JP2006351386A - Battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery provided having shut-down function in a separator, when temperature in the battery rises abnormally, and free from short-circuiting between a positive electrode and a negative electrode, even if resin is dissolved and liquidized, when the temperature rises higher than the melting point for the resin constituting the separator, and a manufacturing method for the battery. <P>SOLUTION: The battery has the separator provided with ionic conductivity and installed between a pair of electrodes with active substance layers, and a porous insulating layer provided with the ionic conductivity, on at least one of the separator or the electrode. The separator is a porous film constituted of material provided having the melting point in the range of 90 to 160°C, and the porous insulating layer is provided with resistance to heat of higher than 160°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery and a method for manufacturing the same, and in particular, a separator having ion conductivity is disposed between a pair of electrodes having an active material layer, and at least one between the separator and the electrode. The present invention relates to a battery provided with a porous insulating layer having ion conductivity and a method for manufacturing the same.

In recent years, with the development of portable electronic devices, higher capacity and higher output density of batteries used as power sources have been advanced. Lithium ion secondary batteries are attracting attention as batteries that satisfy these requirements. A lithium ion secondary battery has a high voltage and a high energy density, but abnormal heat generation may occur due to an internal short circuit or an external short circuit, and sufficient measures against this problem are required.
In lithium ion secondary batteries currently in practical use, active material powder such as lithium-cobalt composite oxide, electronic conductive powder and binder resin are mixed to form a paste, which is applied onto an aluminum current collector. A polyolefin having a melting point of 90 to 160 ° C. using a paste obtained by mixing a carbon-based active material powder and a binder resin and applying the paste on a copper current collector. A porous film made of a resin is used as a separator. In such a battery, when the battery is abnormally heated, the olefinic resin melts and the micropores in the membrane are blocked, and the ionic conductivity of the separator is lowered, thereby having a shutdown function to block the battery reaction. Yes. However, if the temperature rises further than the melting point of the olefin resin, the resin melts and fluidizes, and the separator itself contracts or a hole is formed in the separator, thereby causing electronic insulation between the positive electrode and the negative electrode. May become insufficient and lead to an internal short circuit.

On the other hand, instead of the polyolefin-based separator, a porous separator excellent in heat resistance, comprising an aggregate of insulating particles such as inorganic oxide having a melting point of 1000 ° C. or higher and a binder resin having a melting point of about 200 ° C. There is a battery used. In such a battery, since the melting point of the porous separator is high, the separator itself does not shrink or cause a hole in the separator, but the separator itself does not have a shutdown function and blocks the battery reaction. Can not do it.
Therefore, a battery using a porous separator excellent in heat resistance and an electrode having an active material layer containing a material having a reaction blocking function or a current blocking function has been proposed (see, for example, Patent Document 1). In such a battery, when the battery is abnormally heated, the reaction of the active material is blocked by coating the surface of the active material, the movement of electrolyte ions is blocked by blocking the ion path, the resistance of the electrode As a result, the flow of electrons in the electrode can be blocked.

JP 2004-327183 A

  However, in a battery including the porous separator having excellent heat resistance and an electrode having an active material layer containing a material having a reaction blocking function or a current blocking function, the porous separator itself does not have a shutdown function. Therefore, there is a problem that the battery reaction cannot be sufficiently blocked when the battery is abnormally heated. On the other hand, in the case of using a porous membrane made of polyolefin resin having a shutdown function as a separator, a technology for preventing a short circuit of the battery due to melting and fluidization of the resin that occurs when the temperature rises further than the melting point of the polyolefin resin. Has not been developed yet.

  The present invention has been made in order to solve the above-described problems. The separator has a shutdown function when the abnormal temperature of the battery rises, and the temperature rises further than the melting point of the resin constituting the separator. An object of the present invention is to provide a battery that does not cause a short circuit of the battery even if it melts and fluidizes, and a battery manufacturing method.

In the present invention, a separator having ion conductivity is disposed between a pair of electrodes having an active material layer, and a porous insulating layer having ion conductivity is disposed on at least one of the separator and the electrodes. In the provided battery, the separator is a porous film made of a material having a melting point of 90 to 160 ° C., and the porous insulating layer has a heat resistance higher than 160 ° C. It is a battery.
In the present invention, a separator having ion conductivity is disposed between a pair of electrodes having an active material layer, and at least one of the separator and the electrode has a porous insulating layer having ion conductivity. In which the active material layer paste containing the active material, the conductive particles and the binder is applied on one current collector to produce one electrode, and the active material and the binder An active material layer paste containing the active material layer surface of at least one of the electrodes, and a porous insulating layer paste containing insulating particles and a binder. A porous material composed of a material having a melting point of 90 to 160 ° C. as a separator between a step of forming a porous insulating layer by applying on the surface and a pair of electrodes disposed so that the active material layer surfaces face each other Sandwich the membrane A method for producing a battery which comprises a non-step.

  According to the present invention, a porous membrane composed of a material having a melting point of 90 to 160 ° C. is used as a separator, and a porous material having a heat resistance higher than 160 ° C. between the separator and at least one electrode. By disposing an insulating layer, the battery reaction can be shut off by the shutdown function of the separator when the abnormal temperature of the battery rises, and the temperature rises further than the melting point of the resin constituting the separator, causing the resin to melt and flow Even if the battery is changed, it is possible to prevent a temperature increase due to the internal combustion runaway of the battery without causing a short circuit of the battery.

FIG. 1 is a cross-sectional view of a battery according to an embodiment of the present invention. In FIG. 1, the battery includes a separator 3, a positive electrode 4 having a positive electrode active material layer 5 and a positive electrode current collector 6, a negative electrode 7 having a negative electrode active material layer 8 and a negative electrode current collector 9, and a separator 3 and a positive electrode 4. A porous insulating layer 11 disposed between the separator 3 and the negative electrode 7 is provided inside the battery container 10. In FIG. 1, the porous insulating layer 11 is disposed between both the separator 3 and the positive electrode 4 and between the separator 3 and the negative electrode 7, but may be disposed on either one. Good. And the separator 3 is a porous film comprised from the material which has 90-160 degreeC melting | fusing point, and the porous insulating layer 11 has heat resistance higher than 160 degreeC. The separator 3 and the porous insulating layer 11 are impregnated with an electrolytic solution.
FIG. 2 is an enlarged cross-sectional view of the porous insulating layer 11. In FIG. 2, the porous insulating layer 11 includes insulating particles 1 and a binder 2.

(Porous insulation layer)
The porous insulating layer 11 in the present embodiment has heat resistance and ion conductivity higher than 160 ° C. In this embodiment, having heat resistance higher than 160 ° C. means that the porous insulating layer 11 is not deformed or melted even at a temperature higher than 160 ° C., and the electronic insulation between the electrodes can be maintained. It also means that ion conductivity is exhibited even in a state where the temperature once rises higher than 160 ° C. and then falls to 100 ° C. or lower.
The higher the temperature at which the heat resistance is maintained, the higher the safety because it is possible to provide a battery with higher safety. However, even if the self-decomposition reaction of the positive electrode active material occurs, it is more practical up to 300 ° C. Specifically, it is preferable that heat resistance can be maintained up to 200 ° C. Specifically, the thermal deformation rate (particularly the heat shrinkage rate) of the porous insulating layer 11 in the temperature range up to 300 ° C., more practically up to 200 ° C., is preferably 5% or less, more preferably 1% or less. There must be. If this thermal deformation rate (particularly the thermal shrinkage rate) is greater than 10%, a short circuit between the positive electrode 4 and the negative electrode 7 tends to occur.

In the present embodiment, the porous insulating layer 11 includes insulating particles 1 and a binder 2.
The insulating particles 1 contained in the porous insulating layer 11 may be any particles that have electronic insulating properties and can stably exist in the battery, and may be inorganic particles or organic particles. .
As inorganic substances, Al ₂ O ₃ (alumina), SiO ₂ (silica), ZrO ₂ (zirconia), CeO ₂ (ceria), Y ₂ O ₃ (yttria), TiO ₂ , La ₂ O ₃ , LiAlO ₂ , Li _{2 O, BeO, B 2 O} 3, Na 2 O, MgO, P 2 O 5, CaO, Cr 2 O 3, inorganic oxides such as _Fe 2 _{O 3} and _{ZnO, Si 3 N 4, BN} , AIN, TiN And inorganic nitrides such as Ba ₃ N ₂ , inorganic carbides such as SiC, ZrC and B ₄ C, inorganic carbonates such as MgCO ₃ and CaCO ₃ , inorganic sulfates such as CaSO ₄ and BaSO ₄ , zeolite, sepiolite and palygorskite And porous composite ceramics.
In addition, as organic substances, fluororesins such as polytetrafluoroethylene, polyether resins such as polyethylene oxide and polypropylene oxide, polymethyl methacrylate, polystyrene, polyacrylonitrile, polyacrylic acid ester, polyimide resin, polyamide resin (aramid), Examples include polyester resin, polycarbonate resin, polyphenylene oxide resin, phenol resin, urea resin, melamine resin, polyurethane resin, epoxy resin, acetal resin, and ABS resin.
These inorganic substances and organic substances can be used alone or in combination of two or more. Among them, ceramics (inorganic oxides and porous composite ceramics) and polyamide resins have melting points higher than 200 ° C. It is more preferable because it does not melt and fluidize when an abnormal temperature rises and does not cause a short circuit. In particular, ceramics selected from alumina, silica, zirconia, ceria, yttria and mixtures thereof are most preferable because they can increase the packing density of the porous insulating layer 11 and further improve the heat resistance.

The average particle diameter of the insulating particles 1 is preferably 0.5 μm or less, more preferably 0.1 μm or less from the viewpoint of suppressing lithium metal growth, and further from the viewpoint of obtaining a current attenuation function. And most preferably 0.03 μm or less.
Furthermore, the shape of the insulating particles 1 is not particularly limited, and may be spherical, elliptical, fibrous, scale-like, or the like. In particular, if a spherical shape is used, the packing density can be increased, so that the porous insulating layer 11 can be thinned. If an elliptical, fibrous, or scaly shape is used, the porous insulating layer 11 The void volume can be increased.

  The binder 2 contained in the porous insulating layer 11 may be any material that can be stably present in the battery. For example, an acrylic polymer, polyacrylonitrile, a polyimide resin and a precursor thereof (such as polyamic acid), Fluororubbers such as polyvinylidene fluoride and polytetrafluoroethylene, polyolefin resins and derivatives thereof, polyether resins such as polyethylene oxide and polypropylene oxide, and copolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene, Rubbers such as polyvinyl alcohol, vinyl acetate, styrene-butadiene copolymer latex and acrylonitrile-butadiene copolymer latex, cellulose derivatives such as ammonium salt of carboxymethyl cellulose, Tomeruto agents and the like which is dissolved in a solvent such as xylene. Among them, those having ion conductivity such as polyethylene oxide can provide excellent ion conductivity by the porous insulating layer 11. In addition, the binder 2 selected from acrylic polymer, polyacrylonitrile, polyimide, polyvinylidene fluoride and derivatives thereof, polyolefin and derivatives thereof, and mixtures thereof has a melting point higher than 160 ° C. and is porous. Since the heat resistance of the insulating layer 11 can be improved, it is more preferable.

The volume ratio of the insulating particles 1 and the binder 2 per unit volume of the porous insulating layer is preferably 0.2 to 0.8. If the volume ratio is smaller than 0.2, the porous insulating layer 11 has too many voids, so that the mechanical strength is weak, and the role as a layer may not be sufficiently achieved. On the other hand, if the volume ratio is greater than 0.8, there are too few voids in the porous insulating layer 11, and thus the ionic conductivity may not be sufficiently maintained. More specifically, by containing 10% to 95% by weight of the insulating particles 1 and 5% to 90% by weight of the binder 2 in the porous insulating layer 11, the above preferred volume ratio and can do.
Further, it contains 50% by weight to 90% by weight of insulating particles 1 and 10% by weight to 50% by weight of binder 2 (the weight ratio of insulating particles 1 and binder 2 is 1: 1 to 9: 1. By forming the porous insulating layer 11, the insulating particles 1 are densely packed to form a skeleton of the layer. Therefore, even when the binder 2 having a melting point of 160 ° C. or less is used, Shape deformation due to heat shrinkage hardly occurs. Further, in the porous insulating layer 11 using the binder 2 having a melting point of 160 ° C. or lower, the binder 2 expands or deforms when the battery is abnormally heated, and the through holes are reduced or blocked. Thus, a current attenuation function for reducing the ion path can be provided.

The method for producing the porous insulating layer 11 is not particularly limited, but a wet method is preferable from the viewpoint of enabling uniform and stable production. Specifically, the porous insulating layer is obtained by applying a paste (solution) in which the insulating particles 1 and the binder 2 are dispersed or dissolved in a solvent on the active material layer of at least one of the electrodes and drying it. 11 is formed. At this time, since the insulating particles 1 and the binder 2 are separated when dried rapidly, the drying temperature is preferably dried slowly at a temperature not higher than the boiling point of the solvent. By using such a method, the porous insulating layer 11 can be produced efficiently.
As the solvent used in the above method, any solvent that can uniformly and stably disperse or dissolve the insulating particles 1 and the binder 2 may be used. For example, N-methylpyrrolidone (NMP) and N, N-dimethylformaldehyde ( DMF). Moreover, when using the water-soluble binder 2, it is also possible to use water and alcohol. Furthermore, an additive may be added to stabilize the paste (solution) in which the insulating particles 1 and the binder 2 are dispersed or dissolved. The additive may be removed by heating or the like, or may remain in the battery as long as it is stably present at high temperature or high voltage and does not inhibit the battery reaction. .
A method for applying the paste (solution) in which the insulating particles 1 and the binder 2 are dispersed or dissolved is not particularly limited, but a method suitable for the desired thickness and application form is preferable. For example, a screen printing method, a bar A coater method, a roll coater method, a reverse coater method, a gravure printing method, a doctor blade method, a die coater method and the like can be used.

The porous insulating layer 11 in the present embodiment may be a single layer or may be laminated with different layers such as materials and constituent material ratios. The thickness of the porous insulating layer 11 is not particularly limited, but is preferably 1 μm to 100 μm, and more preferably 5 μm to 30 μm. Within this range, battery characteristics can be improved while preventing a short circuit between the positive and negative electrodes.
When the pores in the porous insulating layer 11 can be approximated to a sphere, the average diameter of the pores (hereinafter referred to as the pore diameter) is reduced to generate when overcharging or rapid charging is performed. The growth of metallic lithium to be suppressed can be suppressed on the surface of the porous insulating layer 11. Therefore, the average pore diameter in the porous insulating layer 11 is preferably 0.1 μm or less, and more preferably 0.03 μm or less.
The porous insulating layer 11 formed in this way is applied on the active material layer of the electrode, and since the porous insulating layer 11 itself is held by the active material layer, the porous insulating layer 11 flows even when the abnormal temperature of the battery rises. Does not cause a short circuit between the positive and negative electrodes.

  Further, in order to improve the strength of the porous insulating layer 11, the insulation between the positive and negative electrodes, and the ionic conductivity, a substrate may be sandwiched between the porous insulating layer 11 and the active material layer of the positive and negative electrodes. Preferable substrates include electronically insulating porous woven fabrics, nonwoven fabrics, paper, porous membranes and meshes, or granular materials that can stabilize the dimension between positive and negative electrodes. The base material may be any material that is electronically insulating and has a melting point of 160 ° C. or higher. For example, polystyrene, polyacrylonitrile, polymethyl methacrylate, polyacrylic ester, fluororesin (for example, polytetrafluoro Ethylene, polyvinylidene fluoride, etc.), polyamide resin (aramid resin), polyimide resin, polyester resin, polycarbonate resin, polyphenylene oxide resin, phenol resin, melamine resin, polyurethane resin, polyether resin (for example, polyethylene oxide and polypropylene oxide) And resins such as epoxy resin, acetal resin and ABS resin, and inorganic fibers such as glass fiber and alumina fiber. Even a material having a melting point of 160 ° C. or lower, such as polyethylene or polypropylene, can be used as long as the shrinkage rate is less than 10%.

[Separator]
Separator 3 in the present embodiment is ion-conductive and is a porous film made of a material having a melting point of 90 to 160 ° C. As such a porous film, for example, a porous film made of a polyolefin resin such as polyethylene and polypropylene can be mentioned.
In the separator 3 in the present embodiment, when the battery is abnormally heated, the resin melts to close the micropores in the film, and the ionic conductivity of the separator 3 is lowered, thereby blocking the battery reaction.

〔electrode〕
The electrode in this embodiment includes an active material layer and a current collector.
In this embodiment, the active material layer can include an active material, a conductive material, and a binder.
Examples of the active material used for the positive electrode 4 include lithium composite oxides of transition metals such as cobalt, manganese, nickel, and these lithium composite oxides containing various additive elements, copper, iron, chromium, titanium, aluminum, and the like. Lithium composite oxides of these metals and lithium composite oxides containing various additive elements, lithium and vanadium, lithium and molybdenum, lithium and chalcogen, and other composite compounds having various additive elements, polypyrrole , Polyaniline, polydisulfide and the like can be mentioned, and these can be used alone or in combination of two or more. The proportion of the positive electrode active material contained in the active material layer is preferably 50% by weight to 98% by weight, and more preferably 70% by weight to 98% by weight. Moreover, the average particle diameter of the positive electrode active material is preferably 0.05 to 100 μm, and more preferably 0.1 to 30 μm. Within these ranges, the packing density of the active material can be increased and contact with other materials can be improved, so that battery characteristics can be improved.

Examples of the active material used for the negative electrode 7 include carbonaceous materials such as graphitizable carbon, non-graphitizable carbon, natural graphite, artificial graphite, polyacene, V-Sn, Cu-Sn, Fe-Sn, Sn-S _2. In addition, tin-based alloy compounds such as SnO, boron-based oxides, and nitrides such as Li _2.6 Co _0.4 N can be used, and they can be used regardless of chemical characteristics. Among these, a granular thing is used. The proportion of the negative electrode active material contained in the active material layer is preferably 50% by weight to 98% by weight, and more preferably 70% by weight to 98% by weight. Moreover, 0.05-100 micrometers is preferable and, as for the average particle diameter of a negative electrode active material, 0.1-50 micrometers is more preferable. Within these ranges, the packing density of the active material can be increased and contact with other materials can be improved, so that battery characteristics can be improved. Furthermore, metallic lithium can also be used as a negative electrode active material, and this may be either granular or foil-like.

  Moreover, in order to supplement the electroconductivity of said positive electrode active material and negative electrode active material, a conductive support agent can be used together. Examples of the conductive assistant include carbonaceous materials such as acetylene black, ketjen black, and artificial graphite, metal materials, conductive metal compounds, and conductive polymers.

The conductive material used for the electrode preferably includes a PTC (Positive Temperature Coefficient) electronic conductive material having a reaction blocking function at 90 ° C. to 160 ° C. Here, the reaction blocking function is to block the electrode reaction by blocking the electron conduction and / or ionic conduction in the battery. Specifically, the reaction of the electron conductive material is performed at a predetermined temperature. The electron resistivity increases rapidly, blocking the electron conduction, and the electron conductive material particles arranged in close contact with the active material particles soften at a predetermined temperature and coat the active material surface to cause ions and It shows the function of blocking electron conduction.
In the present embodiment, the PTC electronic conductive material is a PTC (hereinafter referred to as a PTC) whose resistance value increases at a predetermined temperature range, particularly in the vicinity of 90 ° C. to 160 ° C., thereby increasing its resistance. , Abbreviated as PTC characteristics). By including this PTC electronic conductive material in the active material layer, when the temperature of the electrode rises to 90 ° C. to 160 ° C., the short-circuit current can be reduced. Although it is preferable from the viewpoint of ensuring safety that the temperature showing this PTC characteristic is 90 ° C. or less, since the resistance value of the electrode increases in the temperature range in which the battery is normally used, the battery performance is deteriorated. Occur. Moreover, when the temperature which shows a PTC characteristic exceeds 160 degreeC, the internal temperature of a battery will rise to this temperature and is unpreferable from a viewpoint of safety. Therefore, it is desirable to design the PTC electronic conductive material so that the temperature showing the PTC characteristic is in the range of 90 ° C. to 160 ° C.

The PTC electronic conductive material in the present embodiment includes a conductive filler and a crystalline resin.
Examples of the conductive filler include carbon materials such as carbon black, graphite, carbon fiber, and metal carbide, and conductive non-oxides such as metal nitride, metal silicide, and metal boride. The proportion of the conductive filler contained in the PTC electronic conductive material is preferably 30% by weight to 80% by weight, and within this range, the conductivity of the electrode can be further improved.
Examples of the crystalline resin include high density polyethylene (melting point: 130 ° C. to 140 ° C.), low density polyethylene (melting point: 110 ° C. to 112 ° C.), polyurethane elastomer (melting point: 140 ° C. to 160 ° C.), polyvinyl chloride ( And a polymer having a melting point of about 145 ° C. The proportion of the crystalline resin contained in the PTC electronic conductive material is preferably 20% by weight to 70% by weight, and within this range, good PTC characteristics can be exhibited while maintaining the conductivity of the electrode. it can.

The method for producing the PTC electronic conductive material is not particularly limited. For example, after a conductive filler and a crystalline resin are kneaded into pellets, the pellets are pulverized by a jet mill device, a ball mill device, or the like. Is mentioned.
The shape of the PTC electronic conductive material is preferably particulate, but may be fibrous or scale-like. When the PTC electronic conductive material is in the form of particles, the average particle size is preferably 0.05 μm to 20 μm, more preferably 0.1 μm to 10 μm. Within this range, the PTC electronic conductive materials can easily form a network, so that the resistance of the electrode during normal operation can be further reduced.
The proportion of the PTC electronic conductive material contained in the active material layer is preferably 0.5 to 15 parts by weight, and 0.7 to 12 parts by weight with respect to 100 parts by weight of the total solid content of the active material layer. Is more preferable. Within this range, the resistance of the electrode during normal operation can be reduced and the discharge capacity of the battery can be increased.

The binder used for the electrode is not particularly limited as long as it can adhere the material constituting the active material layer such as the active material, the conductive material, and the conductive assistant, and can adhere and bond the active material layer and the current collector. Examples thereof include homopolymers or copolymers such as vinylidene fluoride, tetrafluoroethylene, acrylonitrile, ethylene oxide, and styrene-butadiene rubber. In particular, by using a binder having a melting point of 90 ° C. to 160 ° C., the binder is melted in this temperature range, and the adhesion between the materials constituting the active material layer is lowered, so that the resistance of the electrode is increased, and the short circuit is caused. The current can be reduced.
The ratio of the binder contained in the active material layer is preferably 1% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight. If it is in this range, the material which comprises an active material layer can be adhere | attached efficiently.

  In the present embodiment, the current collector may be any metal that is stable in the battery, but it is preferable to use aluminum for the positive electrode 4 and copper for the negative electrode 7. The shape of the current collector can be any shape such as a foil, a net, or an expanded metal. The thickness of the current collector is preferably 5 μm to 100 μm, and more preferably 5 μm to 20 μm. Within this range, the battery can be thinned while maintaining sufficient mechanical strength.

The method for producing the electrode is not particularly limited. For example, an active material layer paste in which an active material, a conductive material, and a binder are dispersed in a dispersion medium is applied on a current collector and dried. A method of forming an active material layer by pressing at a temperature and a predetermined surface pressure, or after applying an active material layer paste on a current collector and drying and pressing at a predetermined surface pressure, The method of heating at temperature etc. is mentioned.
The dispersion medium used in the above method may be any medium that can uniformly and stably disperse the active material, the conductive material, and the binder. Examples thereof include N-methylpyrrolidone (NMP).
The application method of the active material layer paste in which the active material, the conductive material and the binder are dispersed is not particularly limited, but a method suitable for the target thickness and application form is preferable, for example, a screen printing method, a bar coater method, A roll coater method, a reverse coater method, a gravure printing method, a doctor blade method, a die coater method, or the like can be used.

[Electrolyte]
In the present embodiment, the electrolytic solution is not particularly limited. For example, LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ and other electrolytes dissolved in an organic solvent. Examples of organic solvents include ether solvents such as dimethoxyethane and diethyl ether, and ester solvents such as ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (MEC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). Solvent, γ-butyrolactone (GBL), tetrahydrofuran (THF), tetrahydropyran (THP), 1,3-dioxane (DOX), ethyl dimethyl phosphate (EDMP), trimethyl phosphate (TMP), propyl dimethyl phosphate (PDMP) ) And the like, and these can be used alone or in combination of two or more. Furthermore, the electrolyte solution may contain other additives. Examples of combinations of electrolytes include LiPF ₆ / EC + DEC, LiBF ₄ / EC + DEC, LiN (CF ₃ SO ₂ ) ₂ / EC + DEC, LiN (C ₂ F ₅ SO ₂ ) ₂ / EC + DEC, LiPF ₆ / EC + PC, LiPF ₆ / EC + GBL, LiBF ₄ / EC + PC, LiBF ₄ / EC + GBL, LiBF ₄ / EDMP, LiBF ₄ / EC + EDMP, LiN (CF ₃ SO ₂ ) ₂ / EC + GBL, LiN (C ₂ F ₅ SO ₂ ) ₂ / EC + GBL, LiN (CF ₃ SO ₂ ) ₂ / EC + EDMP, LiN (C ₂ F ₅ SO ₂ ) ₂ / EC + EDMP, and the like are exemplified, but not limited thereto. Further, in order to have ionic conductivity even at a high temperature of 100 ° C. or higher, the organic solvent desirably contains a high boiling point solvent such as EC, PC, GBL.

Moreover, electrolyte solution can also be used in gel form. Although the method and material which gelatinize are not specifically limited, The gel which contains electrolyte solution 20weight%-98weight% and the remainder is a polymer component is preferable. When the content of the electrolytic solution is less than 20% by weight, the ionic conductivity of the gel is lowered, and sufficient ionic conductivity cannot be imparted to the separator 3 and the porous insulating layer 11, and the electrolytic solution content is 98% by weight. When it exceeds%, the viscosity of the gel is lowered, and the electrolyte holding ability of the separator 3 and the porous insulating layer 11 may be lowered. The polymer component is not particularly limited, but a methacrylic acid or acrylic acid-based monomer, a polymer having a main chain of a monomer such as alkylene oxide, acrylonitrile, ethylene, styrene, vinyl alcohol, vinyl pyrrolidone, or vinylidene fluoride alone A polymer or a copolymer can be used.
Moreover, it is also possible to use the solid electrolyte which does not contain a liquid instead of an electrolytic solution. Although it does not specifically limit as a solid electrolyte, What is necessary is just a material which has ion conductivity in the operating temperature of a battery. Examples of the polymer solid electrolyte include, for example, polyethylene oxide (PEO) -based, polyacrylonitrile (PAN) -based, polyether-based, polyvinylidene fluoride-based, and polymethylmethacrylate-based mixtures, composites, and copolymers containing a Li salt. Is mentioned. Using a solid electrolyte that does not contain such a liquid has the advantage that, even when the temperature of the battery rises, the pressure inside the battery does not rise.

[Battery container]
In the present embodiment, the battery container 10 is not particularly limited, but a cylindrical or square container made of a metal such as stainless steel or aluminum, or a bag-like or box-shaped container made of a laminate film made of a metal and a resin. It may be. The container made of the laminate film may be any container that can be sealed by heat sealing (heat sealing) and can prevent leakage of the electrolytic solution from the inside of the battery and intrusion of moisture from the outside of the battery. Although a resin film having heat-fusibility can be used for the seal portion, it is preferable to deposit a metal, coat with metal plating, or laminate a metal foil such as aluminum. When a metal foil is used, it can be used alone if it has a sufficient thickness. However, in general, a resin foil laminated to a metal foil with a thickness of several to several tens of microns is used to reduce the weight. It is done. And it is preferable to laminate | stack the polyethylene terephthalate and stretched nylon film for an intensity | strength improvement on the outer surface, and the polyethylene or polypropylene film for providing heat-fusibility.
Various methods can be used for forming the bag-like container. For example, a film cut into a square shape is folded in half and heat-sealed in three directions, and both openings of the film formed in a cylindrical shape are heat-sealed. And the like. The container material may be used as it is cut, but it can also be used after pressing a recess corresponding to the electrode body. Excess container material may be cut or bent after heat sealing.

〔battery〕
In the battery according to the present embodiment, the separator 3 is disposed between the pair of electrodes, and the porous insulating layer 11 may be disposed on at least one of the separator 3 and the electrode. A stacked structure in which a plurality of sheets are stacked, a wound structure in which strip-shaped electrodes are wound, a folded structure in which strip-shaped electrodes are folded while being folded, or a composite structure in which these are combined may be used. In addition, the ion conductivity between the positive and negative electrodes can be improved by slightly reducing the area of the positive electrode 4 with respect to the negative electrode 7 (about 1% to about 10%).
The current collector terminal connected to the current collector portion of the battery is not particularly limited as long as it is a conductive material that is stably present in the battery, but the positive electrode 4 is made of aluminum, and the negative electrode 7 is made of a metal such as nickel and copper. Or what formed the plating metal like nickel plating copper may join to the electrical power collector, and what extracted the electrical power collector part in which the active material is not apply | coated may be used.
EXAMPLES Hereinafter, although an Example demonstrates the detail of this invention, this invention is not limited by these.

[Example 1]
(Preparation of positive electrode)
91 parts by weight of lithium cobaltate (hereinafter abbreviated as LiCoO ₂ ) as a positive electrode active material, 5 parts by weight of acetylene black as a conductive additive, and 4 parts by weight of polyvinylidene fluoride (hereinafter abbreviated as PVdF: manufactured by Kureha Chemical) as a binder A positive electrode active material layer paste was obtained by dispersing in NMP. The positive electrode active material layer paste was applied on one surface of a 20 μm thick aluminum foil serving as a positive electrode current collector with a roll coater, and then dried at 100 ° C. to obtain a sheet having a thickness of about 100 μm. Furthermore, the positive electrode active material layer paste was similarly applied on the other surface of the aluminum foil and dried at 100 ° C. This sheet was pressed by a roll press machine under conditions of a temperature of 20 ° C. and a linear pressure of 2.0 ton / cm ² to obtain a positive electrode having a thickness of about 70 μm. This was cut into a size of 248 mm × 46 mm, the active material layer having an end portion of 10 mm in the longitudinal direction was peeled on both sides, and the foil portion was exposed to form a current collecting portion.

(Preparation of negative electrode)
93 parts by weight of mesophase carbon microbeads (hereinafter abbreviated as MCMB) and 7 parts by weight of PVdF were dispersed in NMP to obtain a negative electrode active material layer paste. This negative electrode active material layer paste was applied on one surface of a 14 μm thick copper foil serving as a negative electrode current collector with a roll coater and then dried at 100 ° C. to obtain a sheet having a thickness of about 100 μm. Furthermore, the negative electrode active material layer paste was similarly applied on the other surface of the copper foil and dried at 100 ° C. This sheet was pressed by a roll press machine under conditions of a temperature of 20 ° C. and a linear pressure of 2.0 ton / cm ² to obtain a negative electrode having a thickness of about 70 μm. This was cut into a size of 262 mm × 50 mm, the active material layer having an end portion of 10 mm in the longitudinal direction was peeled on both sides, and the foil portion was exposed to form a current collecting portion.

(Preparation of porous insulation layer)
40 parts by weight of PVdF and 60 parts by weight of alumina powder (made by Degussa) having an average particle size of about 0.01 μm were dissolved and dispersed in NMP to obtain a porous insulating layer paste. This porous insulating layer paste was applied onto the positive electrode active material layer by a doctor blade method and dried at 60 ° C. to form a porous insulating layer having a thickness of 8 μm on the positive electrode active material layer. Similarly, this porous insulating layer paste was applied onto the negative electrode active material layer to form a 8 μm porous insulating layer on the negative electrode active material layer.
(Preparation of separator)
A polyolefin porous sheet (Asahi Kasei Hypore 9620) cut into a size of 270 mm × 56 mm was used as a separator.

(Preparation of battery)
After sufficiently vacuum-drying each member, the positive electrode and negative electrode on which the porous insulating layer is formed face each other so that the porous insulating layer faces each other, and a separator is sandwiched between them, and then wound from the end. The electrode body was obtained by turning and fixing with a tape. An aluminum plate having a thickness of 0.1 mm with a fusion material attached thereto was joined to the positive electrode current collector of the electrode body by spot welding. Similarly, a nickel plate having a thickness of 0.1 mm to which a fusing material was attached was joined to the negative electrode current collector by spot welding. This is put into an envelope bag made of an aluminum laminate sheet in an envelope shape, and lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) at a concentration of 1 mol / dm ^3. The electrolyte solution thus obtained was poured, vacuum impregnated, and then sealed under reduced pressure by heat fusion to obtain a battery of Example 1.

[Example 2]
In the preparation of the porous insulating layer of Example 1, silica powder having an average particle diameter of about 0.01 μm was used instead of alumina powder having an average particle diameter of about 0.01 μm. A battery of Example 2 was made in the same manner as Example 1 except for the above.
[Example 3]
In the preparation of the porous insulating layer of Example 1 above, 25 parts by weight of PVdF and 75 parts by weight of silicon carbide powder having an average particle diameter of about 0.5 μm were dissolved and dispersed in NMP and used as the porous insulating layer paste. . A battery of Example 3 was made in the same manner as Example 1 except for the above.
[Example 4]
In the preparation of the porous insulating layer of Example 1, the porous insulating layer paste was prepared by dissolving and dispersing 30 parts by weight of polyacrylonitrile and 70 parts by weight of alumina powder having an average particle diameter of about 0.01 μm in pure water. Using. A battery of Example 4 was made in the same manner as Example 1 except for the above.
[Example 5]
In the preparation of the positive electrode of Example 1, 7 parts by weight of the PTC electronic conductive material, 88 parts by weight of lithium cobaltate as the positive electrode active material, 1 part by weight of acetylene black as the conductive additive and 4 parts by weight of PVdF as a binder were used as a dispersion medium. What was dispersed in some N-methylpyrrolidone (hereinafter abbreviated as NMP) was used as the positive electrode active material layer paste. Here, as the PTC electronic conductive material, a PTC electronic conductive material having a characteristic of a volume specific resistance at room temperature of 0.2 Ω · cm and a volume specific resistance at 135 ° C. of 20 Ω · cm (60 parts by weight of carbon black, The fine particles of PTC electronic conductive material having an average particle diameter of 1 μm obtained by pulverizing a pellet of polyethylene kneaded at a ratio of 40 parts by weight with a jet mill device were used. A battery of Example 5 was made in the same manner as Example 1 except for the above.

[Comparative Example 1]
In the preparation of the battery of Example 1, after fully drying each member in vacuum, the positive electrode and the negative electrode face each other so that the porous insulating layer faces each other, and then a polyolefin separator film is sandwiched therebetween. First, an electrode body obtained by winding a stack of a positive electrode and a negative electrode from the end and fixing with a tape was used. A battery of Comparative Example 1 was made in the same manner as Example 1 except for the above.
[Comparative Example 2]
In the preparation of the porous insulating layer of Example 1, the porous insulating layer is not formed on the positive electrode active material and the negative electrode active material layer, and in the preparation of the battery of Example 1, the active material layer faces. As described above, an electrode body obtained by facing a positive electrode and a negative electrode, sandwiching a separator between them, winding them from the end and fixing them with a tape was used. A battery of Comparative Example 2 was made in the same manner as Example 1 except for the above.
[Comparative Example 3]
In the preparation of the porous insulating layer of Example 1, 100 parts by weight of PVdF dissolved and dispersed in NMP was used as the porous insulating layer paste. A battery of Comparative Example 3 was made in the same manner as Example 1 except for the above.
[Comparative Example 4]
In the preparation of the porous insulating layer of Example 1, the porous insulating layer paste was obtained by dissolving and dispersing 40 parts by weight of PVdF and 60 parts by weight of polyethylene powder having an average particle diameter of about 1 μm and a melting point of 130 ° C. in NMP. Used as. A battery of Comparative Example 4 was made in the same manner as Example 1 except for the above.

The battery in the said Example and a comparative example was evaluated using the method shown below. The design discharge capacity of the battery is 560 mA.
(Capacity test)
The battery was charged at a constant current / constant voltage (CC / CV) at room temperature until it reached 4.2 V at 560 mA, and then the discharge capacity when discharged at a current of 560 mA was measured.
(Oven test)
The uncharged battery was transferred into an oven at room temperature, heated to 160 ° C. at 5 ° C./min, and held at that temperature for 60 minutes. Thereafter, the battery was taken out and checked for the presence of a short circuit.
(Overcharge test)
After the CC / CV charge at room temperature until it reached 4.2V at the above 560 mA, the presence or absence of a short circuit of the battery and the temperature change of the battery surface when the CC / CV charge of 1120 mA-12V was performed were measured.
These test results are shown in Table 1, Table 2 and FIG.
Table 1 shows the discharge capacity during the capacity test and the presence or absence of a short circuit of the battery during the oven test for each of the batteries of Examples 1 to 5 and Comparative Examples 1 to 4.

As shown in Table 1, in the batteries of Examples 1 to 5 and Comparative Example 1, since the porous insulating layer was provided on the positive electrode and the negative electrode active material layer, the battery was not short-circuited. On the other hand, in the batteries of Comparative Examples 2 to 4, since there was no porous insulating layer on the positive electrode and the negative electrode active material layer, a short circuit of the battery occurred. Further, in comparison between Example 1 and Comparative Example 2, the battery of Example 1 having a porous insulating layer had a discharge capacity comparable to that of the battery of Comparative Example 2 having no porous insulating layer.
Table 2 shows the presence or absence of a short circuit of the battery and the maximum temperature reached on the battery surface when the batteries of Examples 1 and 5 and Comparative Examples 1 to 4 were subjected to an overcharge test up to 12 V at 1120 mA. Moreover, the temperature profile at the time of an overcharge test is shown in FIG.

As shown in Table 2, the batteries of Examples 1 and 5 were not short-circuited even when overcharged. In the batteries of Examples 1 and 5, when the battery temperature rose, the battery reaction could be blocked by the shutdown function of the separator, so the maximum temperature reached on the battery surface was low. Furthermore, in the battery of Example 5, when the battery temperature rises, the resistance of the PTC electronic conductive material in the positive electrode active material layer increases, and reaches the specified voltage (12 V) at an early stage to decrease the charging current. The maximum temperature reached on the battery surface was lower. On the other hand, although the battery of Comparative Example 1 did not have a short circuit, the battery ignited rapidly, and the maximum temperature reached on the battery surface reached 300 ° C. or higher as shown in FIG. Moreover, as for the battery of Comparative Examples 2-4, as FIG. 3 showed, the battery short-circuited and the battery temperature rose rapidly.
From the above results, the batteries of Examples 1 to 5 can block the battery reaction by the shutdown function of the separator when the abnormal temperature of the battery rises, and the temperature rises further than the melting point of the resin constituting the separator. Even if the resin is melted and fluidized, a short circuit between the positive electrode and the negative electrode is not caused, and an increase in temperature due to internal combustion runaway of the battery can be prevented.

It is sectional drawing of the battery in embodiment of this invention. It is an expanded sectional view of the porous insulating layer in embodiment of this invention. It is a temperature profile at the time of the overcharge test in the batteries of Examples 1 and 5 and Comparative Examples 1 to 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulating particle, 2 Binder, 3 Separator, 4 Positive electrode, 5 Positive electrode active material layer, 6 Positive electrode collector, 7 Negative electrode, 8 Negative electrode active material layer, 9 Negative electrode collector, 10 Battery container, 11 Porous Insulation layer.

Claims (8)

A battery in which a separator having ion conductivity is disposed between a pair of electrodes having an active material layer, and a porous insulating layer having ion conductivity is disposed at least between the separator and the electrodes. In
The separator is a porous film made of a material having a melting point of 90 to 160 ° C., and the porous insulating layer has a heat resistance higher than 160 ° C.   The battery according to claim 1, wherein the porous insulating layer includes insulating particles and a binder.   The battery according to claim 2, wherein the insulating particles are ceramic particles.   The battery according to claim 3, wherein the ceramic particles are selected from alumina, silica, zirconia, ceria, yttria, and a mixture thereof.   5. The binder according to claim 2, wherein the binder is selected from an acrylic polymer, polyacrylonitrile, polyimide, polyvinylidene fluoride and derivatives thereof, polyolefin and derivatives thereof, and a mixture thereof. The battery described in 1.   The battery according to claim 1, wherein the separator is a polyolefin-based porous film.   The battery according to any one of claims 1 to 6, wherein at least one of the active material layers includes an electronic conductive material having a reaction blocking function or a current blocking function at 90 ° C to 160 ° C. A battery in which a separator having ion conductivity is disposed between a pair of electrodes having an active material layer, and a porous insulating layer having ion conductivity is disposed at least between the separator and the electrodes. In the manufacturing method of
Applying an active material layer paste containing an active material, conductive particles and a binder on one current collector to produce one electrode;
Applying an active material layer paste containing an active material and a binder on the other current collector to produce the other electrode;
Applying a porous insulating layer paste containing insulating particles and a binder on the active material layer surface of at least one electrode to form a porous insulating layer;
And a step of sandwiching a porous film made of a material having a melting point of 90 to 160 ° C. as a separator between a pair of electrodes arranged so that the active material layer surfaces face each other. Method.

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