JP2012014994A - Separator for nonaqueous electrolyte battery and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator used for constituting a nonaqueous electrolyte battery which exhibits excellent safety and reliability for internal short circuit and is capable of minimizing characteristic degradation during high-temperature storage, and to provide a nonaqueous electrolyte battery having that separator.SOLUTION: The separator used in a nonaqueous electrolyte battery contains a polyamine group represented by a general formula -NH(CHCHNH)R [in the general formula (1), n is a positive integer, R is H or an alkyl group of 1-10C], and contains particulates having a mean particle size of 0.01-15 μm. The nonaqueous electrolyte battery having that separator is also provided.

Description

  The present invention relates to a separator for constituting a non-aqueous electrolyte battery that is excellent in safety and reliability and that can suppress a decrease in performance during high-temperature storage, and a non-aqueous electrolyte battery having the separator.

  A non-aqueous electrolyte battery using a non-aqueous electrolyte typified by a lithium secondary battery is widely used as a power source for portable devices such as mobile phones and notebook personal computers because of its high energy density. In such non-aqueous electrolyte batteries, there is a tendency for the capacity to increase further as the performance of portable devices increases, and it is important to ensure safety and reliability. Non-aqueous electrolyte batteries are also being applied to in-vehicle applications such as automobiles, motorcycles, and bicycles by taking advantage of the characteristics such as high energy density. Even in such applications, safety and reliability can be ensured. It is an important issue.

  Lithium secondary batteries have a feature that the potential per unit cell is higher than other batteries. However, when there is a foreign material such as metal, dissolution and precipitation occur in the battery and deposit at the negative electrode. As the metal grows and breaks through the separator and short-circuits, reliability and safety may be impaired.

In addition, a lithium secondary battery that has been generally used conventionally uses a lithium cobalt composite oxide having a layered structure typified by LiCoO ₂ as a positive electrode active material, and a carbon material such as graphite or amorphous graphite as a negative electrode. Generally, a non-aqueous electrolytic solution in which a lithium salt such as LiPF ₆ is dissolved in a carbonate such as ethylene carbonate or diethyl carbonate is used as an active material. However, in recent years, in order to increase the thermal stability to ensure safety, or to increase the energy density by operating at a higher potential, spinel type lithium manganese composite oxide represented by LiMn ₂ O ₄ , Layered compounds typified by LiMn _q Ni _r Co ₅ O ₂ have come to be used as positive electrode active materials.

  However, when a composite oxide containing Mn is used for the positive electrode, the Mn ions are eluted from the positive electrode particularly at a high temperature, leading to a decrease in the capacity of the positive electrode. It is known that side reactions other than those related to charge / discharge occur due to degradation of the liquid or reaction with a non-aqueous electrolyte to cause gas generation.

  Various techniques for solving the problems caused by metal (metal ions) eluted from the metal foreign matter and the positive electrode active material have been studied. For example, Patent Literature 1 and Patent Literature 2 propose a technique for stabilizing a positive electrode active material using a substitution element and preventing elution of a metal such as Mn.

  Patent Documents 3 and 4 propose a technique for trapping mixed metal foreign substances and metal ions eluted from the positive electrode before reaching the negative electrode.

JP 11-339803 A JP 2000-30709 A Japanese Patent Application Laid-Open No. 11-121021 JP 2009-87929 A

  However, although the modification of the active material using a substitution element as described in Patent Document 1 and Patent Document 2 has a certain effect on metal elution, elution cannot be completely suppressed, In addition, there is a demerit that the capacity that can be used for charging and discharging is reduced by the substitution element.

  In addition, as a method of trapping gold ions in the battery, for example, as shown in Patent Document 3, in a method of containing a chelating agent in at least one of a negative electrode, a separator and an electrolyte, the added chelating agent is There is a possibility that a side reaction is caused by an oxidation-reduction reaction in the positive electrode or the negative electrode, and the battery characteristics are deteriorated.

  Furthermore, in the method of containing a chelate compound in a separator that is relatively unaffected by the oxidation and reduction shown in Patent Document 4, iminodiacetic acid groups in the chelate compound may trap lithium ions in the battery. There is.

  For these reasons, there is a need for development of a technology that can satisfactorily avoid problems caused by metal ions in the battery while suppressing the occurrence of such secondary problems.

  The present invention has been made in view of the above circumstances, and its object is to configure a nonaqueous electrolyte battery that is excellent in safety and reliability against internal short circuit and can suppress deterioration in characteristics during high-temperature storage. The object is to provide a separator and a nonaqueous electrolyte battery having the separator.

  The separator for a non-aqueous electrolyte battery of the present invention that has achieved the above object is a separator used for a non-aqueous electrolyte battery, contains a polyamine group represented by the following general formula (1), and has an average particle diameter. It contains 0.01 to 15 μm fine particles.

—NH (CH ₂ CH ₂ NH) _n R (1)
[In the general formula (1), n is a positive integer, and R is H or an alkyl group having 1 to 10 carbon atoms. ]

  The non-aqueous electrolyte battery of the present invention is a non-aqueous electrolyte battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte solution, wherein the separator is the non-aqueous electrolyte battery separator of the present invention. To do.

  ADVANTAGE OF THE INVENTION According to this invention, the separator for comprising the nonaqueous electrolyte battery which is excellent in safety | security and the reliability with respect to an internal short circuit, and can suppress the characteristic fall at the time of high temperature storage, and a nonaqueous electrolyte battery which has this separator are provided. can do. That is, the nonaqueous electrolyte battery of the present invention is excellent in safety and reliability against internal short circuit, and can suppress deterioration in characteristics during high-temperature storage.

  The separator according to the nonaqueous electrolyte battery of the present invention includes fine particles containing a polyamine group represented by the general formula (1) (hereinafter sometimes abbreviated as “polyamine group-containing fine particles”). The polyamine group represented by the general formula (1) present in the separator can effectively trap metal ions eluted in the non-aqueous electrolyte of the battery.

  In non-aqueous electrolyte batteries, especially non-aqueous electrolyte batteries such as rechargeable lithium ion batteries, metal ions eluted into the non-aqueous electrolyte from the metal impurities and positive electrode active materials mixed in the battery Precipitation tends to cause deterioration of battery performance and internal short circuit. Therefore, in particular, while effectively trapping ions such as Ni, Co and Mn, which are used as main components in the positive electrode active material, and Fe, Zn and Cu, which are likely to be mixed into the battery as impurities, It is preferable not to trap Li ions involved in charging / discharging of the battery as much as possible. The polyamine group represented by the general formula (1) is excellent in trapping ability for transition metals and heavy metals, but has low trapping ability for alkali metals and alkaline earth metals. For this reason, in the battery of the present invention, the presence of the polyamine group represented by the general formula (1) present in the separator causes metal ions that cause deterioration in battery performance and internal short circuit without impairing the charge / discharge reaction. Can be trapped well.

  In addition, although n in the said General formula (1) is a positive integer, it is preferable that it is 1 or more, it is more preferable that it is 2 or more, and it is preferable that it is 6 or less, and it is 5 or less. It is more preferable.

The amount of the polyamine group related to the polyamine group-containing fine particles in the separator is preferably 0.01 to 100 mmol / m ² in terms of the amount of NH groups from the viewpoint of ensuring a good trapping ability for metal ions.

  The polyamine group-containing fine particles may be inorganic fine particles (fine particles in which a portion other than the polyamine group is composed of an inorganic material) or organic fine particles. The separator contains inorganic fine particles containing a polyamine group represented by the general formula (1) (hereinafter referred to as “polyamine group-containing inorganic fine particles”) and a polyamine group represented by the general formula (1). Organic fine particles (hereinafter referred to as “polyamine group-containing organic fine particles”) may be included.

  Examples of the polyamine group-containing inorganic fine particles and the polyamine group-containing organic fine particles include inorganic fine particles and organic fine particles [inorganic fine particles and organic fine particles not containing a polyamine group represented by the general formula (1)], Examples thereof include those obtained by surface treatment using a coupling agent which is a base of the polyamine group represented by the general formula (1). Further, the polyamine group-containing organic fine particles may be fine particles composed of an organic resin containing a polyamine group represented by the general formula (1).

The inorganic fine particles used as the base material for the polyamine group-containing inorganic fine particles are not particularly limited as long as they are electrochemically stable and electrically insulating. For example, the inorganic fine particles of iron oxide _{(Fe x} O y; FeO, such _{Fe 2 O 3), SiO 2} , Al 2 O 3, TiO 2, BaTiO 3, inorganic oxides such as ZrO _2; aluminum nitride, silicon nitride Inorganic nitrides such as: Calcium fluoride, barium fluoride, barium sulfate, calcium carbonate and other poorly soluble ionic crystals; Silicon, diamond and other covalently bonded crystals; Montmorillonite and other clays; Here, the inorganic oxide may be boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, mica, or other mineral resource-derived substances or artificial products thereof. In addition, the surface of a conductive material exemplified by metal, SnO ₂ , conductive oxide such as tin-indium oxide (ITO), carbonaceous material such as carbon black, graphite, etc., is a material having electrical insulation ( For example, the particle | grains which gave the electrical insulation property by coat | covering with the said inorganic oxide etc. may be sufficient. The inorganic fine particles may be used alone or in combination of two or more. Among the inorganic oxides, Al ₂ O ₃ , SiO ₂ and boehmite are particularly preferably used.

The shape of the inorganic fine particles may be, for example, a nearly spherical shape or a plate shape, but from the viewpoint of better preventing a short circuit (especially a short circuit due to dendrites) Preferably there is. Typical examples of the plate-like particles include plate-like Al ₂ O ₃ and plate-like boehmite, and these may be used alone or in combination of two or more.

  The organic fine particles used as the base material of the polyamine group-containing organic fine particles have heat resistance and electrical insulation, are stable to the non-aqueous electrolyte of the battery, and are oxidized within the operating voltage range of the battery. What was comprised with the electrochemically stable material which cannot be reduced easily is preferable, and as such a material, a resin crosslinked body is mentioned, for example. More specifically, styrene resin (polystyrene (PS), etc.), styrene butadiene rubber (SBR), acrylic resin (polymethyl methacrylate (PMMA), etc.), polyalkylene oxide (polyethylene oxide (PEO), etc.), fluororesin [ Polyvinylidene fluoride (PVDF) and the like] and a crosslinked product of at least one resin selected from the group consisting of these derivatives; urea resin; polyurethane; and the like. In the organic fine particles, the above exemplified resins may be used alone or in combination of two or more. Moreover, the organic fine particles may contain various known additives that are added to the resin, for example, an antioxidant, if necessary.

  Among the materials for constituting the organic fine particles serving as the base material, a crosslinked styrene resin, a crosslinked acrylic resin, and a crosslinked fluororesin are preferable, and crosslinked PMMA is particularly preferable.

Examples of the coupling agent used for treating the surface of the inorganic fine particles and organic fine particles serving as the base material and introducing the polyamine group represented by the general formula (1) include silane coupling agents and zirco. Examples of the coupling agent include titanate coupling agents and titanate coupling agents. More specifically, H ₂ NCH ₂ CH ₂ NHCH ₂ CHCH ₂ X (OCH ₃ ) ₃ , H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ X (OCH ₃ ) ₃ , H ₂ NCH ₂ CH ₂ NHCH _{2 CH 2 CH 2 X (OC 2} H 5) 3, H 2 NCH 2 CH 2 NHCH 2 PhCH 2 CH 2 X (OCH 3) 3, H 2 NCH 2 CH 2 NH (CH 2) 11 X (OCH 3) 3 , (CH ₃ O) ₃ SiCH ₂ CH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ X (OCH ₃ ) ₃ , H ₂ NC ₂ H ₄ NHC ₂ H ₄ OXO [CH (CH ₃ ) CH ₃ ] ₃ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ SiCH ₃ (OCH ₃ ) ₂ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ Si (OCH ₃ ) ₃ , H ₂ NC ₂ H ₄ NHC ₃ H ₆ Si (OC ₂ H ₅ ) _{3 and the} like are mentioned (in the above formulas representing exemplary coupling agents, X represents Si, Zr or Ti, and Ph represents phenylene). .

  When the polyamine group-containing fine particles are composed of an organic resin containing a polyamine group represented by the general formula (1), examples of the organic resin include Japanese Patent Publication No. 6-51744 and Japanese Patent No. 3150173. Examples thereof include organic resins obtained by a method described in Japanese Patent Laid-Open No. 2005-213477.

  If the average particle size of the polyamine group-containing fine particles is too small, the pore size of the separator (the porous layer containing the polyamine group-containing fine particles) becomes too small, and the ion permeability of lithium ions and the like may be reduced. , 0.01 μm or more, and preferably 0.1 μm or more. However, if the particle size of the polyamine group-containing fine particles is too large, the separator (the porous layer containing the polyamine group-containing fine particles) becomes too thick, resulting in a decrease in energy density when used as a battery or a specific surface area of the particles. The average particle size of the polyamine group-containing fine particles is 15 μm or less, and preferably 5 μm or less, because the trapping ability of metal ions may become too low.

  The average particle size of the fine particles (polyamine group-containing fine particles, inorganic fine particles used in the heat shrinkage suppression layer described later, and heat-meltable fine particles and heat-swellable fine particles described later) referred to in the present specification is, for example, laser scattering particle size distribution Using a meter (for example, “LA-920” manufactured by HORIBA), in the case of inorganic fine particles, in a medium that does not dissolve them, in the case of organic fine particles, in a medium that does not swell these constituent resins (for example, water) It can be defined as the number average particle size measured by dispersing fine particles. Unless otherwise specified, the secondary particle-like fine particles mean the average particle size of the secondary particles.

  The separator of this invention should just contain the polyamine group containing microparticles | fine-particles, for example, the separator of this invention can be comprised with the porous film formed by binding these microparticles | fine-particles with a binder.

  Examples of the binder for binding the polyamine group-containing fine particles include ethylene-vinyl acetate copolymer (EVA, vinyl acetate-derived structural unit having 20 to 35 mol%), ethylene-ethyl acrylate copolymer, and the like. Ethylene-acrylic acid copolymer, fluorinated rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linking Acrylic resin, polyurethane, epoxy resin and the like can be mentioned, and in particular, a heat-resistant binder having a heat-resistant temperature of 150 ° C. or higher is preferably used. As the binder, those exemplified above may be used alone or in combination of two or more.

  Among the binders exemplified above, highly flexible binders such as EVA, ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are preferable. Specific examples of such highly flexible binders include “Evaflex Series (EVA)” by Mitsui DuPont Polychemical Co., Ltd., EVA by Nippon Unicar Co., Ltd., “Evaflex-EEA Series (Ethylene- Acrylic acid copolymer) ”, Nippon Unicar's EEA, Daikin Industries’ “Dai-L Latex Series” (fluorinated rubber), JSR ’s “TRD-2001 (SBR)”, Nippon Zeon ’s “BM-400B” SBR) "and the like.

  The content of the polyamine group-containing fine particles in the separator is the total volume of the constituent components of the separator (total volume of the portion excluding the separator voids) from the viewpoint of better ensuring the effect of trapping metal ions in the battery. Among them, the content is preferably 5% by volume or more, and more preferably 10% by volume or more. Further, the upper limit value of the content of the polyamine group-containing fine particles represented by the general formula (1) in the separator is not particularly limited. For example, as described above, the separator of the present invention includes polyamine group-containing fine particles and Since it is possible to use only a binder, the entire amount excluding the binder can be made into polyamine group-containing fine particles. A suitable upper limit value of the polyamine group-containing fine particles in the case of such a separator is, for example, 99% by volume.

  In addition, the separator of the present invention, which is generally used for non-aqueous electrolyte batteries, closes the vacancies when the battery temperature rises, lowers the ion permeability, and reduces battery safety. It is possible to provide a so-called shutdown function for ensuring the above.

  For example, by using a separator composed of a multilayer porous film in which a porous layer containing polyamine group-containing fine particles is formed on the surface of a porous film mainly made of polyolefin having a shutdown function (such as a microporous film made of polyolefin). A shutdown function can be given.

  When a separator is provided with a shutdown function by being constituted by a multilayer porous membrane using a polyolefin microporous membrane, a separator used in a normal non-aqueous electrolyte battery may be used for the polyolefin microporous membrane. it can. Specifically, a microporous film composed of a copolymer polyolefin such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer can be used.

  The microporous membrane made of polyolefin is composed of the polyolefin as described above. For example, a film or sheet formed by a stretching method, that is, a polyolefin mixed with an inorganic filler is uniaxially or biaxially stretched to form a fine film. After forming the pores, those produced by removing the inorganic filler as required can be used. In addition, the pore formation method using a solvent, that is, the polyolefin illustrated above and another resin or paraffin are mixed to form a film or sheet, and then, in a solvent that dissolves only the other resin or paraffin, What is manufactured by immersing a film or sheet and dissolving only the other resin or paraffin to form pores can be used as a polyolefin microporous film. Furthermore, a polyolefin microporous membrane produced by a method combining the stretching method and the pore formation method using the solvent can also be used.

  If the temperature at which the shutdown function is exhibited in the separator is too low, the separator hole may be blocked during normal use of the battery, and the battery performance may deteriorate quickly. It is more preferable that In addition, if the temperature at which the shutdown function is manifested in the separator is too high, there is a risk that the internal temperature of the battery will rise before the shutdown function works, leading to thermal runaway. It is more preferable that it is below ℃.

  When a separator is constituted by a multilayer porous film comprising a porous film mainly composed of polyolefin (such as a microporous film made of polyolefin) and a porous layer containing polyamine group-containing fine particles, the multilayer porous film contains a polyamine group. The porous layer containing fine particles may be provided only on one side of the porous film mainly composed of polyolefin, or may be provided on both sides.

  In addition, since the polyolefin content in the porous membrane mainly composed of polyolefin such as a microporous membrane made of polyolefin is mainly composed of polyolefin, it is 50% by volume or more in the total volume of the constituent components of the porous membrane. 70% by volume or more, preferably 100% by volume, that is, it may be composed of polyolefin alone.

  Further, the content of the polyamine group-containing fine particles in the porous layer containing the polyamine group-containing fine particles formed on the surface of the porous film mainly composed of polyolefin is 50% by volume or more in the total volume of the constituent components of the porous layer. It is preferable that it is 70 volume% or more, and it is preferable that it is 99 volume% or less.

  In addition to the polyamine group-containing fine particles, the porous layer containing the polyamine group-containing fine particles may contain, for example, the binder described above in order to bind these fine particles.

  In the separator using the polyolefin microporous membrane, the shutdown function works when the temperature rises, but the polyolefin microporous membrane is usually stretched to have a microporous structure as described above. Therefore, thermal shrinkage may occur due to the residual stress due to stretching when the temperature rises simultaneously with the shutdown. Therefore, in the case of a separator using a polyolefin microporous membrane, in addition to forming a porous layer containing polyamine group-containing microparticles on one side of the polyolefin microporous membrane, the other side is provided with inorganic microparticles. A porous layer (heat shrinkage suppression layer) included as a main body may be formed to suppress heat shrinkage of the entire separator.

  Examples of the inorganic fine particles used in the heat shrinkage suppression layer include various inorganic fine particles exemplified above as inorganic fine particles serving as a base material for the polyamine group-containing fine particles. The average particle size of the inorganic fine particles used for the heat shrinkage suppression layer is preferably 0.01 μm or more, more preferably 0.1 μm or more, and preferably 15 μm or less, and 5 μm or less. Is more preferable.

  However, if the content of the inorganic fine particles in the heat shrinkage suppression layer is too small, the action of suppressing the heat shrinkage of the entire separator may be reduced. The above is preferable, and 80% by volume or more is more preferable. In addition, the heat shrinkage suppression layer is preferably constituted by, for example, binding inorganic fine particles with a binder, and the content of inorganic fine particles in the heat shrinkage suppression layer can be the total amount excluding the binder. In the total volume of the constituent components of the heat shrinkage suppression layer, it is preferably 99% by volume or less.

  In addition, the binder used for a heat-shrinkage suppression layer can use the various binders illustrated previously as a binder for binding of polyamine group-containing fine particles.

  When the polyamine group-containing fine particles are inorganic fine particles (the base material of the polyamine group-containing fine particles is an inorganic fine particle), the porous layer containing the polyamine group-containing fine particles can also serve as a heat shrinkage suppression layer.

  In order to give the separator of the present invention a shutdown function, in addition to the above method, the separator contains resin fine particles having a melting point in the preferred temperature range in which the shutdown function is exhibited (hereinafter referred to as “heat-meltable fine particles”). Can be adopted.

  As the constituent resin of the heat-meltable fine particles, an electrochemical material having a melting point in the above temperature range, stable to the electrolyte solution of the nonaqueous electrolyte battery, and hardly oxidized / reduced in the battery operating voltage range. Stable resin is preferable. Specific examples include PE, copolymerized polyolefin, polyolefin derivatives (such as chlorinated polyethylene), polyolefin wax, petroleum wax, and carnauba wax. Examples of the copolymer polyolefin include ethylene-vinyl monomer copolymers, more specifically ethylene-acrylic copolymers such as ethylene-propylene copolymers, EVA, ethylene-methyl acrylate copolymers, and ethylene-ethyl acrylate copolymers. An acid copolymer can be illustrated. The structural unit derived from ethylene in the copolymerized polyolefin is desirably 85 mol% or more. Moreover, polycycloolefin etc. can also be used. As the heat-meltable fine particles, one of the above exemplified resins may be used alone, or two or more of them may be used.

  Among the materials exemplified above, PE, polyolefin wax, or EVA having a structural unit derived from ethylene of 85 mol% or more is preferably used as the heat-meltable fine particles. Moreover, the heat-meltable fine particles may contain various known additives (for example, antioxidants) added to the resin as necessary.

  The melting point of the heat-meltable fine particles can be determined from the melting temperature measured using a differential scanning calorimeter (DSC), for example, in accordance with JIS K 7121.

  The separator of the present invention can also be shut down by containing fine particles that swell when heated by absorbing the non-aqueous electrolyte and whose degree of swelling increases as the temperature rises (hereinafter referred to as “thermally swellable fine particles”). Functions can be added.

  As the heat-swellable fine particles, in the temperature range (about 70 ° C. or less) in which the battery is usually used, the electrolyte solution is not absorbed or the amount of absorption is limited, and thus the degree of swelling is below a certain level. When heated to the required temperature (Tc), fine particles composed of a resin having such a property that it absorbs the non-aqueous electrolyte and swells greatly and the degree of swelling increases as the temperature rises are used. In a non-aqueous electrolyte battery using a separator containing heat-swellable fine particles, a flowable non-aqueous electrolyte solution that is not absorbed by the heat-swellable fine particles is present in the pores of the separator at a temperature lower than Tc. Although the non-aqueous electrolyte battery has good load characteristics due to high internal Li ion conductivity, it has the property of increasing the degree of swelling as the temperature rises (hereinafter sometimes referred to as “thermal swelling”). When heated above the temperature at which it appears, the heat-swellable fine particles absorb the non-aqueous electrolyte in the battery and swell greatly, and the swollen heat-swellable fine particles close the pores of the separator and are non-flowable. By reducing the amount of water electrolyte and causing the non-aqueous electrolyte battery to wither, the reactivity between the non-aqueous electrolyte and the active material is suppressed, and the safety of the non-aqueous electrolyte battery is ensured. In addition, when the temperature is higher than Tc, the liquid withering further proceeds due to thermal swellability, and the reaction of the battery is further suppressed, so that safety at high temperature can be further improved.

  The temperature at which the heat-swellable fine particles start to show heat-swellability is preferably 75 ° C. or higher. By setting the temperature at which the heat-swellable fine particles start to exhibit heat-swellability to 75 ° C. or higher, the temperature (Tc) at which the Li ion conductivity is significantly reduced and the internal resistance of the battery is increased is set to approximately 80 ° C. or higher. Because it can be done. On the other hand, since the Tc of the separator increases as the lower limit of the temperature exhibiting thermal swellability increases, the temperature at which the thermal swellable fine particles begin to exhibit thermal swellability is set to 125 ° C in order to set Tc to approximately 130 ° C or lower. It is preferable to set it as follows, and it is more preferable to set it as 115 degrees C or less. If the temperature showing the heat swellability is too high, the thermal runaway reaction of the active material in the battery cannot be sufficiently suppressed, and the safety improvement effect of the nonaqueous electrolyte battery by using the heat-swelling fine particles cannot be sufficiently secured. In addition, if the temperature exhibiting thermal swellability is too low, the conductivity of Li ions may be too low in the operating temperature range of a normal nonaqueous electrolyte battery (approximately 70 ° C. or less).

  Further, at a temperature lower than the temperature exhibiting the heat swellability, it is desirable that the heat swellable fine particles do not absorb the non-aqueous electrolyte as much as possible and have less swelling. This is because, in the operating temperature range of a non-aqueous electrolyte battery, for example, room temperature, the non-aqueous electrolyte solution is more likely to be retained in a flowable state in the pores of the separator than to be taken into the heat-swellable fine particles. This is because characteristics such as load characteristics of the electrolyte battery are improved.

Nonaqueous electrolyte volume heat swellable particles absorb at normal temperature (25 ° C.) can be evaluated by the degree of swelling B _R defined by the following equation representing the change in volume of the heat-swellable particles (2).
B _R = (V ₀ / V _i ) -1 (2)
[In the formula, V ₀ is the volume of the heat-swellable particles after 24 hours immersion at 25 ° C. in the nonaqueous electrolytic solution (cm ^3), V _i is the thermal swelling before immersion in the non-aqueous electrolyte Each represents the volume (cm ³ ) of the fine particles. ]

In case of using heat-swellable particles in the separator of the present invention, the swelling degree B _R of the heat-swellable particles at room temperature (25 ° C.) is preferably 1 or less, swelling is small due to absorption of the electrolyte, that, B _R it is desirable that the smallest possible value close to 0. Further, it is desirable that the temperature change of the degree of swelling is as small as possible on the lower temperature side than the temperature exhibiting thermal swellability. For example, in a separator having a layer in which heat-swellable fine particles are bound with a binder, the degree of swelling of the heat-swellable fine particles may be a small value in the presence of the binder.

On the other hand, as heat-swellable fine particles, when heated above the lower limit of the temperature exhibiting thermal swellability, the amount of non-aqueous electrolyte absorbed increases and swells with temperature in the temperature range exhibiting thermal swellability. The one with increasing degree is used. For example, it is measured at 120 ° C., swelling degree B _T which is defined by the following formula (3) is, as 1 or higher is preferably used.
B _T = (V ₁ / V ₀ ) −1 (3)
[In the above formula, V ₀ is the volume (cm ³ ) of thermally swellable fine particles after immersion in non-aqueous electrolyte at 25 ° C. for 24 hours, and V ₁ is immersed in non-aqueous electrolyte at 25 ° C. for 24 hours. Thereafter, the nonaqueous electrolyte is heated to 120 ° C., and the volume (cm ³ ) of the heat-swellable fine particles after 1 hour at 120 ° C. is shown. ]

  On the other hand, since the degree of swelling of the heat-swellable fine particles defined by the formula (3) may be excessively large, it may cause deformation of the nonaqueous electrolyte battery, and is preferably 10 or less.

  The degree of swelling defined by the above formula (3) is obtained by directly measuring the change in the size of the heat-swellable fine particles using a method such as a light scattering method or an image analysis of an image taken by a CCD camera. Although it can estimate, it can measure more correctly, for example using the following methods.

Using a binder resin having a known degree of swelling at 25 ° C. and 120 ° C., which is defined in the same manner as in the above formula (2) and formula (3), heat-swellable fine particles are mixed with the solution or emulsion to prepare a slurry. And this is apply | coated on base materials, such as a polyethylene terephthalate (PET) sheet and a glass plate, a film is produced, and the mass is measured. Next, the film was immersed in a non-aqueous electrolyte at 25 ° C. for 24 hours to measure the mass, and the non-aqueous electrolyte was heated to 120 ° C. and the mass after holding at 120 ° C. for 1 hour. It was measured to calculate the degree of swelling _{B T} by the equation (4) to (10). In addition, in the following formulas (4) to (10), the volume increase of components other than the non-aqueous electrolyte when the temperature is raised from 25 ° C. to 120 ° C. can be ignored.

V _i = M _i × W / P _A (4)
V _B = (M ₀ −M _i ) / P _B (5)
_{V C = M 1 / P C} -M 0 / P B (6)
V _V = M _i × (1−W) / P _V (7)
V ₀ = V _i + V _B −V _V × (B _B +1) (8)
V _D = V _V × (B _B +1) (9)
B _T = {V ₀ + V _C −V _D × (B _C +1)} / V ₀ −1 (10)
Here, in the formulas (4) to (10),
V _i : Volume of heat-swellable fine particles (cm ³ ) before being immersed in the non-aqueous electrolyte,
V ₀ : volume (cm ³ ) of heat-swellable fine particles after immersion in non-aqueous electrolyte at 25 ° C. for 24 hours,
V _B : volume of the nonaqueous electrolyte absorbed in the film after being immersed in the nonaqueous electrolyte at room temperature for 24 hours (cm ³ ),
V _c : Non-water absorbed in the film during the period from when the non-aqueous electrolyte was immersed in room temperature for 24 hours until the non-aqueous electrolyte was heated to 120 ° C. and further passed at 120 ° C. for 1 hour. Electrolyte volume (cm ³ ),
V _V : volume (cm ³ ) of the binder resin before being immersed in the non-aqueous electrolyte
V _D : volume of the binder resin (cm ³ ) after being immersed in a non-aqueous electrolyte at room temperature for 24 hours,
M _i : mass (g) of the film before being immersed in the non-aqueous electrolyte
M ₀ : mass (g) of the film after being immersed in a non-aqueous electrolyte at room temperature for 24 hours,
M _l : After immersing in a non-aqueous electrolyte at room temperature for 24 hours, the temperature of the non-aqueous electrolyte was raised to 120 ° C., and the mass (g) of the film after 1 hour at 120 ° C.
W: Mass ratio of heat-swellable fine particles in the film before being immersed in the non-aqueous electrolyte,
P _A : specific gravity (g / cm ³ ) of heat-swellable fine particles before being immersed in the non-aqueous electrolyte
P _B : Specific gravity (g / cm ³ ) of non-aqueous electrolyte at room temperature,
P _C: a specific gravity of the nonaqueous solution at a given temperature (g / ^cm 3),
P _V : specific gravity (g / cm ³ ) of the binder resin before being immersed in the non-aqueous electrolyte,
B _B : Swelling degree of binder resin after being immersed in non-aqueous electrolyte at room temperature for 24 hours,
B _C : The degree of swelling of the binder resin at the time of temperature increase defined by the above formula (3).

Also, the V _i and V ₀ obtained from the equation (4) and the equation (8) by the above method, it is possible to obtain the swelling degree B _R at room temperature using the equation (2).

In the nonaqueous electrolyte battery of the present invention, for example, a solution obtained by dissolving a lithium salt in an organic solvent is used as the nonaqueous electrolyte, as in the case of conventionally known nonaqueous electrolyte batteries (lithium salt or organic solvent). The details of the type and the lithium salt concentration will be described later). Therefore, as the heat-swellable particles, in an organic solvent solution of lithium salt, it began to show the heat-swellable upon reaching any temperature 75 to 125 ° C., preferably swelling degree B _R in solution in And those in which B _T can swell to satisfy the above values are recommended.

  The heat-swellable fine particles are heat-resistant and electrically insulating, stable against non-aqueous electrolytes, and are electrochemically stable materials that are not easily oxidized or reduced in the battery operating voltage range. Such a material is preferably configured, and examples of such a material include various resins (resin cross-linking) exemplified above as resins (resin cross-linked bodies) for forming organic fine particles serving as a base material for polyamine group-containing organic fine particles. Body). For the heat-swellable fine particles, the above exemplified resins may be used alone or in combination of two or more. The heat-swellable fine particles may contain various known additives that are added to the resin, for example, an antioxidant, as necessary.

  Among the constituent materials, a crosslinked styrene resin, a crosslinked acrylic resin, and a crosslinked fluororesin are preferable, and crosslinked PMMA is particularly preferably used.

  The mechanism by which these resin crosslinked bodies absorb and swell the non-aqueous electrolyte as the temperature rises is not clear, but a correlation with the glass transition point (Tg) is conceivable. That is, since the resin generally becomes flexible when heated to its Tg, it is estimated that the resin as described above can absorb a large amount of non-aqueous electrolyte and swell at temperatures above Tg. The Therefore, as the heat-swellable fine particles, it is desirable to use a crosslinked resin having a Tg of about 75 to 125 ° C. in consideration of the fact that the temperature at which the shutdown action actually occurs is somewhat higher than the temperature at which the heat-swellability begins to be exhibited. it is conceivable that. In addition, Tg of the resin crosslinked body which is a heat-swellable fine particle as used in the present specification is a value measured using DSC in accordance with the provisions of JIS K7121.

  In the so-called dry state before containing the non-aqueous electrolyte, the resin cross-linked body is reversible to some extent to the volume change accompanying the temperature change, such as expansion due to temperature rise and contraction again by lowering the temperature. In addition, since it has a heat-resistant temperature that is considerably higher than the temperature that exhibits thermal swellability, it can be heated to 200 ° C or higher even if the lower limit of the temperature that exhibits thermal swellability is about 100 ° C. The material can be selected. Therefore, even when heating is performed in a separator manufacturing process or the like, the resin is not dissolved or the thermal swellability of the resin is not impaired, and handling in a manufacturing process including a general heating process becomes easy.

  In addition, about heat-swellable microparticles | fine-particles, polyamine group containing microparticles | fine-particles (polyamine group containing organic microparticles | fine-particles) can be made by including the polyamine group represented by the said General formula (1) by performing surface treatment by the said method. Can be used.

  The heat-meltable fine particles and heat-swellable fine particles may be used, for example, by being contained in a separator made of a porous film containing polyamine group-containing fine particles and a binder, whereby a separator having a shutdown function can be obtained. it can.

  The heat-meltable fine particles and the heat-swellable fine particles may have an average particle size that is 1/100 to 1/3 of the thickness of the separator, although their particle size at the time of drying may be smaller than the thickness of the separator. Specifically, the average particle size of the heat-meltable fine particles and heat-swellable fine particles is preferably 0.1 to 20 μm. When the particle diameter of the heat-meltable fine particles or the heat-swellable fine particles is too small, the gap between the particles becomes small, the ion conduction path becomes long, and the battery characteristics may be deteriorated. On the other hand, if the particle size is too large, the separator becomes thick, and the energy density of the battery may be reduced.

  The shape of the polyamine group-containing fine particles, the inorganic fine particles used in the heat shrinkage suppression layer, the heat-meltable fine particles, and the heat-swellable fine particles is not particularly limited, but is porous mainly composed of polyolefin such as a polyolefin microporous film. When a heat shrinkage suppression layer mainly containing inorganic fine particles or a porous layer containing polyamine group-containing fine particles that also function as a heat shrinkage suppression layer is provided on the surface of the film, the polyamine contained in these heat shrinkage suppression layers The group-containing fine particles and the inorganic fine particles are preferably in the form of secondary particles in which plate-like particles or primary particles are connected from the viewpoint of further enhancing the action of suppressing the heat shrinkage of the entire separator in the heat shrinkage suppressing layer.

  Also, as will be described later, when the separator of the present invention is directly formed on the surface of the electrode of the battery, or when the separator is formed using a porous substrate such as a nonwoven fabric, a short circuit of the battery due to dendrites is effective. Therefore, the inorganic fine particles used in the polyamine group-containing fine particles and the heat shrinkage suppressing layer are preferably plate-like particles. As will be described later, when the separator is formed by orienting plate-like particles, the path related to ion conduction can be lengthened, so that it is possible to more effectively prevent internal short circuit of the battery due to dendrite.

  As the form of the plate-like particles, it is desirable that the aspect ratio is 5 or more, more preferably 10 or more, and 100 or less, more preferably 50 or less. Further, the average value of the ratio of the length in the major axis direction to the length in the minor axis direction (length in the major axis direction / length in the minor axis direction) of the flat plate surface of the grain is 3 or less, more preferably 2 or less and close to 1. It is desirable to be a value.

  In addition, the average value of the ratio of the long axis direction length and the short axis direction length of the flat plate surface in the plate-like particle can be obtained by image analysis of an image taken with a scanning electron microscope (SEM), for example. it can. Further, the aspect ratio of the plate-like particles can be obtained by image analysis of an image taken by SEM.

  When the polyamine group-containing fine particles or inorganic fine particles are plate-like particles, the average particle diameter is preferably 0.01 μm or more, more preferably 0.1 μm or more, as in the case of other shapes. , Preferably 15 μm or less, and more preferably 5 μm or less. The larger the average particle diameter of the plate-like particles, the greater the effect of suppressing the thermal contraction of the entire separator. However, if this is too large, the thickness of the entire separator increases, which may reduce the energy density of the battery. There is.

  The presence form of the plate-like particles in the separator is preferably such that the flat plate surface is substantially parallel to the surface of the separator. More specifically, the heat shrinkage suppression layer (heat shrinkage suppression layer of the separator also functions). The plate-like particles in the obtained (including a porous layer containing polyamine group-containing fine particles) preferably have an average angle between the flat plate surface and the separator surface of 30 ° or less [most preferably, the average angle is 0 °. That is, the plate-like flat plate surface in the heat shrinkage suppression layer of the separator is parallel to the surface of the separator.

  Further, when the polyamine group-containing fine particles and inorganic fine particles are in the form of secondary particles in which primary particles are continuous (hereinafter simply referred to as “secondary particles”), the secondary particles are entangled with each other in the heat shrinkage suppression layer. Since it exists in such a state, compared with the case where it is a primary particle, it becomes possible to suppress the thermal contraction of the whole separator more effectively. In addition, since the polyamine group-containing fine particles and inorganic fine particles are secondary particles, it is possible to effectively secure the gaps between the particles, and the movement of ions in the battery becomes easier, so the output is particularly high. Therefore, it is possible to configure a battery suitable for use in applications such as automobiles and electric tools.

  The average particle diameter of the secondary particles is a number average particle diameter measured by the same method such as polyamine group-containing fine particles, preferably 0.1 μm or more, more preferably 0.2 μm or more, It is preferably 15 μm or less, and more preferably 5 μm or less. If the average particle diameter of the secondary particles is too large, the thickness of the entire separator may be too large. Moreover, when the average particle diameter of the secondary particles is too small, there is a possibility that the effect of suppressing the thermal contraction of the entire separator is reduced.

  The average particle diameter of the primary particles constituting the secondary particles is preferably 0.01 μm or more, and more preferably 1 μm or less. If the average particle size of the primary particles is too small, the pore size formed by the voids between the particles becomes too small, which may hinder the movement of ions and reduce the battery output. In addition, if the average particle diameter of the primary particles is too large, the number of primary particles forming the secondary particles decreases, the entanglement between the particles decreases, and the heat shrinkage of the entire separator due to the use of the secondary particles. There is a possibility that the suppression effect is reduced.

  Further, the separator of the present invention contains polyamine group-containing fine particles and other fine particles (inorganic fine particles for improving heat resistance, heat-meltable fine particles and heat-swellable fine particles for improving safety), for example, a porous group such as a nonwoven fabric. The material may be contained in the pores of the material, or a layer containing polyamine group-containing fine particles or other fine particles may be formed on the surface of the porous substrate.

  Examples of the constituent material of the porous substrate such as nonwoven fabric include cellulose and its modified products [CMC, hydroxypropyl cellulose (HPC), etc.], polyolefin [polypropylene (PP), propylene copolymer, etc.], polyester [PET , Polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc.], resins such as polyacrylonitrile (PAN), aramid, polyamideimide, polyimide; inorganic oxides such as glass, alumina, zirconia, silica; A porous substrate such as a nonwoven fabric may be formed by using two or more of these constituent materials in combination. Moreover, the porous base material, such as a nonwoven fabric, may contain various known additives (for example, an antioxidant in the case of a resin) as necessary.

  The porosity of the separator of the present invention is preferably 30% or more and preferably 70% or less when the separator is in a dry state. If the porosity of the separator is too small, the movement of ions in the separator may be hindered. If it is too large, the strength of the separator may be reduced.

In addition, the porosity of the separator: P (%) can be calculated by obtaining the sum for each component i using the following equation (11) from the thickness of the separator, the mass per area, and the density of the constituent components.
P = {1- (m / t) / (Σa _i · ρ _i )} × 100 (11)
Here, in the above formula, a _i : ratio of component i when the total mass is 1, ρ _i : density of component i (g / cm ³ ), m: mass per unit area of the separator (g / cm ² ), t: thickness of separator (cm).

  When the separator has a multilayer structure, the porosity of each layer calculated in the same manner as the porosity of the entire separator is preferably 30 to 70%.

  In the separator of the present invention, the air permeability represented by the Gurley value specified in JIS P 8117 is preferably 50 seconds or more, more preferably 100 seconds or more, and 600 seconds or less. Is more preferable, and 300 seconds or less is more preferable. If the Gurley value is too small, lithium dendrite crystals and the like are likely to penetrate, and the effect of suppressing internal short circuit may be reduced. If the Gurley value is too large, the ionic conductivity becomes too low and the internal resistance of the battery increases. As a result, the load characteristics may be deteriorated.

  The separator of the present invention preferably has a maximum pore diameter (hereinafter, simply referred to as “maximum pore diameter”) measured by a bubble point method defined in JIS K3832 that is 0.01 μm or more and 1 μm or less. If the maximum pore size of the separator is too small, the pore size of the separator is too small and the ion permeability is deteriorated, and the internal resistance of the battery may be too high. On the other hand, if the maximum pore size of the separator is too large, the pore size of the separator becomes too large and short-circuiting due to direct contact between the positive electrode and the negative electrode tends to occur, or the effect of suppressing internal short-circuiting due to lithium dendrite crystals is reduced. There is a risk of doing.

  In addition, the Gurley value and the maximum hole diameter of the separator of the present invention can be set to the above values by adopting the configuration described in detail so far.

  The thickness of the separator is preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of securing the strength of the separator and better suppressing, for example, the occurrence of an internal short circuit. However, if the separator is too thick, it is likely to cause a decrease in the energy density of the battery and an increase in internal resistance. Therefore, the thickness of the separator is preferably 40 μm or less, and more preferably 30 μm or less.

  In addition, the separator is composed of a multilayered membrane having a porous membrane mainly composed of polyolefin (such as a microporous membrane made of polyolefin), a porous layer containing polyamine group-containing fine particles, and other heat shrinkage suppression layers. When the thickness of the porous film mainly composed of polyolefin is 10 to 30 μm, the thickness of the porous layer containing the polyamine group-containing fine particles is 1 to 10 μm, and other heat shrinkage suppression layers are provided, It is preferable to adjust the thickness so that the thickness of the separator is 1 to 10 μm, and the thickness of the entire separator becomes the above-mentioned preferable value.

  The separator of the present invention can be produced, for example, by the following methods (I), (II) and (III).

  Production method (I) is a composition (liquid composition such as slurry) in which polyamine group-containing fine particles and, if necessary, a binder, heat-meltable fine particles, heat-swellable fine particles and the like are dispersed in water or a suitable solvent. Is applied to the surface of the electrode (positive electrode and / or negative electrode) used in the battery, and dried to remove the solvent, thereby forming a separator as a porous layer integrated with the electrode. .

  The composition for forming a separator used in the production method (I) includes polyamine group-containing fine particles and, if necessary, binders, heat-meltable fine particles, heat-swellable fine particles, and the like. (The same shall apply hereinafter.) (The binder may be dissolved). The solvent used in the composition for forming the separator may be any one that can uniformly disperse the polyamine group-containing fine particles, the heat-meltable fine particles, and the heat-swellable fine particles, and can uniformly dissolve or disperse the binder. Organic solvents such as aromatic hydrocarbons such as toluene, furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) and various surfactants are used. The interfacial tension can also be controlled by appropriately adding.

  In the separator forming composition, the solid content including polyamine group-containing fine particles, binder, heat-meltable fine particles, heat-swellable fine particles, and the like is preferably 10 to 40% by mass, for example.

  As a method for applying the separator-forming composition to the electrode surface, for example, a coating method using a known coating apparatus such as a blade coater, a roll coater, a die coater, a spray coater, or a gravure coater can be employed. In addition, when plate-like particles are used for the polyamine group-containing fine particles, it is preferable to apply a share to the applied separator-forming composition from the viewpoint of enhancing the orientation of the plate-like particles in the separator. Therefore, when using plate-like particles for the polyamine group-containing fine particles, among the above-mentioned coating apparatuses, a coating apparatus that can apply a share to the separator-forming composition during coating, such as a blade coater or a die coater, is used. It is preferable.

  The separator manufacturing method (II) is the same composition for forming a separator as that used in the manufacturing method (I) for a porous film mainly made of polyolefin (such as a microporous film made of polyolefin) or a porous substrate such as a nonwoven fabric. This is a manufacturing method in which an object is applied or impregnated and then dried at a predetermined temperature.

  In addition, when the porous substrate is a non-woven fabric and the opening diameter of the pores is relatively large (for example, when the opening diameter of the pores is 5 μm or more), this tends to cause a short circuit of the battery. Therefore, in this case, it is preferable to have a structure in which all or part of the polyamine group-containing fine particles, heat-meltable fine particles, heat-swellable fine particles and the like are present in the pores of the nonwoven fabric. By adopting such a structure, the ion conduction path can be lengthened or complicated, and a short circuit of the battery due to dendrites can be prevented more effectively. In order to allow polyamine group-containing fine particles, heat-meltable fine particles, heat-swellable fine particles, etc. to be present in the pores of the nonwoven fabric, for example, after applying or impregnating the nonwoven fabric with a composition for forming a separator, After removing the excess composition through the gap, a process such as drying may be used.

  In addition, when plate-like particles are used for the polyamine group-containing fine particles, it is preferable to apply a share to the separator-forming composition as described above in order to increase the orientation of the plate-like particles in the separator. By applying a certain gap after applying or impregnating the composition for a nonwoven fabric, a share can be applied to the composition for forming a separator.

  In addition, when using a porous membrane mainly composed of polyolefin, such as a polyolefin microporous membrane, as a base material, a heat shrinkage suppression layer (heat shrinkage not containing polyamine group-containing fine particles) is used to suppress the thermal shrinkage of the entire separator. In order to form the suppression layer, for example, the following method can be used. First, a composition for forming a heat shrinkage suppression layer is prepared in the same manner as the composition for forming a separator, except that inorganic fine particles are used instead of the polyamine group-containing fine particles, the heat-meltable fine particles, and the heat-swellable fine particles. Then, heat shrink using a blade coater, roll coater, die coater, spray coater, gravure coater, etc. on the surface opposite to the surface on which the layer containing the polyamine group-containing fine particles is formed, for example A heat shrinkage suppression layer is formed through a step of applying and drying a composition for forming a suppression layer.

  The separator manufacturing method (III) is the same as the separator forming method used in the manufacturing method (I) or manufacturing method (II), applied to the surface of a suitable substrate such as PET, dried and porous. In this method, a film is formed, and the film is peeled off from the substrate to form an independent film separator.

  In addition, the separator of this invention should just contain the polyamine group containing fine particle, and is not necessarily limited to the thing of each structure demonstrated so far.

  The nonaqueous electrolyte battery of the present invention only needs to include the separator of the present invention, and other configurations and structures are employed in conventionally known nonaqueous electrolyte batteries (such as lithium secondary batteries). Various configurations and structures can be applied. Hereinafter, a lithium secondary battery, which is a typical embodiment of the nonaqueous electrolyte battery, will be described as an example.

The positive electrode is not particularly limited as long as it is a positive electrode used in conventionally known nonaqueous electrolyte batteries, that is, a positive electrode containing an active material capable of occluding and releasing Li ions. For example, as the positive electrode active _{material, LiM x Mn 2-x O} 4 ( provided that, M is, Li, B, Mg, Ca , Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Spinel type lithium manganese represented by 0.01 ≦ x ≦ 0.5), which is at least one element selected from the group consisting of Sn, Sb, In, Nb, Mo, W, Y, Ru and Rh composite _{oxides, Li x Mn (1-y} -x) Ni y M z O (2-k) F l ( although, M is, Co, Mg, Al, B , Ti, V, Cr, Fe, Cu, It is at least one element selected from the group consisting of Zn, Zr, Mo, Sn, Ca, Sr, and W, 0.8 ≦ x ≦ 1.2, 0 <y <0.5, 0 ≦ z ≦ 0.5, k + l <1, −0.1 ≦ k ≦ 0.2, 0 ≦ l ≦ 0.1) _{iCo 1-x M x O 2} ( however, M is selected Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, from the group consisting of Sb and Ba Lithium cobalt composite oxide which is at least one element and represented by 0 ≦ x ≦ 0.5), LiNi _1-x M _x O ₂ (where M is Al, Mg, Ti, Zr, Fe, Lithium-nickel composite oxidation, which is at least one element selected from the group consisting of Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba and represented by 0 ≦ x ≦ 0.5) LiM _1-x N _x O ₂ (wherein M is at least one element selected from the group consisting of Fe, Mn and Co, and N is Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, and at least one element selected from the group consisting of b and Ba, such as an olivine-type complex oxide represented by 0 ≦ x ≦ 0.5), and using only one of them Or two or more of them may be used in combination.

  In the battery of the present invention, the metal ion that is eluted from the positive electrode and deposited on the negative electrode causes the battery characteristics to deteriorate or causes a short circuit, in the general formula (1) relating to the polyamine group-containing fine particles of the separator. It can be effectively trapped by the action of the represented polyamine group. Therefore, in the battery of the present invention, when the spinel-type lithium manganese composite oxide, in which Mn is apt to be eluted, is used as the positive electrode active material, the effect is particularly remarkable.

  As the positive electrode, a structure in which a positive electrode mixture layer containing the positive electrode active material, a conductive additive and a binder is formed on one side or both sides of a current collector can be used.

  As the binder for the positive electrode, for example, a fluororesin such as polyvinylidene fluoride (PVDF) is used, and as the conductive additive for the positive electrode, for example, a carbon material such as carbon black is used.

  Further, as the positive electrode current collector, a metal foil such as aluminum, a punching metal, a net, an expanded metal, or the like can be used, but usually an aluminum foil having a thickness of 10 to 30 μm is preferably used.

  The lead portion on the positive electrode side is normally provided by leaving the exposed portion of the current collector without forming the positive electrode mixture layer on a part of the current collector and forming the lead portion at the time of producing the positive electrode. However, the lead portion is not necessarily integrated with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.

The negative electrode is not particularly limited as long as it is a negative electrode used in conventionally known nonaqueous electrolyte batteries, that is, a negative electrode containing an active material capable of occluding and releasing Li ions. For example, carbon that can occlude and release lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers as active materials One type or a mixture of two or more types of system materials is used. In addition, simple compounds containing elements such as Si, Sn, Ge, Bi, Sb, and In, compounds and alloys thereof, lithium-containing nitrides, oxides and other compounds that can be charged and discharged at a low voltage close to lithium metal, or lithium metal Alternatively, a lithium / aluminum alloy, or a Ti oxide represented by Li ₄ Ti ₅ O ₁₂ can also be used as the negative electrode active material. A negative electrode mixture in which a conductive additive (carbon material such as carbon black) or a binder such as PVDF is appropriately added to these negative electrode active materials is finished into a molded body (negative electrode mixture layer) using the current collector as a core material. Or those obtained by laminating the above-mentioned various alloys or lithium metal foils alone or as a negative electrode layer on a current collector.

  When a current collector is used for the negative electrode, a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used as the current collector, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the entire negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 5 μm. Further, the lead portion on the negative electrode side may be formed in the same manner as the lead portion on the positive electrode side.

  The positive electrode and the negative electrode can be used in the form of a laminated body laminated via the separator or a wound electrode body obtained by winding the laminated body. When the separator of the present invention is integrated with the electrode, the surface of either the positive electrode or the negative electrode (the positive electrode mixture layer surface of the positive electrode, the negative electrode mixture layer surface or the negative electrode layer surface of the negative electrode) And may be formed on the surfaces of both the positive electrode and the negative electrode.

In addition, as described above, the nonaqueous electrolyte battery of the present invention can use a solution obtained by dissolving a lithium salt in an organic solvent as the nonaqueous electrolyte. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and hardly causes side reactions such as decomposition in a voltage range used as a battery. For example, inorganic lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ ; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (R _f OSO ₂ ) ₂ [where R _f is a fluoroalkyl group], etc .; Can be used.

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; Chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile Sulfites such as ethylene glycol sulfite; etc., and these should be used as a mixture of two or more. It can be.

  The concentration of the lithium salt in the nonaqueous electrolyte is preferably 0.5 to 1.5 mol / l, and more preferably 0.9 to 1.25 mol / l.

  Examples of the form of the non-aqueous electrolyte battery of the present invention include a tubular shape (such as a square tubular shape or a cylindrical shape) using a steel can or an aluminum can as an outer can. Moreover, it can also be set as the soft package battery which used the laminated film which vapor-deposited the metal as an exterior body.

  The nonaqueous electrolyte battery of the present invention can be applied to the same uses as various uses in which conventionally known nonaqueous electrolyte batteries are used.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention.

  In addition, melting | fusing point (melting temperature) of resin shown in a present Example is the value measured using DSC according to the prescription | regulation of JISK7121. The average particle diameter of each fine particle is the number average particle diameter measured by the above method.

  Furthermore, the measurement of the Gurley value is a value measured using a Gurley type air permeability measuring device in accordance with JIS P 8117. Moreover, the measurement of the pore diameter by the bubble point method is measured using a “CFP-1500AEX type palm porometer” manufactured by PMI according to the provisions of JIS K3832, and the following formula is used using the measured bubble point. (12).

D = 4γ / P _x (12)
In the above formula (13), D: pore diameter (m) by the bubble point method, γ: surface tension (N / m) of the liquid, P _x : pressure at the bubble point (Pa).

<Production of polyamine group-containing fine particles>
Production Example 1
A silane coupling agent solution was prepared by adding 10 g of (3-Trimethoxysilylpropylene) diethylentriamine: 500 g in 500 g of an acetic acid aqueous solution having a concentration of 0.5% by mass and uniformly dissolving the mixture.

  The above silane coupling agent solution was added to a slurry prepared by dispersing 1000 g of inorganic fine particles of alumina (average particle size 0.4 μm) in 500 g of water, and the mixture was treated for 60 minutes while stirring with a three-one motor. The treated inorganic fine particles were filtered off and dried to obtain polyamine group-containing inorganic fine particles (A-1).

  In the general formula (1), the polyamine group in the polyamine group-containing inorganic fine particles (A-1) is n = 2 and R is H. Further, the amount of polyamine groups calculated from the quantification result of Si by ICP emission spectroscopy was 0.09 mmol / g in terms of the amount of NH groups.

Production Example 2
The polyamine group-containing inorganic fine particles (A -2) was produced.

  In the general formula (1), the polyamine group in the polyamine group-containing inorganic fine particles (A-2) is n = 1 and R is H. The amount of polyamine group calculated from the quantitative result of Si by ICP emission spectroscopy was 0.05 mmol / g in terms of the amount of NH group.

Production Example 3
The same procedure as in Production Example 1 except that the silane coupling agent was changed to N- (2-Aminoethyl) -3-aminopropyltrimethylsilane and the inorganic fine particles were changed to 1000 g of plate-like boehmite (average particle size 1 μm, aspect ratio 10). Polyamine group-containing inorganic fine particles (A-3) were produced.

  In the general formula (1), the polyamine group in the polyamine group-containing inorganic fine particles (A-3) is n = 1 and R is H. Further, the amount of polyamine group calculated from the quantification result of Si by ICP emission spectroscopy was 0.07 mmol / g in terms of the amount of NH group.

Production Example 4
10 g of chloromethylstyrene-divinylbenzene copolymer particles (average particle size 0.8 μm), which are organic fine particles, are placed in a solution of 15 g of triethylenetetramine dissolved in 10 g of methanol and 80 g of ion-exchanged water, and at 60 ° C. for 5 hours. Reacted. Thereafter, the reaction product was filtered off, washed with ion exchange water, and dried to obtain polyamine group-containing organic fine particles (B-1).

In the general formula (1), the polyamine group in the polyamine group-containing organic fine particles (B-1) is n = 3 and R is H. The amount of polyamine groups determined by ¹ H-NMR analysis was 4.1 mmol / g in terms of the amount of NH groups.

Production Example 5
Except that the organic fine particles were changed to copolymer particles (average particle diameter 0.4 μm) of glycidyl methacrylate, methyl methacrylate, and trimethylolpropane dimethacrylate, the same as in Production Example 4, polyamine group-containing organic fine particles ( B-2) was produced.

In the general formula (1), the polyamine group in the polyamine group-containing organic fine particles (B-2) is n = 3 and R is H. In addition, the amount of polyamine groups determined by ¹ H-NMR analysis was 4.0 mmol / g in terms of the amount of NH groups.

Example 1
<Production of negative electrode>
A negative electrode active material-containing paste is prepared by mixing 95 parts by mass of graphite as a negative electrode active material and 5 parts by mass of PVDF as a binder with N-methyl-2-pyrrolidone (NMP) as a solvent in a uniform manner. Prepared. This negative electrode mixture-containing paste is intermittently applied on both sides of a 10 μm thick current collector made of copper foil so that the coating length is 320 mm on the front surface and 260 mm on the back surface, dried, and then subjected to a calendar treatment to obtain a total thickness. The thickness of the negative electrode mixture layer was adjusted so that the thickness was 142 μm, and the negative electrode mixture layer was cut to a width of 45 mm to produce a negative electrode having a length of 330 mm and a width of 45 mm. Further, a tab was welded to the exposed portion of the copper foil of the negative electrode to form a lead portion.

<Preparation of positive electrode>
The positive active material LiMn _1.5 Ni _0.5 O ₄ : 85 parts by mass, the conductive auxiliary agent acetylene black: 10 parts by mass, and the binder PVDF: 5 parts by mass using NMP as a solvent. Thus, a positive electrode mixture-containing paste was prepared. This paste is intermittently applied on both sides of a 15 μm thick aluminum foil serving as a current collector so that the coating length is 320 mm on the front surface and 260 mm on the back surface, dried, and then calendered to a total thickness of 150 μm. The thickness of the positive electrode mixture layer was adjusted so that the width was 43 mm, and a positive electrode having a length of 330 mm and a width of 43 mm was produced. Further, a tab was welded to the exposed portion of the aluminum foil of the positive electrode to form a lead portion.

<Preparation of separator>
1000 g of the polyamine group-containing inorganic fine particles (A-1) produced in Production Example 1 are dispersed in 1000 g of water, and 120 g of SBR latex (solid content ratio 40% by mass) is further added as a binder to uniformly disperse the separator. A slurry was prepared.

Thickness after drying using a die coater on one side of a polyolefin microporous membrane (thickness 20 μm, porosity 40%) formed by laminating the slurry in the order of PE layer, PP layer, PE layer Was applied to a thickness of 5 μm and dried to obtain a separator having a total thickness of 25 μm. In addition, the volume ratio of the polyamine group-containing inorganic fine particles (A-1) in the layer containing the polyamine group-containing inorganic fine particles (A-1) of the separator is 87% by volume in the total volume of the constituent components of this layer. is there. The amount of polyamine groups in the separator was 0.5 mmol / m ² in terms of NH groups.

<Battery assembly>
The negative electrode and the positive electrode were overlapped with the separator interposed therebetween, and wound in a spiral shape to produce a wound electrode body. The wound electrode body is crushed into a flat shape and loaded into a battery container, and LiPF ₆ is added to a non-aqueous electrolyte (a solvent in which ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 2 at 1.2 mol / liter). 1) was poured into the battery container and sealed to obtain a lithium secondary battery.

Example 2
A separator was produced in the same manner as in Example 1 except that the polyamine group-containing inorganic fine particles (A-2) produced in Production Example 2 were used instead of the polyamine group-containing inorganic fine particles (A-1). A lithium secondary battery was produced in the same manner as in Example 1 except that was used. The volume ratio of the polyamine group-containing inorganic fine particles (A-2) in the layer containing the polyamine group-containing inorganic fine particles (A-2) of the separator is 87% by volume in the total volume of the constituent components of this layer. is there. The amount of polyamine groups in the separator was 0.3 mmol / m ² in terms of NH groups.

Example 3
A slurry for forming a separator was prepared in the same manner as in Example 1 except that the polyamine group-containing inorganic fine particles (A-3) produced in Production Example 3 were used instead of the polyamine group-containing inorganic fine particles (A-1). .

A PET non-woven fabric (thickness 15 μm, basis weight 8 g / m ² ) was prepared as a substrate, impregnated in the slurry, applied by pulling up through a blade with a gap of 50 μm, and dried. To this, an emulsion of PE fine particles (average particle diameter 1 μm, melting point 135 ° C., solid content ratio 20% by mass) was applied on one side using a die coater and dried to prepare a separator having a total thickness of 25 μm. The volume ratio of the polyamine group-containing inorganic fine particles (A-3) in the layer containing the polyamine group-containing inorganic fine particles (A-3) of the separator is 87% by volume in the total volume of the constituent components of this layer. is there. The amount of polyamine groups in the separator was 0.4 mmol / m ² in terms of NH groups.

  And the lithium secondary battery was produced like Example 1 except having used the said separator.

Example 4
500 g of polyamine group-containing organic fine particles (B-1) produced in Production Example 4 and 100 g of secondary particulate boehmite (average particle size 0.6 μm) are dispersed in 1000 g of water, and a self-crosslinking acrylic resin emulsion as a binder. (Solid content ratio 45% by mass) 100 g was added and uniformly dispersed to prepare a slurry for forming a separator.

  Thickness after drying using a die coater on one side of a polyolefin microporous membrane (thickness 20 μm, porosity 40%) formed by laminating the slurry in the order of PE layer, PP layer, PE layer Was applied to a thickness of 5 μm and dried.

  Next, 1000 g of secondary particulate boehmite (average particle size 0.6 μm) is dispersed in 1000 g of water, and 133 g of a self-crosslinking acrylic resin emulsion (solid content ratio 45 mass%) is further added as a binder to uniformly disperse. Thus, a slurry for forming a heat shrinkage suppression layer was prepared.

A die coater is used on the surface of the polyolefin microporous membrane opposite to the surface on which the layer containing the polyamine group-containing organic fine particles (B-1) is formed. Then, it was applied so that the thickness after drying was 5 μm and dried to obtain a separator having a total thickness of 26 μm. In addition, the volume ratio of the polyamine group-containing organic fine particles (B-1) in the layer containing the polyamine group-containing organic fine particles (B-1) of the separator is 53% by volume in the total volume of the constituent components of this layer. In addition, the volume ratio of the secondary particulate boehmite in the heat shrinkage suppression layer is 87% by volume in the total volume of the constituent components of this layer. The amount of polyamine groups in the separator was 8.2 mmol / m ² in terms of NH groups.

  And the lithium secondary battery was produced like Example 1 except having used the said separator.

Example 5
A separator was produced in the same manner as in Example 4 except that the polyamine group-containing organic fine particles (B-2) produced in Production Example 5 were used in place of the polyamine group-containing organic fine particles (B-1). A lithium secondary battery was produced in the same manner as in Example 1 except that was used. In addition, the volume ratio of the polyamine group-containing organic fine particles (B-2) in the layer containing the polyamine group-containing organic fine particles (B-2) of the separator is 53% by volume in the total volume of the constituent components of this layer. is there. The amount of polyamine groups in the separator was 8.0 mmol / m ² in terms of NH groups.

Comparative Example 1
A lithium secondary battery was produced in the same manner as in Example 1 except that a PE microporous film (thickness 25 μm, porosity 45%) was used as the separator.

Comparative Example 2
A lithium secondary battery was produced in the same manner as in Example 2 except that secondary particulate boehmite (average particle size 0.6 μm) was used instead of the polyamine group-containing inorganic fine particles (B-2).

  The following evaluation was performed about the lithium secondary battery of the Example and the comparative example.

<Charge / discharge test>
About the lithium secondary battery of an Example and a comparative example, after initializing on the following conditions, the charging / discharging test was implemented.

  The battery was initialized by performing constant current charging at a current value of 0.2 C up to a charging voltage of 5.0 V, and then performing constant voltage charging at 5.0 V in a total charging time of 15 hours. After leaving at room temperature for a day, it was carried out by discharging to 3.0 V at a current value of 0.2C.

  Next, the battery was charged under the following conditions to determine the charge capacity and the discharge capacity, and the ratio of the discharge capacity to the charge capacity was evaluated as the charge efficiency. First, constant current charging was performed at a current value of 0.2 C until the battery voltage reached 5.0 V, and then constant current charging at a constant voltage of 5.0 V was performed. The total charging time until the end of charging was 15 hours. The battery after charging was discharged at a discharge current of 0.2 C until the battery voltage reached 3.0V. The batteries of Examples 1 to 5 and Comparative Examples 1 and 2 had a charge / discharge efficiency of almost 100%, and were confirmed to operate normally as batteries.

<High temperature storage characteristics>
About the lithium secondary battery of an Example and a comparative example, the high temperature storage characteristic was evaluated on condition of the following.

  First, constant current charging was performed until the battery voltage reached 5.0 V at a current value of 1 C, and then constant current-constant voltage charging was performed in which constant voltage charging at 5.0 V was performed. The total charging time until the end of charging was 3 hours. Each battery after charging was discharged at a current value of 1 C until the battery voltage reached 3.0 V, and the discharge capacity (capacity before storage) was measured. Next, each battery was charged at a constant current-constant voltage under the same conditions as described above, then left in a constant temperature bath at 85 ° C. for 1 hour, and further allowed to cool to room temperature, and then the battery voltage was 3 at a current value of 1C. Discharge until 0V. About each battery after discharge, constant current-constant voltage charge was further performed under the same conditions as described above, and the discharge capacity (capacity after storage) was measured by discharging until the battery voltage reached 3.0 V at a current value of 1C. . And the ratio of the capacity | capacitance after storage with respect to the capacity | capacitance before storage was calculated | required, and it represented as a percentage, and was taken as the capacity | capacitance maintenance ratio after high temperature storage.

<Heating test>
The lithium batteries of Examples and Comparative Examples were placed in a thermostatic bath, heated from 30 ° C. to 150 ° C. at a rate of 1 ° C. per minute, and heated, and the temperature change of the internal resistance of the battery was determined. The temperature at which the resistance value increased to 5 times or more the value at 30 ° C. was taken as the shutdown temperature. Further, the temperature was raised to 150 ° C. and held for 30 minutes, and changes in the state of each battery were examined.

  The structure of the separator used for the battery of an Example and a comparative example is shown in Table 1, and each said evaluation result is shown in Table 2.

  As shown in Table 2, the batteries of Examples 1 to 5 using the separator containing the polyamine group-containing fine particles were stored at a higher temperature than the batteries of Comparative Examples 1 and 2 using the separator not containing the polyamine group-containing fine particles. Has a high capacity retention rate and good high-temperature storage characteristics.

  In the separators used in the batteries of Examples 1 to 5 and Comparative Examples 1 and 2, the shutdown temperature is in the range of 100 to 150 ° C., and the shutdown is performed in an appropriate temperature range to ensure safety at high temperatures of the battery. It became clear that Moreover, even if it hold | maintained at 150 degreeC after that for all the batteries except the battery of the comparative example 1 for 30 minutes, the abnormality that the surface temperature of a battery rose or the voltage fell was not seen.

On the other hand, it was found that the separator according to the battery of Comparative Example 1 was in a state in which the internal resistance suddenly decreased and an internal short circuit was easily caused by holding at 150 ° C. for 30 minutes. This is presumably because the separator is contracted.

Claims (5)

A separator for use in a nonaqueous electrolyte battery, comprising a polyamine group represented by the following general formula (1), and comprising fine particles having an average particle diameter of 0.01 to 15 μm. Separator for use.
—NH (CH ₂ CH ₂ NH) _n R (1)
[In the general formula (1), n is a positive integer, and R is H or an alkyl group having 1 to 10 carbon atoms. ]   The separator for a nonaqueous electrolyte battery according to claim 1, wherein the fine particles are at least one selected from inorganic fine particles and organic fine particles.   The separator for a non-aqueous electrolyte battery according to claim 1 or 2, wherein the separator is a multilayer porous film having at least a porous film mainly composed of polyolefin and a porous layer containing the fine particles.   The separator for a nonaqueous electrolyte battery according to any one of claims 1 to 3, wherein the separator has a shutdown characteristic in which pores are blocked in a temperature range of 80 to 150 ° C. A non-aqueous electrolyte battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
The said separator is a separator for nonaqueous electrolyte batteries in any one of Claims 1-4, The nonaqueous electrolyte battery characterized by the above-mentioned.