

The weight average molecular weight of the copolymer of the present embodiment can be measured by, for example, a light scattering method or a viscosity method. When the intrinsic viscosity ([η]) in dimethylformamide is measured using a viscosity method, the copolymer of this embodiment preferably has an intrinsic viscosity in the range of 0.05 to 1.5. The copolymer of this embodiment is usually obtained in the form of a powder having a grain size of about 16 to 60 mesh.

In the present embodiment, the neutralized salt of the copolymer means that the active hydrogen of carbonyl acid generated from maleic acid reacts with a basic substance to form a salt to become a neutralized salt. Is preferred. In the neutralized salt of α-olefin-maleic acid copolymer used in the present embodiment, a basic substance containing a monovalent metal and / or ammonia is used as the basic substance from the viewpoint of coating properties. It is preferable.

In the present embodiment, the amount of the basic substance containing monovalent metal and / or ammonia is not particularly limited and is appropriately selected depending on the purpose of use and the like, but usually in the maleic acid copolymer. The amount is preferably 0.6 to 2.0 mol per mol of maleic acid unit. If it is such usage-amount, it will be possible to adjust the neutralization degree of the binder composition of this embodiment to a predetermined range. The amount of the basic substance containing a monovalent metal is preferably 0.8 to 1.8 moles per mole of maleic acid units in the maleic acid copolymer, so that there is little residual alkali and water solubility. The copolymer salt can be obtained.

The reaction of the α-olefin-maleic acid copolymer with a basic substance containing a monovalent metal and / or an amine such as ammonia can be carried out according to a conventional method, but is carried out in the presence of water, and α- A method for obtaining a neutralized salt of an olefin-maleic acid copolymer as an aqueous solution is simple and preferable.

Examples of basic substances containing monovalent metals that can be used in the present embodiment include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali metals such as sodium carbonate and potassium carbonate. Carbonates of alkali metals such as sodium acetate and potassium acetate; phosphates of alkali metals such as trisodium phosphate, and the like. Examples of amines such as ammonia include primary amines such as ammonia, methylamine, ethylamine, butylamine and octylamine, secondary amines such as dimethylamine, diethylamine and dibutylamine, tertiary amines such as trimethylamine, triethylamine and tributylamine, And polyamines such as ethylenediamine, butylenediamine, diethyleneimine, triethyleneimine, and polyethyleneimine. Among these, ammonia, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferable. In particular, it is preferable to use ammonia or lithium hydroxide as a binder for a lithium ion secondary battery. The basic substance containing monovalent metal and / or ammonia may be used alone or in combination of two or more. In addition, a neutralized salt of an α-olefin-maleic acid copolymer is used in combination with a basic substance containing an alkali metal hydroxide such as sodium hydroxide as long as the battery performance is not adversely affected. May be prepared.

Next, in the present embodiment, the degree of neutralization of the copolymer with respect to the carboxylic acid produced from maleic acid is 0.3 to 1.0. When the neutralization degree is less than 0.3, the solubility in water or a solvent becomes small, and it easily precipitates, making slurry coating difficult. On the other hand, when the degree of neutralization exceeds 1.0, the basic substance to be neutralized is excessively present in the slurry, which may become a resistance component. More preferably, the neutralization degree is in the range of 0.4 to 0.8. Thereby, the slurry composition which was excellent in applicability | paintability can be obtained.

In this embodiment, the degree of neutralization can be determined by a method such as titration with a base, an infrared spectrum, or an NMR spectrum. To measure the neutralization point simply and accurately, titration with a base can be performed. preferable. The specific titration method is not particularly limited, but it can be dissolved in water with little impurities such as ion-exchanged water, and a basic substance such as lithium hydroxide, sodium hydroxide, potassium hydroxide, It can be carried out by neutralization. The indicator for the neutralization point is not particularly limited, but an indicator such as phenolphthalein indicating pH with a base, and a PH meter can be used.

In this embodiment, the degree of neutralization in the copolymer may be adjusted, for example, by adjusting the degree of neutralization of the copolymer, or the degree of neutralization of an aqueous solution in which the copolymer is dissolved. May be adjusted directly. Specifically, for example, the degree of neutralization is adjusted by adjusting the addition amount of a basic substance (ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.) containing a monovalent metal as described above. Although it is possible to adjust to the said range, it is not limited to it. Specifically, as described above, the basic substance containing monovalent metal and / or ammonia is preferably used in an amount of preferably 0.6 to 2.0 mol per mol of maleic acid unit in the maleic acid copolymer. Can be adjusted to the above range. More preferably, the basic substance containing a monovalent metal and / or ammonia is added more reliably by adding 0.6 to 1.8 moles per mole of maleic acid units in the maleic acid copolymer. It is possible to adjust to the above range.

Next, in this embodiment, the ring-opening rate of the copolymer represents the hydrolysis rate of the site of maleic anhydride that is polymerized with α-olefins when maleic anhydride is used as the maleic acid. In the copolymer of the present embodiment, a preferable ring opening rate is 60 to 100%, more preferably 70% to 100%, and still more preferably 80 to 100%. When the ring-opening rate is too low, the structural freedom of the copolymer becomes small and the stretchability becomes poor, so that the force for adhering adjacent electrode material particles may be reduced, which is not preferable. Furthermore, there is a possibility that problems such as low affinity for water and poor solubility may occur. The ring-opening rate can be determined, for example, by measuring the hydrogen at the α-position of the maleic acid opened by 1H-NMR with reference to the hydrogen at the α-position of maleic anhydride. The ratio of the carbonyl group derived from the carbonyl group and the ring-opened maleic anhydride can also be determined by IR measurement.

Next, in this embodiment, the mass reduction rate of the α-olefin-maleic acid copolymer at 150 ° C. is preferably less than 4%, and the mass reduction rate is more preferably less than 2%. If the mass reduction rate is 4% or more, there is a possibility that the capacity is reduced by heat generated when charging and discharging are repeated.

In the present embodiment, the mass reduction rate can be adjusted to the above range by adjusting the degree of neutralization of the copolymer contained in the separator resin composition, for example. There is no limitation. Further, when the degree of neutralization is a certain level (neutralization degree = 1), it can be further adjusted by adjusting the molecular weight of the copolymer.

In the present embodiment, the mass reduction rate is not particularly limited, but can be measured by, for example, a method described in Examples described later.

The separator resin composition of the present embodiment may contain the α-olefin-maleic acid copolymer alone, and if necessary, a dispersing agent such as inorganic particles and surfactant. , Thickeners, wetting agents, antifoaming agents, and the like.

As the inorganic particles, any of synthetic products and natural products can be used without particular limitation. Examples of inorganic particles include alumina such as gibbsite, bayerite, boehmite and corundum, silica, titania, zirconia, magnesia, ceria, yttria, oxide ceramics such as zinc oxide and iron oxide, silicon nitride, titanium nitride and nitride. Nitride ceramics such as boron, silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, potassium titanate, talc, synthetic kaolinite, kaolin clay, kaolinite, flybontite, stevensite, dickite, nacrite , Halloysite, pyrophyllite, audnite, montmorillonite, beidellite, nontronite, bolcon score, saponite, hectorite, fluorine hectorite, soconite, swin Rudite, vermiculite, fluorine vermiculite, burcerin, sericite, amesite, keriaite, fraponite, brindriaite, bentonite, zeolite, biotite, phlogopite, fluorophlogopite, iron mica, yeastite, teniolite, siderophyllite Tetraferri iron mica, scale mica, fluorosilica mica, polyriccionite, muscovite, celadon stone, iron ceradon stone, iron alumino ceradon stone, alumino ceradon stone, Tobe mica, soda mica, clinnite, kinoshita, bite mica, Ananda stone, pearl mica, clinochlore, chamosite, penantite, nimite, bailicroa, dombasite, kukeasite, suedoite, hydrotalcite, calcium silicate, magnesium silicate, aluminum silicate, diatomaceous earth and ke Such as sand, and ceramics and glass fibers. These inorganic particles are used alone or in combination of two or more.

When the separator resin composition contains inorganic fine particles, the amount of the inorganic fine particles in the separator resin composition is usually 10 to 10,000 parts by weight with respect to 1 part by weight of the α-olefin-maleic acid copolymer. The amount is preferably 20 to 1000 parts by weight.

Examples of the dispersant such as a surfactant include anionic surfactants such as sulfate ester type, phosphate ester type, carboxylic acid type and sulfonic acid type, and cation type activities such as quaternary ammonium salt type and amidoamine type. Agents, amphoteric surfactants such as alkyl betaine type, amide betaine type and amine oxide type, nonionic surfactants such as ether type, fatty acid ester type and alkyl glucooxide, polyacrylic acid, polyacrylic acid salt, polysulfonic acid Various surfactants such as salts, polynaphthalene sulfonates, polyalkylene polyamine alkylene oxides, polyalkylene polyimine alkylene oxides, polyvinyl pyrrolidone, and cellulose type polymer surfactants can be used. For the purpose of preventing aggregation between fillers, these may be used alone or in combination of two or more. The dispersant is not limited to these as long as the same effects as those described above can be obtained.

When the separator resin composition contains a dispersant, the amount of the dispersant in the separator resin composition is usually 0.01 to 10 with respect to 100 parts by weight of the α-olefin-maleic acid copolymer. The amount is preferably parts by weight, more preferably 0.1 to 5 parts by weight.

Examples of the thickener include synthetic polymers such as polyethylene glycol, urethane-modified polyether, polyacrylic acid, polyvinyl alcohol, vinyl methyl ether-maleic anhydride copolymer, carbomethoxy cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, etc. Natural polysaccharides such as cellulose derivatives, xanthan gum, dieutan gum, welan gum, gellan gum, guar gum, carrageenan gum, and starches such as dextrin and pregelatinized starch. These may be used alone or in combination of two or more. The thickener is not limited to those as long as the same effects as those described above can be obtained.

When the separator resin composition contains a thickener, the amount of the thickener in the separator resin composition is usually 0.01 with respect to 100 parts by weight of the α-olefin-maleic acid copolymer. It is preferably ˜10 parts by weight, more preferably 0.1 to 5 parts by weight.

As the wetting agent, for example, an aliphatic polyether type nonionic surfactant, a polyoxyalkylene type nonionic surfactant, a modified silicone, a modified polyether, or a dimethylsiloxane polyoxyalkylene copolymer can be used. These are used singly or in combination of two or more. The wetting agent is not limited to these as long as the same effects as those described above can be obtained.

When the separator resin composition contains a wetting agent, the amount of the wetting agent in the separator resin composition is usually 0.01 to 10 with respect to 100 parts by weight of the α-olefin-maleic acid copolymer. The amount is preferably parts by weight, more preferably 0.1 to 5 parts by weight.

As the antifoaming agent, for example, various defoaming agents of mineral oil type, silicone type, acrylic type and polyether type can be used. These are used singly or in combination of two or more. The antifoaming agent is not limited to these as long as the same effects as those described above can be obtained.

When the separator resin composition contains an antifoaming agent, the amount of the antifoaming agent in the separator resin composition is usually 0.01 with respect to 100 parts by weight of the α-olefin-maleic acid copolymer. It is preferably ˜10 parts by weight, more preferably 0.1 to 5 parts by weight.

Examples of the solvent in the separator resin composition of the present embodiment include water, alcohols such as methanol, ethanol, propanol, and 2-propanol, cyclic ethers such as tetrahydrofuran and 1,4-dioxane, N, N-dimethyl, and the like. Examples include amides such as formamide and N, N-dimethylacetamide, cyclic amides such as N-methylpyrrolidone and N-ethylpyrrolidone, and sulfoxides such as dimethylsulfoxide. In these, use of water is preferable from a viewpoint of safety | security and solubility.

Moreover, when water is used as the solvent of the resin composition for a separator of the present embodiment, the organic solvents shown below may be used in combination within a range of preferably 20% by weight or less of the entire solvent. Such an organic solvent preferably has a boiling point at normal pressure of 100 ° C. or higher and 300 ° C. or lower, for example, hydrocarbons such as n-dodecane; alcohols such as 2-ethyl-1-hexanol and 1-nonanol. Esters such as γ-butyrolactone and methyl lactate; amides such as N-methylpyrrolidone, N, N-dimethylacetamide and dimethylformamide; and organic dispersion media such as sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane.

The amount of the solvent in the separator resin composition is usually preferably 40 to 150 parts by weight, more preferably 70 to 130 parts by weight with respect to 10 parts by weight of the α-olefin-maleic acid copolymer. is there. If the amount of the α-olefin-maleic acid copolymer is excessively small, the viscosity becomes low, the coating property is lowered, the separator substrate surface cannot be sufficiently covered, and a short circuit occurs. It may not develop. On the contrary, if the amount of α-olefin-maleic acid copolymer is excessively large, the viscosity becomes high and the coating property may be lowered, and the separator substrate surface may not be sufficiently coated, and the electrical resistance also increases. Therefore, the discharge capacity may be reduced.

Furthermore, the present invention includes a separator for a non-aqueous electrolyte battery provided with a coating layer made of the separator resin composition.

The separator for a nonaqueous electrolyte battery of the present embodiment can be obtained by coating the separator resin composition described above on a separator base material and forming a coating layer on the surface of the separator base. There is no particular limitation on the method for coating the separator resin composition on the separator substrate. For example, doctor blade method, dipping method, reverse roll method, direct roll method, gravure method, extrusion method, dipping method, brush coating method And the like.

In the present embodiment, there is no particular limitation on the amount of adhered layers coated with separator resin composition, preferably 1.0 ~ 30g / ^{m 2,} further 4.0 ~ 20g / ^{m 2} is more preferable. When the adhesion amount of the coating layer is less than 1.0 g / m ² , the separator base material surface cannot be sufficiently coated, the pore diameter becomes large, short circuit occurs, and good battery characteristics do not appear. There is. On the other hand, when the adhesion amount of the coated layer exceeds 30 g / m ² , it may be difficult to reduce the thickness of the separator.

The resin composition for a separator of the present embodiment can be used as an optional member as a separator base material that can prevent short-circuiting of electrodes in a nonaqueous electrolyte battery without hindering charging / discharging of the battery.

In this embodiment, as the separator substrate, for example, a porous film or a nonwoven fabric made of an organic material having fine pores can be used.

More specifically, as a constituent material of the separator substrate, polyethylene terephthalate, polybutylene terephthalate and derivatives thereof, aromatic polyester, polyester such as wholly aromatic polyester, polyolefin, acrylic, polyacetal, polycarbonate, aliphatic polyketone, Aromatic polyketone, aliphatic polyamide, aromatic polyamide, wholly aromatic polyamide, polyimide, polyamideimide, polyphenylene sulfide, polybenzimidazole, polyetheretherketone, polyethersulfone, poly (para-phenylenebenzobisthiazole), poly ( Para-phenylene-2,6-benzobisoxazole), polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyurethane and poly salts Such fibers and cellulosic fibers made of a resin such as vinyl and the like. The separator substrate of this embodiment may contain two or more of these constituent materials.

The thickness of the separator substrate is usually 0.5 μm or more, preferably 1 μm or more, and usually 40 μm or less, preferably 30 μm or less. Within this range, the resistance due to the separator substrate in the battery is reduced, and the workability during battery production is excellent.

In this embodiment, the method of drying after applying a solvent such as water contained in the resin composition for a separator to the separator base material is not particularly limited. For example, aeration drying with hot air, hot air, or low-humidity air; ; Irradiation drying of infrared rays, far infrared rays, electron beams, and the like. The drying conditions are as fast as possible while the layer covered with the separator resin composition cracks due to stress concentration or the layer covered with the separator resin composition does not peel from the separator. It is good to adjust as possible.

In the non-aqueous electrolyte battery separator of the present embodiment, the basis weight of the separator is preferably from 10.0 ~ 50.0g / ^{m 2,} more preferably 15.0 ~ 40.0g / ^{m 2.} The thickness of the separator is preferably 10.0 to 50.0 μm, and more preferably 15.0 to 40.0 μm. Preferably 0.4 ~ 1.2g / cm ³ as the density of the separator, more preferably 0.6 ~ 1.0g / cm ^3.

In this embodiment, after coating and drying the resin composition, the separator coating layer may be smoothed by calendaring for the purpose of controlling the flattening and thickness of the coating layer surface.

Furthermore, the present invention also includes a nonaqueous electrolyte battery including the separator, the negative electrode, the positive electrode, and an electrolytic solution.

The current collector used for the negative electrode and the positive electrode of the nonaqueous electrolyte battery of the present embodiment is not particularly limited as long as it is made of a conductive material. For example, iron, copper, aluminum, nickel, stainless steel, titanium, Metal materials such as tantalum, gold, and platinum can be used. One of these may be used alone, or two or more of these may be used in combination at any ratio.

In this embodiment, a material usually used in a nonaqueous electrolyte battery can be used as the negative electrode. For example, Li, Na, C, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, At least one element selected from the group consisting of Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb, and Bi, an alloy, oxide, chalcogenide, or halide using these elements. used. Further, for example, carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), pitch-based carbon fibers; conductive polymers such as polyacene; composite metal oxidation represented by SiOx, SnOx, LiTiOx And metal compounds such as TiS ₂ , LiTiS _2, and the like.

In this embodiment, a thickener can be further added as necessary. The thickener that can be added is not particularly limited, and various alcohols, in particular, polyvinyl alcohol and modified products thereof, celluloses, starches, and other polysaccharides can be used.

The amount of thickener used is preferably about 0.1 to 4 parts by weight, more preferably 0.3 to 3 parts by weight, and still more preferably 0.5 to 2 parts by weight with respect to 100 parts of the negative electrode active material. It is. If the thickener is excessively small, the viscosity of the slurry composition containing the negative electrode active material and the solvent (hereinafter, also simply referred to as the negative electrode slurry composition) may be too low and the thickness of the mixed layer may be reduced. If there is too much thickener, the discharge capacity may decrease.

Further, examples of the conductive auxiliary compounded in the negative electrode slurry composition as needed include metal powder, conductive polymer, acetylene black, and the like. The amount of the conductive aid used is usually preferably 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight with respect to 100 parts by weight of the negative electrode active material.

In the present embodiment, the negative electrode is prepared by mixing the negative electrode active material as described above with a conductive assistant and a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride in a solvent. The negative electrode slurry thus prepared can be applied to a current collector as described above, for example, a negative electrode current collector such as copper, and the solvent can be dried to obtain a negative electrode.

In the present embodiment, as the positive electrode, a positive electrode usually used for a nonaqueous electrolyte battery is used without any 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 ₁₃ Transition metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ and other lithium-containing composite metal oxides are used. Further, the positive electrode active material is mixed with the same conductive assistant and thickener as the negative electrode, a binder such as SBR, NBR, acrylic rubber, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinylidene fluoride, and the boiling point at normal pressure described above. Can be applied to a positive electrode current collector such as aluminum, and the solvent is dried to form a positive electrode.

The method for applying each electrode slurry composition to the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, and a brush coating method. The amount to be applied is not particularly limited, but the thickness of the mixed layer containing the active material, conductive additive, binder and thickener formed after removing the solvent or dispersion medium by a method such as drying is preferably 0.005 to An amount of 5 mm, more preferably 0.01 to 2 mm is common.

The method for drying a solvent such as water contained in the slurry composition is not particularly limited, and examples thereof include aeration drying with hot air, hot air, and low-humidity air; vacuum drying; drying with infrared rays, far infrared rays, electron beams, and the like. . The drying conditions are preferably adjusted so that the solvent can be removed as soon as possible while the active material layer is cracked by stress concentration or the active material layer does not peel from the current collector. Furthermore, in order to increase the density of the active material of the electrode, it is effective to press the current collector after drying. Examples of the pressing method include a die press and a roll press.

In the nonaqueous electrolyte battery of this embodiment, an electrolytic solution in which an electrolyte is dissolved in a solvent can be used. The electrolyte solution may be liquid or gel as long as it is used for a normal non-aqueous electrolyte battery, and if it appropriately selects a battery that functions as a battery depending on the type of the negative electrode active material and the positive electrode active material. Good. 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, _{_{LiAlC l4, 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 lithium carboxylates.

The solvent for dissolving such an electrolyte (electrolytic solution solvent) 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-butyllactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, and 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 Terigres; diglymes; triglymes; sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone, naphtha sultone, etc. Alternatively, two or more kinds can be mixed and used. 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.

The method for producing the non-aqueous electrolyte battery of the present embodiment is not particularly limited, and for example, the following production method is exemplified. That is, the negative electrode and the positive electrode are overlapped via the separator of the present embodiment described above, wound or folded according to the shape of the battery, put into a battery container, injected with an electrolyte, and sealed. The shape of the battery may be any 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 is less prone to internal short circuit and resistance rise, and is useful for various applications. For example, it is useful as a battery used in portable terminals that are required to be reduced in size, thickness, weight, and performance, and as a battery used in large equipment such as an electric vehicle that requires high safety. Very useful.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

Hereinafter, examples of the present invention will be described, but the present invention is not limited thereto.

Example 1
<Resin composition for separator>
25 g (0.16 mol) of a water-soluble lithium-modified isobutene-maleic anhydride copolymer resin (average molecular weight 325,000, neutralization degree 1.0, ring opening rate 100%) is used as the resin composition for the separator, % Aqueous solution was prepared and used in the following tests. The degree of neutralization was adjusted by adding 2.0 equivalents (0.320 mol) of lithium hydroxide to the maleic acid unit in the maleic acid copolymer.

<Measurement of mass reduction rate>
Thermogravimetry of the α-olefin-maleic acid copolymer was performed using a thermal analyzer (manufactured by Yamato Kagaku Co., Ltd.). As a result of measurement at a measurement temperature range of 50 ° C. to 1000 ° C. and a heating rate of 20 ° C./min, the mass reduction rate at 150 ° C. was 0.3%. The results are shown in Table 1 below.

<Production of coated separator>
The 10% by weight separator resin composition was diluted to 5% by weight as a separator substrate surface coating solution, and a separator (27 cm × 25 cm, non-woven fabric) was immersed in the diluted solution. Using a manual mangle for experiment (manufactured by Kumagai Riki Kogyo Co., Ltd.), the separator coated with the diluent for the separator substrate surface coating solution was squeezed and then dried at room temperature for 12 hours. The dried sheet was pressed with a hot press (manufactured by Furukawa Seisakusho) and adjusted to a thickness of 20 μm (roll temperature room temperature, speed 1 m / min, linear pressure 100 hg / cm). The adhesion amount was 2.1 g / m ² .

<Preparation of slurry for negative electrode>
The slurry for the electrode was prepared by using a solid dispersion of a 48.3 wt% aqueous dispersion of styrene-butadiene rubber (SBR, TRD2001, manufactured by JSR) as a binder with respect to 94 parts by weight of natural graphite (DMGS, manufactured by BYD) as an active material. 3 parts by weight, 1 part by weight of a 1% by weight aqueous solution of carboxymethylcellulose sodium (CMC, Cellogen BSH-6, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and Super-P as a conductive auxiliary agent (conducting agent) 2 parts by weight (made by Timcal Co.) as a solid content was put into a special container and kneaded using a planetary stirrer (ARE-250, manufactured by Sinky). The composition ratio of the active material, the conductive additive and the binder (SBR-CMC) in the slurry is, as a solid content, natural graphite: conductive auxiliary agent: SBR: CMC = 94: 2: 3: 1.

<Preparation of negative electrode for battery>
The obtained slurry was coated on a current collector copper foil (CST8G, manufactured by Fukuda Metal Foil Co., Ltd.) using a bar coater (T101, manufactured by Matsuo Sangyo Co., Ltd.) so that the coating amount was 8.1 mg / cm ^2. After the primary drying with a hot air dryer (manufactured by Yamato Kagaku) at 80 ° C. for 30 minutes, rolling was performed using a roll press (manufactured by Hosen). Then, after punching out as a battery electrode (φ14 mm), a coin battery electrode was produced by secondary drying under reduced pressure conditions at 120 ° C. for 3 hours.

<Preparation of slurry for positive electrode>
The slurry for the electrode is made of 92 parts by weight of nickel / cobalt / manganese (NCM) as an active material, 5 parts by weight of polyvinylidene fluoride (PVDF) as a solid as a binder, and Denka as a conductive additive (conductivity imparting agent). 3 parts by weight of black (powder, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a solid was put into a special container and kneaded using a planetary stirrer (ARE-250, manufactured by Shinky Corporation). In order to adjust the viscosity of the slurry, an electrode coating slurry was prepared by adding water at the time of kneading and kneading again. The composition ratio of the active material and the binder in the slurry is, as a solid content, graphite powder: conductive aid: binder composition = 92: 3: 5.

<Preparation of positive electrode for battery>
The obtained slurry was coated on a current collector aluminum foil (IN30-H, manufactured by Fujishi Paper) using a film applicator (manufactured by Tester Sangyo), and hot air dryer (manufactured by Yamato Scientific) for 30 minutes at 80 ° C. After the primary drying, rolling was performed using a roll press (made by Hosen). Then, after punching out as a battery electrode (φ14 mm), a coin battery electrode was produced by secondary drying under reduced pressure conditions at 120 ° C. for 3 hours.

<Production of battery>
The coated separator and battery negative electrode obtained above were transferred to a glove box (Miwa Seisakusho) under an argon gas atmosphere. The positive electrode, negative electrode, and electrolyte prepared above were lithium hexafluorophosphate (LiPF ₆ ) ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate solution (1 mol / L LiPF ₆ , EC / DMC / EMC = 1/1 / A coin battery (2032 type) was produced using 1).

<Evaluation method: charge / discharge characteristic test>
The produced coin battery was subjected to a charge / discharge test using a commercially available charge / discharge tester (TOSCAT3100, manufactured by Toyo System). The coin battery was placed in a constant temperature bath at 25 ° C., and constant current charging at 0.2 C (about 0.5 mA / cm ² ) was performed until the battery voltage reached 4.2V. The capacity at this time was defined as a charging capacity (mAh). Next, constant current discharge of 0.2 C (about 0.5 mA / cm ² ) was performed until the battery voltage reached 3V. The capacity at this time was defined as a discharge capacity (mAh). The difference between the initial discharge capacity and the charge capacity was taken as the irreversible capacity, and the percentage of the discharge capacity / charge capacity was taken as the charge / discharge efficiency. As the direct current resistance of the coin battery, a resistance value after being charged once (fully charged state) was adopted. The results are shown in Table 1 below.

Among 20 coin batteries produced by the above production method, 2 coin batteries were short-circuited. The results are shown in Table 1 below.

(Example 2)
A 10% by weight aqueous solution of a water-soluble lithium-modified isobutene-maleic anhydride copolymer resin (average molecular weight 325,000, neutralization degree 0.5, ring opening rate 96%) was prepared as a resin composition for a separator. The neutralization degree was adjusted by adding 1.0 equivalent (0.160 mol) of lithium hydroxide to the maleic acid unit in the maleic acid copolymer. A coated separator was produced in the same manner as in Example 1 above. The adhesion amount was 1.8 g / m ² . Further, a negative electrode for a battery was prepared by the same method as in Example 1 to obtain a coin battery, and a charge / discharge characteristic test was performed. The results are shown in Table 1 below.

As a result of measuring the mass reduction rate of the α-olefin-maleic acid copolymer by the same method as in Example 1, the mass reduction rate at 150 ° C. was 0.5%. The results are shown in Table 1 below.

(Example 3)
A 10% by weight aqueous solution of a water-soluble lithium-modified isobutene-maleic anhydride copolymer resin (average molecular weight 325,000, neutralization degree 0.3, ring opening rate 82%) was prepared as a resin composition for a separator. The degree of neutralization was adjusted by adding 0.60 equivalent (0.096 mol) of lithium hydroxide to the maleic acid unit in the maleic acid copolymer. A coated separator was produced in the same manner as in Example 1 above. The adhesion amount was 1.9 g / m ² . Further, a negative electrode for a battery was prepared by the same method as in Example 1 to obtain a coin battery, and a charge / discharge characteristic test was performed. The results are shown in Table 1 below.

As a result of measuring the mass reduction rate of the α-olefin-maleic acid copolymer by the same method as in Example 1, the mass reduction rate at 150 ° C. was 1.2%. The results are shown in Table 1 below.

(Comparative Example 1)
As a resin composition for a separator, 4 parts by weight of SBR of a 48.3% by weight aqueous solution as a solid content and 1 part by weight of a 1.0% by weight aqueous solution of CMC-Na as a solid content were used. It was produced by the same method. The adhesion amount was 1.9 g / m ² . Further, a negative electrode for a battery was prepared by the same method as in Example 1 to obtain a coin battery, and a charge / discharge characteristic test was performed. The results are shown in Table 1 below.

As a result of measuring the mass reduction rate of carboxymethylcellulose sodium salt (CMC-Na) by the same method as in Example 1, the mass reduction rate at 150 ° C. was 7.1%. The results are shown in Table 1 below.

(Comparative Example 2)
A coated negative electrode was produced by the same method as in Example 1 without using a separator substrate surface coating solution, to obtain a coin battery, and a charge / discharge characteristic test was performed. The results are shown in Table 1 below.

(Comparative Example 3)
As a resin composition for a separator, a coated separator was formed as in Example 1 above using 50% Na salt of a 51.2 w% aqueous solution of polyacrylic acid (average molecular weight 187,000, degree of neutralization 0.5, manufactured by Aldrich) as a solid content. It produced by the same method. The adhesion amount was 2.1 g / m ² . Further, a negative electrode for a battery was prepared by the same method as in Example 1 to obtain a coin battery, and a charge / discharge characteristic test was performed. The results are shown in Table 1 below.

(Discussion)
In Examples 1 to 3 using the separator coated with the separator substrate surface coating solution using the separator resin composition of the present invention, the α-olefin-maleic acid copolymer compensates for the defects of the separator and reduces short-circuiting. As a result, the yield was improved. On the other hand, it was easy to short-circuit about the separator (Comparative Example 2) which was not coat | covered.

The separator coated with the separator substrate surface coating solution was equivalent to the case where a separator not coated with electrical resistance was used, but when SBR / CMC-Na used for general purpose was used (Comparative Example) 1) It has been shown that resistance increases and battery performance also decreases. It is considered that the neutralized salt of the α-olefin-maleic acid copolymer constituting the separator substrate surface coating solution improves ion transmission in the battery.
Furthermore, in Comparative Example 3 using polyacrylic acid, which is also an ordinary product, it can be seen that the DC resistance is high despite having a carboxylic acid moiety as in the present invention.

This application is based on Japanese Patent Application No. 2015-156188 filed on August 6, 2015, the contents of which are included in this application.

In order to express the present invention, the present invention has been described appropriately and sufficiently through the embodiments with reference to the drawings and the like. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that it can be done. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

The present invention has wide industrial applicability in the technical field of non-aqueous electrolyte batteries.

Claims

a neutralized salt of an α-olefin-maleic acid copolymer obtained by copolymerization of an α-olefin and maleic acid, and the degree of neutralization of the carboxylic acid generated from the maleic acid in the copolymer is 0.3. A resin composition for a non-aqueous electrolyte battery separator, wherein the resin composition is 1.0 to 1.0.
A separator for a nonaqueous electrolyte battery comprising a coating layer made of the resin composition for a separator according to claim 1.
A nonaqueous electrolyte battery comprising the separator according to claim 2.