WO2017110842A1

WO2017110842A1 - Nonaqueous secondary battery and method for manufacturing same

Info

Publication number: WO2017110842A1
Application number: PCT/JP2016/088038
Authority: WO
Inventors: 丈主加味根; 岸見　光浩
Original assignee: 日立マクセル株式会社
Priority date: 2015-12-25
Filing date: 2016-12-21
Publication date: 2017-06-29

Abstract

Provided are: a nonaqueous secondary battery which has excellent productivity and reliability; and a method for manufacturing this nonaqueous secondary battery. A nonaqueous secondary battery according to the present invention is characterized by comprising a multilayer electrode body which is obtained by laminating a positive electrode and a negative electrode with a separator being interposed therebetween, and is also characterized in that separators arranged on both sides of the positive electrode and/or the negative electrode respectively have a compression bonded part in at least a part of the peripheral part and are bonded with each other at the compression bonded parts. This nonaqueous secondary battery is able to be manufactured by a manufacturing method according to the present invention, which comprises a step for arranging separators on both sides of a positive electrode and/or a negative electrode and a step for compression bonding at least parts of the peripheral parts of the separators arranged on both sides of the electrode with each other.

Description

Non-aqueous secondary battery and manufacturing method thereof

The present invention relates to a non-aqueous secondary battery excellent in productivity and reliability and a manufacturing method thereof.

Non-aqueous secondary batteries such as lithium ion secondary batteries have high voltage and high capacity, and thus are highly expected for their development.

For non-aqueous secondary batteries, in addition to those using a wound electrode body formed by winding a laminated body in which a positive electrode and a negative electrode are laminated via a separator in a spiral shape, without winding the laminated body, A device using an electrode body (laminated electrode body) having a structure in which a plate-like positive electrode, a negative electrode, and a separator are stacked is also known.

In a non-aqueous secondary battery using the above-described laminated electrode body, the positive electrode, the negative electrode, and the separator are likely to be displaced from each other during the production of the laminated electrode body or the assembly of the battery. When the separator is displaced and the positive electrode and the negative electrode come into contact with each other, a short circuit occurs, and when the positive electrode and the negative electrode are displaced and the area of the opposing portion through the separator between the positive electrode and the negative electrode is reduced, the capacity is reduced. There is a risk of doing. For this reason, in a battery using a laminated electrode body, it is required to suppress misalignment of the positive electrode, the negative electrode, and the separator in the laminated electrode body.

Currently, a technology to avoid such problems is being studied. For example, in Patent Document 1, two separators arranged above and below a positive electrode are joined to each other by thermal welding at their peripheral portions, whereby a positive electrode is formed into a bag-shaped separator formed by two separators. As a housed structure, a technique for suppressing the occurrence of problems due to misalignment between the positive electrode and the negative electrode and the separator has been proposed.

Japanese Patent No. 3380935

By the way, recently, non-aqueous secondary batteries are also applied to applications that are exposed to relatively high temperatures such as in-vehicle applications. Therefore, in a non-aqueous secondary battery, for example, a laminated layer provided with a layer having high heat resistance instead of a polyolefin separator that has been conventionally used so that sufficient functions can be exhibited even when applied to such applications. A heat-resistant separator such as a mold separator or a separator made of a resin having high heat resistance may be used.

However, when such a heat-resistant separator is used, it is difficult to form a bag-like separator by joining the separators in the same manner as in the case of a conventional polyolefin separator. Therefore, in order to avoid the above problem by joining the separators arranged on both sides of the electrode, there is also a demand for development of a technology that can satisfactorily join even when the above heat-resistant separator is used. .

The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous secondary battery excellent in productivity and reliability, and a method for manufacturing the same.

The nonaqueous secondary battery of the present invention that has achieved the above object has a laminated electrode body in which a positive electrode and a negative electrode are laminated via a separator, and at least one of the positive electrode and the negative electrode The separators arranged on both sides of the electrode each have a crimping part at least at a part of the peripheral edge, and are joined to each other at the crimping part.

The method for producing a non-aqueous secondary battery of the present invention is a method for producing a non-aqueous secondary battery having a laminated electrode body in which a positive electrode and a negative electrode are laminated via a separator, the positive electrode and the negative electrode A step of disposing a separator on both sides of at least one of the electrodes, and a step of crimping and joining at least a part of the peripheral edge of the separator disposed on both sides of the electrode.

According to the present invention, it is possible to provide a non-aqueous secondary battery excellent in productivity and reliability and a manufacturing method thereof.

It is a top view which represents typically an example of the separator which concerns on the nonaqueous secondary battery of this invention. It is the II sectional view taken on the line of FIG. It is a top view which represents typically an example of the positive electrode which concerns on the nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the negative electrode which concerns on the nonaqueous secondary battery of this invention. It is a top view which represents typically an example of the non-aqueous secondary battery of this invention. It is the II-II sectional view taken on the line of FIG.

The nonaqueous secondary battery of the present invention has a laminated electrode body in which a positive electrode and a negative electrode are laminated via a separator. The separators disposed on both sides of at least one of the positive electrode and the negative electrode in the laminated electrode body each have a crimp portion on at least a part of the peripheral portion, and are joined to each other at the crimp portion. Yes.

Alignment between the separator and the electrode (positive electrode or negative electrode) disposed therebetween is prevented by disposing the positive electrode or the negative electrode between the separators in which at least a part of the peripheral edge is pressure-bonded and joined to each other. Therefore, in the non-aqueous secondary battery of the present invention, it is possible to suppress the occurrence of a short circuit due to the direct contact between the positive electrode and the negative electrode due to the displacement of the separator in the laminated electrode body. Moreover, in the battery after completion, the deterioration of characteristics due to the short circuit can be suppressed.

Furthermore, in the laminated electrode body, only the portion where the positive electrode and the negative electrode face each other via the separator functions during the battery reaction, and the region not facing the counter electrode cannot participate in the battery reaction. When the area of the opposing part through the separator of a positive electrode and a negative electrode reduces, the problem of the capacity | capacitance of a battery falling also arises. However, when the laminated electrode body is formed in a state in which the positive electrode or the negative electrode is disposed between the separators bonded to each other at least at a part of the peripheral edge, misalignment between the positive electrode and the negative electrode is difficult to occur. It is possible to reduce the incidence of defective products with insufficient capacity at the time of manufacture, and to suppress capacity reduction due to misalignment between the positive electrode and the negative electrode in a completed battery.

The separator joined to at least a part of the peripheral portion according to the non-aqueous secondary battery of the present invention is composed of two or more separators present on both sides of the positive electrode or the negative electrode, and at least one of the peripheral portions. The part has a crimping part for joining these separators.

In the case of a separator made of polyolefin (polyethylene, polypropylene, etc.) that has been conventionally used as a separator for non-aqueous secondary batteries, it is possible to heat-separate the separators at a relatively low temperature. However, in the case of heat-resistant separators such as laminated separators with high heat-resistant layers and separators made of highly heat-resistant resins, heat welding is not easy because the melting point is high, or before melting. Therefore, it is difficult to bond the separators together by heat fusion.

Therefore, in the present invention, when the separators present on both sides of the positive electrode or the negative electrode are joined, both are pressure-bonded. In this case, even if the separators are made of materials that are difficult to heat-seal as described above or cannot be heat-sealable, they are strong enough to accommodate the electrodes and prevent displacement. Both can be joined. Further, when the separators are joined by pressure bonding, the separators can be joined by a simpler operation than the thermal welding even in a case using a separator made of a material capable of thermal welding (polyolefin or the like).

Therefore, according to the present invention, the productivity and reliability of the non-aqueous secondary battery can be improved.

The embodiment to which the present invention is applicable is not limited to the case where one separator is disposed on each side of the electrode, and there are two or more separators disposed on one or both sides of the electrode. The present invention can also be applied to a case where one separator is folded and disposed on both sides of the electrode.

In addition, the separators to be disposed on both surfaces of the electrodes are joined together in advance at least at a part of the peripheral edge by pressure bonding, and then the electrodes are inserted between the opposing separators, whereby the non-aqueous secondary battery of the present invention May be configured.

For the separator according to the non-aqueous secondary battery of the present invention, a polyolefin microporous film or nonwoven fabric generally used as a separator for non-aqueous secondary batteries can be used.

Examples of the polyolefin constituting the separator include polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer.

The polyolefin microporous film or non-woven fabric may have a single-layer structure containing one or more kinds of polyolefins, or a multilayer structure having a plurality of layers containing different types of polyolefins (for example, It may be a two-layer structure in which a PE layer and a PP layer are laminated, or a three-layer structure in which a PP layer is provided on both sides of the PE layer.

In addition, the separator does not have a melting point, that is, a material having a melting temperature of 250 ° C. or higher measured using a differential scanning calorimeter (DSC) in accordance with the provisions of JIS K 7121, It is also possible to use a material containing a heat resistant material such as a material that is thermally decomposed before melting. When using a separator containing such a heat-resistant material, even if the battery is used in an environment where it is exposed to high temperatures, it is possible to suppress the deterioration of battery characteristics and the occurrence of short circuits due to melting of the separator. Thus, a non-aqueous secondary battery having higher heat resistance and suitable for use in a high temperature environment can be obtained.

As the separator containing the heat resistant material, for example, at least one resin (heat resistant resin) selected from the group consisting of polyamide, polyimide, polyamideimide, polyphenylene sulfide, polyester, polyacrylonitrile, aramid, and cellulose is used. What is contained is mentioned, For example, the nonwoven fabric etc. which were comprised with at least 1 sort (s) of these can be illustrated.

Also, a laminated separator in which a heat-resistant porous layer is provided on the above-mentioned polyolefin microporous film or non-woven fabric can be used. When such a laminated separator is used, the separator shrinkage can be suppressed even when the temperature in the battery rises, and a short circuit due to contact between the positive electrode and the negative electrode can be suppressed. When the temperature becomes high, a non-aqueous secondary battery with higher safety can be obtained, which can ensure a shutdown function that closes the pores of the separator by melting the polyolefin.

The heat-resistant porous layer related to the laminated separator can be formed of, for example, a nonwoven fabric composed of the heat-resistant resin exemplified above. Such a laminated separator is made by heat-welding a non-woven fabric made of a heat-resistant resin on one side or both sides of a microporous film made of polyolefin or a non-woven fabric, or by melting a part of the polyolefin, Can be formed.

The laminated separator has a heat-resistant porous layer mainly comprising inorganic particles having a heat-resistant temperature of 250 ° C. or more on one side or both sides of a substrate layer made of a polyolefin microporous film or nonwoven fabric. The formed one is also included. The “heat-resistant temperature is 250 ° C. or higher” in the inorganic particles in the present specification means that deformation such as softening is not observed at least at 250 ° C.

As the inorganic particles to be contained in the heat-resistant porous layer, boehmite, alumina, silica, titanium oxide and the like are preferable, and one or more of these can be used.

In addition, the heat-resistant porous layer includes a binder for binding the inorganic particles to each other or bonding the heat-resistant porous layer and the base material layer (polyolefin microporous film or nonwoven fabric). It is preferable to contain. The binder includes an ethylene-vinyl acetate copolymer (EVA, having a structural unit derived from vinyl acetate of 20 to 35 mol%), an ethylene-acrylic acid copolymer such as an ethylene-ethyl acrylate copolymer, and a fluorine-based rubber. Styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, epoxy resin, etc. Are preferred, and one or more of these can be used.

In the heat-resistant porous layer containing inorganic particles having a heat-resistant temperature of 250 ° C. or higher, the inorganic particles are included as the main component, and the content of the inorganic particles in the heat-resistant porous layer is the heat-resistant porous layer. In the total volume of the components constituting the stratified layer (in the total volume excluding the void portion), it is preferably 50% by volume or more, more preferably 70% by volume or more, and 99% by volume or less. It is more preferable (the remainder may be the above binder).

The thickness of the separator is preferably 500 μm or less, and more preferably 450 μm or less from the viewpoint of suppressing a decrease in the energy density of the battery. However, if the separator is too thin, there is a possibility that the function of preventing a short circuit may be deteriorated. Therefore, the thickness is preferably 10 μm or more, and particularly a separator made of a nonwoven fabric or a heat resistant porous layer made of a nonwoven fabric. In the case of a laminated separator having a thickness of 100 μm or more, more preferably 150 μm or more.

The porosity of the separator is preferably 30% or more and 80% or less, and more preferably 50% or more in the case of a separator made of a nonwoven fabric.

In the non-aqueous secondary battery of the present invention, the separator as described above is disposed on both sides of the electrode, and a crimping part for joining the separators is formed on at least a part of the peripheral part. And either one of a positive electrode and a negative electrode is accommodated between the separators which oppose.

1 and 2 schematically show an example of a separator according to the nonaqueous secondary battery of the present invention. FIG. 1 is a plan view of the separator, and FIG. 2 is a cross-sectional view taken along the line II of FIG.

The separator 30 is formed into a bag-like shape by providing a pressure-bonding portion 31 (indicated by a lattice pattern in the drawing) that joins the

separators

30a and 30b to each other at least at a part of the peripheral edge. It has become. In FIG. 1, the positive electrode is housed in the bag-shaped separator 30, that is, the positive electrode is inserted between the separator 30a and the separator 30b. The mode that the tab part 13 of the positive electrode utilized for electrical connection with another member protrudes is illustrated.

The crimping part 31 that joins the two

separators

30a and 30b can be configured to bend in the thickness direction (vertical direction in the figure) of the

separators

30a and 30b, for example, as shown in FIG. In addition to polyolefin separators that can be welded together by joining two separators together in such a crimping section, the above-mentioned separators made of heat-resistant resin and heat-resistant porous layers can be used. Even if it is difficult or impossible to heat-separate the separators, such as a laminated separator having a separator, the separators are joined to each other with such a strength that the displacement of the electrodes accommodated therein can be suppressed. be able to.

2 can be formed by corrugating, for example.

Specifically, with both sides of the positive electrode or negative electrode sandwiched between two separators, for example, by pressing from above and below with a mold having grooves on the surface, the separators on both sides of the electrodes are Can be bonded by pressure bonding. In consideration of production efficiency, it is possible to bond the separators by pressing the roll sheet with the positive electrode or negative electrode sandwiched between two separators between the rolls with grooves on the surface. is there. The depth of the groove is not particularly limited as long as the separator does not break. The shape and area of the crimping can also be appropriately changed according to the battery shape by changing the shape of the mold used for processing.

The crimping part in the separator may be provided on the whole peripheral part except the part from which the tab part of the electrode accommodated in the separator is pulled out, or may be provided only in a part. Specifically, it is preferable that a portion having a length of 5% or more in the entire length of the outer periphery of the separator is a crimping portion.

Further, the peripheral portion of the separator may be formed with only one continuous long crimping portion, or a plurality of crimping portions may be formed discontinuously as shown in FIG. In addition, as shown in FIG. 1, when a separator is a rectangle (rectangle or square) by planar view, it is preferable that the crimping | compression-bonding part is formed in each of three sides other than the edge | side which pulls out a tab part at least ( However, in the separator 30 shown in FIG. 1, the crimping | compression-bonding part 31 is provided also in the edge | side where the tab part 13 is pulled out. In this case, the crimping | compression-bonding part provided in two adjacent sides may be continued including the corner | angular part between both sides.

For the positive electrode according to the nonaqueous secondary battery of the present invention, for example, one having a structure having a positive electrode mixture layer containing a positive electrode active material, a binder, a conductive additive and the like on one side or both sides of a current collector is used. The

There is no restriction | limiting in particular about the positive electrode active material which concerns on a positive mix layer, What is necessary is just to use the active material generally used as a positive electrode for nonaqueous secondary batteries, such as a lithium containing transition metal oxide. Specific examples of the lithium-containing transition metal oxide include, for example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x MnO ₂ , Li _x Co _y Ni _1-y O ₂ , Li _x Mny _y Ni _z Co _{1-y. -Z} O ₂ , Li _x Mn ₂ O _{4 and the} like are exemplified (in the above structural formulas, 0 ≦ x ≦ 1.1, 0 <y <1, 0 <z <1). .

As the binder related to the positive electrode mixture layer, the same binder as that used in the positive electrode mixture layer related to the positive electrode for a known non-aqueous secondary battery can be used. Specifically, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyamideimide (PAI), polyimide (PI), acrylic, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC) and the like are preferable. It is mentioned as a thing.

Examples of the conductive aid for the positive electrode mixture layer include graphite such as natural graphite (eg, scaly graphite) and artificial graphite; carbon such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. -Bon black; carbon fiber;

For the positive electrode, for example, a positive electrode active material, a binder and a conductive additive are dispersed in a solvent such as an organic solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture-containing composition (however, the binder May be dissolved in a solvent), and may be produced by a method of forming a positive electrode mixture layer by applying this to one or both sides of a current collector and drying it. Moreover, you may perform a calendar process as needed after formation of a positive mix layer.

As the current collector for the positive electrode, the same one used for the positive electrode of a conventionally known non-aqueous secondary battery can be used, and for example, an aluminum foil having a thickness of 10 to 30 μm is preferable.

The thickness of the positive electrode mixture layer (the thickness per side when the positive electrode mixture layer is formed on both sides of the current collector) is preferably 30 to 95 μm. In the positive electrode mixture layer, the content of the positive electrode active material is preferably 85 to 98% by mass, the content of the binder is preferably 1 to 10% by mass, and the content of the conductive auxiliary agent is It is preferably 1 to 10% by mass.

For the negative electrode according to the non-aqueous secondary battery of the present invention, for example, a negative electrode mixture layer containing a negative electrode active material, a binder or the like is used on one side or both sides of a current collector.

As the negative electrode active material, a conventionally known negative electrode active material used for a negative electrode of a non-aqueous secondary battery, that is, an active material capable of occluding and releasing Li ions can be used. Specific examples of such a negative electrode active material include, for example, graphite (natural graphite; artificial graphite obtained by graphitizing graphitized carbon such as pyrolytic carbons, mesophase carbon microbeads, and carbon fibers at 2800 ° C. or higher; ), Pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesophase carbon microbeads, carbon fibers, activated carbon, and other carbon materials; metals that can be alloyed with lithium (Si, Sn, etc.) And particles containing these metals (alloys, oxides, etc.). In the negative electrode, only one type of the above illustrated negative electrode active materials may be used, or two or more types may be used in combination.

As the binder related to the negative electrode mixture layer, the same binders as those exemplified above as those that can be used for the positive electrode mixture layer can be used. Moreover, when making a negative electrode mixture layer contain a conductive support agent, the same thing as the various conductive support agents illustrated previously as what can be used for a positive mix layer can be used for the conductive support agent.

The negative electrode having the negative electrode mixture layer includes, for example, a negative electrode active material and a binder, and a paste-like or slurry-like negative electrode mixture in which a conductive auxiliary agent is dispersed in an organic solvent such as NMP or a solvent such as water as necessary. It can be produced by preparing a containing composition (however, the binder may be dissolved in a solvent), applying this to one or both sides of the current collector and drying to form a negative electrode mixture layer. . Moreover, you may perform a calendar process as needed after formation of a negative mix layer.

The thickness of the negative electrode mixture layer is preferably, for example, 10 to 100 μm per one side of the current collector. As the composition of the negative electrode mixture layer, for example, the amount of the negative electrode active material is preferably 85 to 99% by mass, and the amount of the binder is preferably 1.0 to 10% by mass. Further, when the conductive additive is contained in the negative electrode mixture layer, the amount of the conductive auxiliary in the negative electrode mixture layer is preferably 0.5 to 10% by mass.

The negative electrode current collector may be made of copper, copper alloy, nickel, nickel alloy foil, punching metal, net, expanded metal, or the like, but copper foil is usually used. The thickness of the negative electrode current collector is preferably 5 to 30 μm, for example.

In the non-aqueous secondary battery of the present invention, a laminated electrode body configured using a positive electrode, a negative electrode, and at least a part of the peripheral edge are bonded to each other and bonded, for example, a bag-shaped separator is used. However, in this laminated electrode body, a positive electrode or a negative electrode may be arranged between separators bonded to each other by pressure bonding depending on the laminated configuration.

There are no particular limitations on the planar shape of the electrodes (positive electrode and negative electrode) according to the non-aqueous secondary battery of the present invention, depending on the shape of the exterior body to be employed, such as a circle or a polygon (such as a square, a pentagon, or a hexagon). Any shape is acceptable, and the planar shape of the bag-shaped separator that accommodates this electrode is also the planar shape of the electrode that accommodates it, such as a circle or a polygon (such as a square, pentagon, or hexagon shown in FIG. 1). Depending on the shape, any shape may be adopted.

The above-mentioned laminated electrode body is enclosed in an exterior body together with a non-aqueous electrolyte solution to obtain the non-aqueous secondary battery of the present invention. For the exterior body, one having a form suitable for accommodating the laminated electrode body can be used. For example, a flat exterior can (including coin shape and button shape), a square exterior can, a metal laminate film exterior body Etc. can be used.

In the non-aqueous electrolyte solution according to the non-aqueous secondary battery of the present invention, a solution containing a lithium salt and an organic solvent and in which the lithium salt is dissolved in the organic solvent is used.

Examples of the lithium salt include inorganic lithium salts such as LiClO ₄ , LiBF ₄ , LiAsF ₆ , and LiSbF ₆ ; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), LiN (FSO ₂ ) ₂ [LiFSI], LiN (CF ₃ SO ₂ ) ₂ [LiTFSI], LiN (C ₂ F ₅ SO ₂ ) ₂ , One or more of organic lithium salts such as lithium bisoxalate borate (LiBOB) can be used.

Examples of organic solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; γ-butyrolactone, substituted at the α-position Cyclic esters such as lactones having a group; chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; acetonitrile, pro Nitriles such as pionitrile and methoxypropionitrile; sulfites such as ethylene glycol sulfite; and the like. It can also be used as a mixture. In order to obtain a battery having better characteristics, it is desirable to use a combination that can obtain a high conductivity, such as a mixed solvent of the above-mentioned cyclic carbonate and the above-mentioned chain carbonate.

It is also preferable to use lactones having a substituent at the α-position as the organic solvent. Since the lactone having a substituent at the α-position has a high boiling point of 150 ° C. or higher, it is difficult to volatilize even when the battery is placed in a high temperature environment, and the composition of the non-aqueous electrolyte changes and the outer body swells. Therefore, a battery having higher heat resistance and excellent storage characteristics at high temperatures can be configured.

In addition to lactones having a substituent at the α-position, high-boiling solvents having a boiling point of 150 ° C. or higher are known, but generally high-boiling solvents have low permeability to polyolefin separators, In order to increase the permeability of the non-aqueous electrolyte to the separator, it is necessary to use another solvent (generally having a low boiling point). On the other hand, since lactones having a substituent at the α-position have good permeability to polyolefin separators, by using a non-aqueous electrolyte using this, for example, without impairing the load characteristics of the battery, Heat resistance can be improved.

The lactone having a substituent at the α-position is preferably, for example, a 5-membered ring (having 4 carbon atoms constituting the ring). The α-position substituent of the lactone may be one or two.

Examples of the substituent include a hydrocarbon group and a halogen group (fluoro group, chloro group, bromo group, iodo group) and the like. As a hydrocarbon group, an alkyl group, an aryl group, etc. are preferable, and it is preferable that the carbon number is 1 or more and 15 or less (more preferably 6 or less). When the substituent is a hydrocarbon group, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, and the like are more preferable.

Specific examples of lactones having a substituent at the α-position include α-methyl-γ-butyrolactone, α-ethyl-γ-butyrolactone, α-propyl-γ-butyrolactone, α-butyl-γ-butyrolactone, α-phenyl -Γ-butyrolactone, α-fluoro-γ-butyrolactone, α-chloro-γ-butyrolactone, α-bromo-γ-butyrolactone, α-iodo-γ-butyrolactone, α, α-dimethyl-γ-butyrolactone, α, α -Diethyl-γ-butyrolactone, α, α-diphenyl-γ-butyrolactone, α-ethyl-α-methyl-γ-butyrolactone, α-methyl-α-phenyl-γ-butyrolactone, α, α-difluoro-γ-butyrolactone , Α, α-dichloro-γ-butyrolactone, α, α-dibromo-γ-butyrolactone, α, α-diiodo-γ-butyrolactone Tons, and the like, it may be used only one of these may be used in combination of two or more. Among these, α-methyl-γ-butyrolactone is more preferable.

When lactones having a substituent at the α-position are used in the organic solvent, only lactones having a substituent at the α-position may be used, but when other organic solvents are used together, 150 ° C or higher It is preferable to use a high-boiling solvent having a boiling point (ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane, trimethyl phosphate, triethyl phosphate, etc.).

When the lactone having a substituent at the α-position is used as the organic solvent, the ratio in the total organic solvent in the non-aqueous electrolyte is preferably 70 to 100% by volume.

The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.6 to 1.8 mol / L, and more preferably 0.9 to 1.6 mol / L.

In addition, for the purpose of improving characteristics such as battery safety, charge / discharge cycleability, and high-temperature storage stability, vinylene carbonates, 1,3-propane sultone, diphenyl disulfide, biphenyl, fluorobenzene are added to the non-aqueous electrolyte. Additives such as t-butylbenzene and halogen-substituted cyclic carbonates (4-fluoro-1,3-dioxolan-2-one etc.) can also be added as appropriate.

Furthermore, in the non-aqueous secondary battery of the present invention, a gel (gel electrolyte) obtained by adding a gelling agent such as a known polymer to the non-aqueous electrolyte may be used.

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

Example 1
<Preparation of positive electrode>
LiNi _0.5 Co _0.2 Mn _0.3 O _{2 as} a positive electrode active material: 96.5 parts by mass, NMP solution containing PVDF as a binder at a concentration of 10% by mass: 20 parts by mass, and a conductive additive Acetylene black: 1.5 parts by mass was kneaded using a biaxial kneader, and NMP was added to adjust the viscosity to prepare a positive electrode mixture-containing paste. This paste is applied to both sides of an aluminum foil having a thickness of 15 μm, vacuum-dried at 120 ° C. for 12 hours, a positive electrode mixture layer is formed on both sides of the aluminum foil, and press treatment is performed. By cutting, a belt-like positive electrode was obtained. When applying the positive electrode mixture-containing paste to the aluminum foil, a part of the aluminum foil was exposed, and the part of the surface that was the application part was also the application part. The thickness of the positive electrode mixture layer of the obtained positive electrode (thickness per one side of the aluminum foil as the positive electrode current collector) was 41 μm.

In order to make the strip-shaped positive electrode into a tab portion, a part of the exposed portion of the aluminum foil (positive electrode current collector) protrudes, and a portion where the positive electrode mixture layer is formed has a substantially rectangular shape with curved corners. Thus, a positive electrode for a battery having a positive electrode mixture layer on both surfaces of the positive electrode current collector was obtained. FIG. 3 is a plan view schematically showing the battery positive electrode (however, in order to facilitate understanding of the structure of the positive electrode, the size of the positive electrode shown in FIG. 3 does not necessarily match the actual one). Not) The positive electrode 10 has a tab portion 13 punched out so that a part of the exposed portion of the positive electrode current collector 12 protrudes, and the shape of the forming portion of the positive electrode mixture layer 11 is a substantially rectangular shape with four corners curved. In the figure, the lengths a, b and c were 61 mm, 137 mm and 10 mm, respectively.

<Production of negative electrode>
The negative electrode active material: 96 parts by mass of soft carbon, acrylic resin: 2 parts by mass, CMC: 2 parts by mass, and water were mixed to prepare a negative electrode mixture-containing paste. The negative electrode mixture-containing paste is applied to both sides of a copper foil having a thickness of 10 μm and dried to form a negative electrode mixture layer on both sides of the copper foil, and press treatment is performed to set the density of the negative electrode mixture layer to 1. After adjusting to 00 g / cm ³ , it was cut to a predetermined size to obtain a strip-shaped negative electrode. In addition, when apply | coating the negative mix containing paste to copper foil, a part of copper foil was exposed and the back surface also made the application part the part made into the application part on the surface. The thickness of the negative electrode mixture layer of the obtained negative electrode (thickness per one side of the copper foil as the negative electrode current collector) was 61.5 μm.

In order to make the strip-shaped negative electrode into a tab portion, a part of the exposed portion of the copper foil (negative electrode current collector) protrudes, and the negative electrode mixture layer forming portion has a substantially square shape with four corners curved. Then, a negative electrode for a battery having a negative electrode mixture layer on both surfaces of the negative electrode current collector was obtained. FIG. 4 is a plan view schematically showing the battery negative electrode (however, in order to facilitate understanding of the structure of the negative electrode, the size of the negative electrode shown in FIG. 4 does not necessarily match the actual one). Not) The negative electrode 20 has a shape having a tab portion 23 punched out so that a part of the exposed portion of the negative electrode current collector 22 protrudes, and the shape of the forming portion of the negative electrode mixture layer 21 is a substantially rectangular shape with four corners curved. In the drawing, the lengths d, e, and f were 64 mm, 142.5 mm, and 10 mm, respectively.

<Production of bag-shaped separator>
Polyimide non-woven fabric (no melting point of polyimide, thickness: 15 μm, porosity: 31%) is cut into a width of 65 mm and a height of 142.5 mm, two sheets are overlapped, and the peripheral portion shown in FIG. 1 (9 locations) ) Was pressure-bonded (corrugated) with a “needleless stapler (trade name)” manufactured by KOKUYO to produce a bag-shaped separator. In this bag-shaped separator, the length of one crimping part was set to 10 mm, and the total ratio of the lengths of the crimping parts formed in the entire length of the outer periphery was 19%. The area of the separator was 107% in the width direction and 104% in the height direction with respect to the area of the positive electrode.

<Battery assembly>
A laminated electrode body was formed using 18 positive electrodes for a battery in which a positive electrode mixture layer was formed on both sides of the positive electrode current collector and 19 negative electrodes for a battery in which a negative electrode mixture layer was formed on both sides of the negative electrode current collector. In the laminated electrode body, all the battery positive electrodes were housed in the bag-shaped separator. Then, the upper and lower ends are set as battery negative electrodes, the battery positive electrodes and the battery negative electrodes are alternately arranged between them, and the tab portions between the positive electrodes and the tab portions between the negative electrodes are welded respectively to form a laminated electrode body. Produced. Further, the laminated electrode body is inserted into the depression of an aluminum laminate film having a thickness of 5.7 mm, a width of 78 mm, and a height of 161 mm in which a depression is formed so that the laminated electrode body can be accommodated. An aluminum laminate film of the same size was placed and three sides of both aluminum laminate films were heat-welded. Then, from the remaining one side of both aluminum laminate films, LiPF ₆ was dissolved at a concentration of 1 mol / l in a non-aqueous electrolyte (a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7), and vinylene carbonate was further added. The solution added in an amount of 2% by mass) was injected. Thereafter, the remaining one side of both aluminum laminate films was vacuum heat sealed to produce a non-aqueous secondary battery having the cross-sectional structure shown in FIG. 6 with the appearance shown in FIG.

Here, FIG. 5 and FIG. 6 will be described. FIG. 5 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 6 is a cross-sectional view taken along the line II-II in FIG. The nonaqueous secondary battery 100 includes a laminated electrode body 102 constituted by laminating a positive electrode and a negative electrode with a separator in an aluminum laminated film outer package 101 constituted by two aluminum laminated films, and a nonaqueous electrolytic solution. (Not shown) is housed, and the aluminum laminate film outer package 101 is sealed by heat-sealing the upper and lower aluminum laminate films at the outer peripheral portion thereof. In FIG. 6, in order to avoid the complexity of the drawing, the layers constituting the aluminum laminate film outer package 101 and the positive electrode, the negative electrode, and the separator constituting the laminated electrode body are not shown separately. .

Each positive electrode of the laminated electrode body 102 is integrated by welding the tab portions together, and the integrated product of the welded tab portions is connected to the positive electrode external terminal 103 in the battery 100, although not shown. The negative electrodes of the laminated electrode body 102 are also integrated by welding the tab portions together, and the integrated product of the welded tab portions is connected to the negative electrode external terminal 104 in the battery 100. The positive electrode external terminal 103 and the negative electrode external terminal 104 are drawn out to the outside of the aluminum laminate film exterior body 101 so that they can be connected to an external device or the like.

Example 2
A bag-like separator was produced in the same manner as in Example 1 except that paper (that is, a cellulose nonwoven fabric, no melting point of cellulose, and a thickness of 20 μm) was used instead of the polyimide nonwoven fabric. And the non-aqueous secondary battery was produced like Example 1 except having used this bag-shaped separator.

Example 3
Instead of polyimide non-woven fabric, a laminate with a three-layer structure having layers made of an aramid non-woven fabric on both sides of a PE microporous film [PE melting point: 130 ° C., PE microporous film thickness: 16 μm, aramid melting point None, the thickness of the layer made of an aramid nonwoven fabric (one side): 3 μm, the total thickness of the laminate: 22 μm, the porosity of the laminate: 50%], and the bag-like separator as in Example 1. Was made. And the non-aqueous secondary battery was produced like Example 1 except having used this bag-shaped separator.

Example 4
Instead of polyimide non-woven fabric, a laminate (PE melting point: 130 ° C., PE) having a heat-resistant porous layer containing 97% by volume of boehmite on one side of the PE microporous film (the remainder being an acrylic resin as a binder) The bag was made in the same manner as in Example 1 except that the thickness of the microporous film made was 16 μm, the thickness of the heat-resistant porous layer was 5 μm, the total thickness of the laminate: 21 μm, and the porosity of the laminate: 45%. A shaped separator was prepared. And the non-aqueous secondary battery was produced like Example 1 except having used this bag-shaped separator.

Example 5
The non-aqueous electrolyte was mixed with propylene carbonate and α-methyl-γ-butyrolactone in a 3: 7 volume ratio, LiBF ₄ at a concentration of 1 mol / L, and LiBOB at a concentration of 0.03 mol / L. A non-aqueous secondary battery was produced in the same manner as in Example 2 except that each was dissolved and further changed to a solution in which vinylene carbonate was added in an amount of 5% by mass.

Example 6
2. Olivine type lithium iron phosphate as a positive electrode active material (average particle size 13 μm): 89 parts by mass, acetylene black as a conductive auxiliary agent: 3.5 parts by mass and 1.5 parts by mass of graphite, acrylic resin: 3. 3 parts by mass, polyvinylpyrrolidone (dispersing agent): 0.3 parts by mass, CMC (thickening agent): 2.4 parts by mass, and using a positive electrode mixture-containing paste prepared by mixing water Produced a positive electrode for a battery in the same manner as in Example 1. The thickness of the positive electrode mixture layer (thickness per one surface) of the obtained positive electrode was 65 μm.

Further, LiBF ₄ was dissolved at a concentration of 1 mol / L and LiBOB at a concentration of 0.03 mol / L in a mixed solvent of propylene carbonate and α-methyl-γ-butyrolactone at a volume ratio of 3: 7, Further, vinylene carbonate was added in an amount of 2.5% by mass to prepare a nonaqueous electrolytic solution.

A nonaqueous secondary battery was produced in the same manner as in Example 2 except that the battery positive electrode and the nonaqueous electrolyte were used.

Example 7
A non-aqueous secondary battery was produced in the same manner as in Example 2 except that the same positive electrode as that produced in Example 6 was used.

Example 8
A bag-like separator was prepared in the same manner as in Example 1 except that a PE microporous film (PE melting point: 130 ° C., thickness: 18 μm) was used instead of the polyimide nonwoven fabric. And the non-aqueous secondary battery was produced like Example 1 except having used this bag-shaped separator.

Comparative Example 1
A laminated electrode body was produced in the same manner as in Example 2 except that the cellulose nonwoven fabric was not formed into a bag shape and was interposed between the positive electrode and the negative electrode as a separator. And the non-aqueous secondary battery was produced like Example 6 except having used this laminated electrode body.

Comparative Example 2
A laminated electrode body was produced in the same manner as in Example 2 except that the cellulose nonwoven fabric was not formed into a bag shape and was interposed between the positive electrode and the negative electrode as a separator. And the non-aqueous secondary battery was produced like Example 2 except having used this laminated electrode body.

Reference Example A bag-like separator was produced in the same manner as in Example 8 except that two PE microporous films were joined by heat welding. And the non-aqueous secondary battery was produced like Example 8 except having used this bag-shaped separator.

Each of 100 non-aqueous secondary batteries of Examples 1 to 5 and 8, Comparative Example and Reference Example was charged at a constant current until the voltage reached 4.2 V at a current value of 300 mA in an environment of 25 ° C. Then, after constant voltage charging at 4.2 V until the current value reached 60 mA, constant current discharge was performed until the voltage reached 2.0 V at a current value of 3000 mA, and the discharge capacity (initial discharge capacity) was measured.

For Examples 6 and 7, each of 100 non-aqueous secondary batteries was charged at a constant current until the voltage reached 3.85 V at a current value of 300 mA in an environment of 25 ° C., and then the current value was reduced to 60 mA. After being charged at a constant voltage of 3.85 V until the voltage reached, a constant current discharge was performed until the voltage became 2.0 V at a current value of 3000 mA, and the discharge capacity (initial discharge capacity) was measured.

Then, a battery in which the initial discharge capacity does not satisfy 96% of the design capacity (3300 mAh) was defined as a defective product, and the occurrence rate of defective products was examined for each example, comparative example, and reference example. These results are shown in Table 1 together with the configuration of the separator used in the battery. In Table 1, in the column of “form (joining)”, when a bag-like separator is used, “bag-like” is described, and the joining means of the two separators when the bag-like separator is used is parenthesized. If the separator is used as it is without being formed into a bag, it is described as “sheet”.

As shown in Table 1, the non-aqueous secondary batteries of Examples 1 to 8 using a bag-shaped separator having a crimping part for joining two separators are the batteries of reference examples (two sheets) corresponding to conventional products. Comparative Example 1 using a non-bag-like separator, whereas the generation of defective products was not observed, as in the case of a battery using a bag-like separator formed by thermally welding a PE microporous film, In the battery of 2, a defective product with insufficient discharge capacity was generated. Therefore, it was found that the batteries of Examples 1 to 8 were superior in productivity and reliability to the batteries of Comparative Examples 1 and 2. Further, the bag-shaped separator used in the batteries of Examples 1 to 8 can be produced by a simpler operation than the separator according to the battery of the reference example in which two PE microporous films are formed into a bag shape by heat welding. Therefore, it can be said that the batteries of Examples 1 to 8 are more productive than the battery of the reference example.

Further, the following non-aqueous secondary batteries of Examples 1 to 8 and Reference Example were subjected to the following high-temperature storage tests 1 and 2 and high-temperature charge / discharge cycle characteristics evaluation.

<High temperature storage test 1>
About each battery, after performing constant current charge and constant voltage charge on the same conditions as the time of first time discharge capacity measurement, it stored for 48 hours in a 100 degreeC thermostat. After each battery is taken out of the thermostat and cooled to room temperature, constant current discharge is performed under the same conditions as the initial discharge capacity measurement, and constant current charge and constant voltage charge are performed under the same conditions as the initial discharge capacity measurement. Then, a constant current discharge was performed, and a discharge capacity (recovery capacity) was measured. And about each battery, the value which remove | divided the said recovery capacity | capacitance by the first time discharge capacity was represented by percentage, and the capacity | capacitance maintenance factor was calculated | required.

<High temperature storage test 2>
About each battery, the recovery capacity | capacitance was measured on the same conditions as the high temperature storage test 1 except having changed the temperature of the thermostat at the time of storage into 135 degreeC. And about each battery, the value which remove | divided the said recovery capacity | capacitance by the first time discharge capacity was represented by percentage, and the capacity | capacitance maintenance factor was calculated | required.

<High-temperature charge / discharge cycle characteristics evaluation>
Each of the batteries of Examples 1 to 5, 8 and Reference Example was charged at a constant current until the voltage reached 4.2 V at a current value of 30 A in an environment of 50 ° C., and the discharge capacity was 1. A constant current discharge was performed until 5 Ah was reached (however, the end-of-discharge voltage was 2.0 V). A series of operations was defined as one cycle, and 1000 cycles were performed. For each of the batteries of Examples 6 and 7, constant current charging was performed at a current value of 30 A at a current value of 30 A until the voltage reached 3.85 V, and the discharge capacity reached 1.5 Ah at a current value of 30 A. A series of operations for performing constant-current discharge (however, the discharge end voltage is 2.0 V) was set as one cycle, and this was performed for 1000 cycles. And the capacity maintenance rate was calculated | required by expressing the value which remove | divided the discharge capacity of 1000th cycle by the discharge capacity of 1st cycle in percentage, and the high temperature charge / discharge cycle characteristic was evaluated.

Table 2 shows the results of the high-temperature storage tests 1 and 2 and the high-temperature charge / discharge cycle characteristics evaluation.

As shown in Examples 1 to 8, in the present invention, heat fusion such as a nonwoven fabric made of polyimide or a nonwoven fabric made of cellulose is made by crimping and joining at least a part of the peripheral portion of the separator disposed on both sides of the electrode. Since it is possible to easily join separators that cannot be joined by adhesion, productivity and reliability are the same as when joining a microporous film made of PE by thermal welding, even when using a separator with high heat resistance. It is possible to provide a non-aqueous secondary battery excellent in the above.

The present invention can be implemented in other forms as long as it does not depart from the spirit of the present invention. The embodiments disclosed in the present application are examples, and the present invention is not limited to these embodiments. The scope of the present invention is construed in preference to the description of the appended claims rather than the description of the above specification, and all modifications within the scope equivalent to the claims are construed in the scope of the claims. included.

The nonaqueous secondary battery of the present invention can ensure high reliability in addition to good productivity even when it has a particularly excellent heat resistance structure (a structure using a heat resistant separator). Therefore, it can be preferably used for applications that are highly likely to be placed in a high temperature environment such as in-vehicle use, and also applied to applications where conventionally known non-aqueous secondary batteries are used. Can do.

DESCRIPTION OF SYMBOLS 10 Positive electrode 11 Positive electrode mixture layer 12 Positive electrode collector 13 Tab part 20 Negative electrode 21 Negative electrode mixture layer 22 Negative electrode collector 23 Tab part 30 Bag-shaped separator 30a Separator 30b Separator 31 Crimp part 100 Nonaqueous secondary battery 101 Metal Laminate film exterior body 102 Laminated electrode body 103 Positive electrode external terminal 104 Negative electrode external terminal

Claims

A non-aqueous secondary battery having a laminated electrode body in which a positive electrode and a negative electrode are laminated via a separator,
The separators disposed on both sides of at least one of the positive electrode and the negative electrode each have a crimping portion at least at a part of a peripheral portion thereof, and are joined to each other at the crimping portion. Non-aqueous secondary battery.
The non-aqueous secondary battery according to claim 1, wherein the crimping portion is bent in a thickness direction of the separator.
The non-aqueous secondary battery according to claim 1 or 2, wherein the separator has a melting point of 250 ° C or higher or contains a material having no melting point.
The non-aqueous secondary battery according to claim 3, wherein the separator contains at least one resin selected from the group consisting of polyamide, polyimide, polyamideimide, polyphenylene sulfide, polyester, polyacrylonitrile, aramid, and cellulose. .
The non-aqueous secondary battery according to claim 4, wherein the separator is made of a nonwoven fabric having a porosity of 50% or more.
The non-aqueous secondary battery according to claim 3, wherein the separator has a layer mainly containing inorganic particles having a heat resistant temperature of 250 ° C or higher.
A method for producing a non-aqueous secondary battery having a laminated electrode body in which a positive electrode and a negative electrode are laminated via a separator,
Arranging a separator on both sides of at least one of the positive electrode and the negative electrode;
And a step of pressure-bonding and joining at least a part of the peripheral edges of the separators arranged on both sides of the electrode.
The method for manufacturing a non-aqueous secondary battery according to claim 7, wherein the joining by the pressure bonding is performed by corrugating.