JP2012014884A - Nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery that has superior safety and excellent load characteristics.SOLUTION: The nonaqueous secondary battery having an electrical quantity of 5 Ah or greater has two separators between a positive electrode and a negative electrode which face each other. One of the two separators is a laminate type separator which includes a porous layer (I) composed a finely porous film made principally of thermoplastic resin, and a porous layer (II) mainly containing an inorganic filler with 150°C or greater in heat-resistant temperature, with a porosity being 50 to 90%. The other one of the two separators is a separator made of resin which is not molten at 180°C or less and formed of nonwoven fabric having a basis weight of 5-10 g/m, with the porosity being 50-90%.

Description

  The present invention relates to a non-aqueous secondary battery having excellent safety and good load characteristics.

  In recent years, non-aqueous secondary batteries have been desired to have high output so that they can be used for industrial machinery or in-vehicle power supplies, and accompanying this, for example, batteries used in small portable devices. Compared to, there is a need for further safety improvements.

  In order to apply to such applications, non-aqueous secondary batteries with various improvements have been proposed. For example, Patent Document 1 proposes a non-aqueous secondary battery with improved safety by using a separator composed of a plurality of layers and a non-aqueous electrolyte to which an aromatic compound having a benzene ring is added. Yes.

  The battery described in Patent Document 1 has sufficient safety when applied to industrial machinery and in-vehicle power supplies. However, in the future, higher output is required for batteries applied to such applications. There is still room for improvement in this respect.

  Patent Document 2 uses a separator having a microporous film layer mainly composed of a thermoplastic resin and a porous layer mainly composed of a filler having a heat resistant temperature of 150 ° C. or higher, and the voltage is not less than a specific value. In such a case, a laminate type non-aqueous secondary battery has been proposed in which an additive that reacts with the positive electrode active material to generate gas is added to the positive electrode or the non-aqueous electrolyte.

  Since the battery described in Patent Document 2 can ensure the safety required for industrial machines and on-vehicle power supplies while suppressing an increase in the thickness of the separator, its load characteristics can be improved.

JP 2006-201693 A JP 2009-277397 A

  An object of the present invention is to provide a non-aqueous secondary battery that is excellent in safety and has good load characteristics by means different from the means described in Patent Document 2.

The non-aqueous secondary battery of the present invention that has achieved the above object has an electric quantity of 5 Ah or more, and has two separators between the positive electrode and the negative electrode facing each other. One of the separators has a porous layer (I) composed of a microporous film mainly composed of a thermoplastic resin and a porous layer (II) mainly composed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher. In addition, the separator is a laminated separator having a porosity of 50 to 90%, and the other of the two separators is made of a resin that does not melt at 180 ° C. or lower and has a basis weight of 5 to 10 g. / m consists of ^two nonwoven porosity is characterized in that 50 to 90% of the separator.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous secondary battery which is excellent in safety | security and has a favorable load characteristic can be provided.

In the nonaqueous secondary battery of the present invention, two separators are disposed between the positive electrode and the negative electrode facing each other. Of the two separators, one is a porous layer (I) composed of a microporous film mainly composed of a thermoplastic resin, and a porous layer (II) mainly composed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher. And a porosity of 50 to 90% or more (hereinafter abbreviated as “laminated separator”), and the other is made of a resin that does not melt at 180 ° C. or lower. And a separator having a basis weight of 5 to 10 g / m ² and a porosity of 50 to 90% (hereinafter abbreviated as “nonwoven fabric separator”).

  The porous layer (I) according to the laminated separator is mainly for ensuring a shutdown function, and a thermoplastic resin in which the non-aqueous secondary battery is a main component of the porous layer (I) When the temperature exceeds the melting point, the thermoplastic resin related to the porous layer (I) melts and closes the pores of the separator, thereby causing a shutdown that suppresses the progress of the electrochemical reaction.

  Further, the porous layer (II) according to the laminated separator has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the non-aqueous secondary battery is increased. Yes, its function is secured by an inorganic filler having a heat resistant temperature of 150 ° C. or higher. That is, when the battery becomes hot, even if the porous layer (I) shrinks, the porous layer (II) that does not easily shrink can cause the positive and negative electrodes directly when the separator is thermally contracted. It is possible to prevent a short circuit due to the contact. Moreover, since this heat-resistant porous layer (II) acts as a skeleton of the separator, the thermal contraction of the porous layer (I), that is, the thermal contraction of the entire separator itself can be suppressed.

  Thus, in addition to the original function of the separator (the function of separating the positive electrode and the negative electrode satisfactorily during normal use of the battery), the laminated separator has excellent heat shrinkage resistance at high temperatures and is non-aqueous. While the safety of the secondary battery can be improved, the relatively dense structure tends to inhibit the passage of ions. Therefore, for example, in order to improve the load characteristics of the battery, it is preferable to make the laminated separator as thin as possible.

  However, when the laminated separator is thinned, heat shrinkage is impaired, and there is a problem that the effect of suppressing thermal runaway when a metal piece as stabbed as evaluated by a nail penetration test is reduced, for example, In particular, in a battery having a large amount of electricity of 5 Ah or more, there is a possibility that sufficient safety cannot be ensured.

  Therefore, in the present invention, the nonwoven fabric separator is used together with the laminated separator. Since the nonwoven fabric separator is a nonwoven fabric, it is difficult to shrink by heat and is made of a resin having high heat resistance. For example, it is possible to compensate for a decrease in battery safety caused by thinning the laminated separator. . In addition, the nonwoven fabric separator has good ion permeability by having a specific basis weight and porosity, and suppresses deterioration in load characteristics of the battery due to the combined use with the laminated separator. it can.

  As described above, in the present invention, by using the laminated separator and the nonwoven fabric separator in combination, it has a large amount of electricity as required for industrial machinery and on-vehicle power supplies, and has excellent safety and high. It is possible to provide a non-aqueous secondary battery that can ensure load characteristics.

  The thermoplastic resin as the main component of the porous layer (I) of the laminated separator has an electrical insulation property, is electrochemically stable, and has a non-aqueous electrolysis provided in the battery described in detail later. There is no particular limitation as long as it is a thermoplastic resin that is stable to a liquid or a solvent (details will be described later) used in producing a laminated separator, but polyolefins such as PE, PP, ethylene-propylene copolymer; Polyesters such as polyethylene terephthalate and copolyesters are preferred.

  Note that the laminated separator has a property of closing the pores (that is, a shutdown function) at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower). preferable. For this reason, the porous layer (I) has a melting point, that is, a melting temperature measured using a differential scanning calorimeter (DSC) of 80 ° C. or higher (more preferably 100 ° C. or higher) according to JIS K 7121. ) More preferably, a thermoplastic resin having a temperature of 170 ° C. or lower (more preferably 150 ° C. or lower) is used as its constituent component, which is a single-layer microporous film mainly composed of PE, or 2 of PE and PP. It is preferably a laminated microporous membrane having 5 layers laminated.

  For example, when the porous layer (I) is composed of a thermoplastic resin having a melting point of 80 ° C. or more and 150 ° C. or less such as PE and a thermoplastic resin having a melting point exceeding 150 ° C. such as PP. For example, a microporous film formed by mixing PE and a resin having a higher melting point than PE such as PP is used as a porous layer (I), or has a higher melting point than PE such as a PE layer and a PP layer. When the laminated microporous film constituted by laminating the layers made of the resin is used as the porous layer (I), the melting point of the thermoplastic resin constituting the porous layer (I) is 80 The resin (for example, PE) having a temperature of from 150 ° C. to 150 ° C. is preferably 30% by mass or more, and more preferably 50% by mass or more.

  As the microporous membrane as described above, for example, a microporous membrane made of the above-described exemplary thermoplastic resin used in a non-aqueous secondary battery such as a conventionally known lithium ion secondary battery, that is, Alternatively, an ion-permeable microporous membrane prepared by a solvent extraction method, a dry method or a wet stretching method can be used.

  Further, the porous layer (I) may contain a filler or the like in order to improve the strength and the like within a range that does not impair the action of imparting the shutdown function to the separator. Examples of the filler that can be used for the porous layer (I) include the same fillers that can be used for the porous layer (II) described later (an inorganic filler having a heat resistant temperature of 150 ° C. or higher).

  The particle diameter of the filler is an average particle diameter, for example, preferably 0.01 μm or more, more preferably 0.1 μm or more, preferably 10 μm or less, more preferably 1 μm or less. The average particle diameter of the filler referred to in the present specification is measured by, for example, using a laser scattering particle size distribution meter (for example, “LA-920” manufactured by HORIBA), dispersing these fine particles in a medium in which the filler is not dissolved. The same applies to the inorganic filler according to the porous layer (II) described later. ].

  By providing the porous layer (I) having the above-described configuration, it becomes easy to provide a shutdown function to the separator, and it is possible to easily ensure safety when the internal temperature of the battery rises.

  The content of the thermoplastic resin in the porous layer (I) is preferably as follows, for example, in order to make it easier to obtain the shutdown effect. Since the thermoplastic resin is the main component of the porous layer (I), it is 50% by volume or more, more preferably 70% by volume or more, in the total volume of all the components of the porous layer (I), It may be 100% by volume.

  The inorganic filler according to the porous layer (II) has a heat-resistant temperature of 150 ° C. or higher (“heat-resistant temperature is 150 ° C. or higher” as used herein means that deformation such as softening is not observed at least at 150 ° C. However, it may be any electrochemically stable material that is stable to the non-aqueous electrolyte of the battery and that is not easily oxidized or reduced within the battery operating voltage range. In addition, alumina, silica, and boehmite are preferable. Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to the desired numerical values, making it easy to accurately control the porosity of the porous layer (II). It becomes. In addition, as for the inorganic filler whose heat-resistant temperature is 150 degreeC or more, the thing of the said illustration may be used individually by 1 type, and may use 2 or more types together, for example.

  The shape of the inorganic filler having a heat resistant temperature of 150 ° C. or higher related to the porous layer (II) is not particularly limited, and is substantially spherical (including true spherical), substantially elliptical (including elliptical), plate-like, etc. Various shapes can be used.

  Further, the average particle diameter of the inorganic filler having a heat resistant temperature of 150 ° C. or higher related to the porous layer (II) is preferably 0.3 μm or more because the ion permeability is lowered if it is too small. More preferably, it is 5 μm or more. In addition, if the inorganic filler having a heat resistant temperature of 150 ° C. or higher is too large, the electrical characteristics are likely to be deteriorated. Therefore, the average particle diameter is preferably 5 μm or less, and more preferably 2 μm or less.

  Since the inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (II) is mainly contained in the porous layer (II), the amount in the porous layer (II) Is 50% by volume or more, preferably 70% by volume or more, more preferably 80% by volume or more, and still more preferably 90% by volume or more. By making the inorganic filler in the porous layer (II) high as described above, even when the non-aqueous secondary battery becomes high temperature, the effect of suppressing the thermal contraction of the entire laminated separator is achieved. Better.

  In addition, the porous layer (II) binds inorganic fillers having a heat-resistant temperature of 150 ° C. or higher, or binds the porous layer (I) and the porous layer (II) as necessary. In view of this, it is preferable to contain an organic binder. From such a viewpoint, the preferred upper limit of the amount of the inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (II) is, for example, that of the porous layer (II) It is 99.5 volume% in the whole volume of a structural component. If the amount of the inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (II) is less than 70% by volume, for example, it is necessary to increase the amount of the organic binder in the porous layer (II). In some cases, the pores of the porous layer (II) are easily filled with an organic binder, and the function as a separator may be lowered. In addition, when the porous layer is made porous by using a pore-opening agent, the filler There is a concern that the effect of suppressing heat shrinkage may be reduced due to an excessive increase in the distance between each other.

  The porous layer (II) preferably contains an organic binder in order to ensure the shape stability of the separator and to integrate the porous layer (II) and the porous layer (I). Examples of organic binders include ethylene-vinyl acetate copolymers (EVA, those having a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymers, and fluorine 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 and the like. However, in particular, a heat-resistant binder having a heat-resistant temperature of 150 ° C. or higher is preferably used. As the organic binder, those exemplified above may be used singly or in combination of two or more.

  Among the organic binders exemplified above, highly flexible binders such as EVA, ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are preferable. Specific examples of such highly flexible organic binders include Mitsui DuPont Polychemical's “Evaflex Series (EVA)”, Nihon Unicar's EVA, Mitsui DuPont Polychemical's “Evaflex-EAA Series (Ethylene). -Acrylic acid copolymer) ", Nippon Unicar EEA, Daikin Industries" DAI-EL Latex Series (Fluororubber) ", JSR" TRD-2001 (SBR) ", Nippon Zeon" BM-400B " (SBR) ".

  When the organic binder is used for the porous layer (II), it can be used in the form of an emulsion dissolved or dispersed in the solvent for the composition for forming the porous layer (II) described later. Good.

  For example, the laminated separator includes a porous layer (II) -forming composition (such as a liquid composition such as a slurry) containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher, and a porous layer (I). It can be manufactured by coating the surface of a microporous membrane for construction and drying to a predetermined temperature to form a porous layer (II).

  The composition for forming the porous layer (II) contains an inorganic binder having a heat-resistant temperature of 150 ° C. or higher and, if necessary, an organic binder and the like, and these are dispersed in a solvent (including a dispersion medium, the same applies hereinafter). It has been made. The organic binder can be dissolved in a solvent. The solvent used in the composition for forming the porous layer (II) is not particularly limited as long as it can uniformly disperse the inorganic filler and can uniformly dissolve or disperse the organic binder. Common organic solvents such as hydrocarbons, furans such as tetrahydrofuran, and ketones such as methyl ethyl ketone and methyl isobutyl ketone are preferably used. In addition, for the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the organic binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) are appropriately added. It is also possible to control the interfacial tension.

  The composition for forming the porous layer (II) preferably has a solid content containing, for example, an inorganic filler having a heat resistant temperature of 150 ° C. or higher and an organic binder, for example, 10 to 80% by mass.

  In addition, the porous layer (II) forming composition is applied onto a substrate such as a film or a metal foil, dried at a predetermined temperature, and then peeled off from the substrate as necessary to form the porous layer (II). A laminated separator can also be produced by forming a porous film and laminating and integrating the porous film and the microporous film for forming the porous layer (I). In this case, in order to integrate the microporous membrane for forming the porous layer (I) and the porous membrane to be the porous layer (II), for example, the porous layer (I) and the porous layer ( It is possible to use a method of superimposing II) and pasting them together using a roll press or the like.

  In the laminated separator, the porous layer (I) and the porous layer (II) do not have to be one each, and a plurality of layers may be present in the separator. For example, a configuration in which the porous layer (I) is disposed on both sides of the porous layer (II) or a configuration in which the porous layer (II) is disposed on both sides of the porous layer (I) may be employed. However, increasing the number of layers may increase the thickness of the separator and increase the internal resistance of the battery or decrease the energy density. Therefore, it is not preferable to increase the number of layers. The total number of the porous layers (I) and (II) is preferably 5 or less.

The porosity of the multilayer separator is 50% or more and 60% or more in a dried state in order to secure a liquid retention amount of the non-aqueous electrolyte and improve ion permeability. preferable. On the other hand, from the viewpoint of securing strength, the porosity of the laminated separator is 90% or less, preferably 80% or less, in a dry state. In addition, the porosity: P (%) of the said laminated separator and the nonwoven fabric separator mentioned later is each component i from the thickness of a separator, the mass per area, and the density of a structural component using the following (1) Formula. Can be calculated by calculating the sum of
P = {1- (m / t) / (Σa _i · ρ _i )} × 100 (1)
Here, in the above formula, a _i : ratio of component i when the total mass is 1, ρ _i : density of component i (g / cm ³ ), m: mass per unit area of the separator (g / cm ² ), t: thickness of separator (cm).

In the case of the multilayer separator, in the formula (1), m is the mass per unit area (g / cm ² ) of the porous layer (I), and t is the thickness of the porous layer (I) ( cm), the porosity: P (%) of the porous layer (I) can also be obtained using the formula (1). The porosity of the porous layer (I) determined by this method is preferably 30 to 80%.

Further, in the case of the multilayer separator, in the formula (1), m is the mass per unit area (g / cm ² ) of the porous layer (II), and t is the thickness of the porous layer (II) ( cm), the porosity: P (%) of the porous layer (II) can also be obtained using the formula (1). The porosity of the porous layer (II) obtained by this method is preferably 50 to 90%.

  The total thickness of the laminated separator is preferably 30 μm or less, more preferably 20 μm or less, from the viewpoint of further improving the load characteristics of the battery. However, if the laminated separator is too thin, there is a possibility that the effect of improving the safety of the battery due to the use of this separator may be reduced. Therefore, the total thickness is preferably 10 μm or more, and is 12 μm or more. More preferably.

  In the laminated separator, the thickness of the porous layer (II) [when the separator has a plurality of porous layers (II), the total thickness] is determined by each of the functions of the porous layer (II). Is more preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of more effectively exhibiting. However, if the porous layer (II) is too thick, the total thickness of the laminated separator becomes large. Therefore, the thickness of the porous layer (II) is preferably 20 μm or less, and preferably 16 μm or less. It is more preferable.

  Further, in the laminated separator, the thickness of the porous layer (I) [when the separator has a plurality of porous layers (I), the total thickness thereof. same as below. ] Is preferably 2 μm or more, and more preferably 3 μm or more, from the viewpoint of more effectively exerting the above-described action (particularly shutdown action) due to the use of the porous layer (I). However, if the porous layer (I) is too thick, in addition to the total thickness of the laminated separator becoming larger, the force that the porous layer (I) tends to heat shrink becomes larger, and the laminated type There exists a possibility that the effect | action which suppresses the thermal contraction of the whole separator may become small. Therefore, the thickness of the porous layer (I) is preferably 10 μm, and more preferably 5 μm or less.

  The nonwoven fabric used for the nonwoven fabric separator according to the battery of the present invention is a resin that does not melt at 180 ° C. or lower, that is, the melting temperature measured using DSC exceeds 180 ° C. in accordance with the provisions of JIS K 7121. For example, it is made of a resin that does not exhibit melting behavior at a temperature of 180 ° C. or lower when the melting temperature is measured.

  Specific examples of such a resin include, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), aramid, polyimide, and the like. In addition, the nonwoven fabric may be comprised only with 1 type of the said exemplary resin, and may be comprised with 2 or more types. Moreover, the nonwoven fabric may be comprised only with the resin of the said illustration, and the fiber which consists of the said resin of the said illustration may adhere | attach with a well-known adhesive etc. as needed.

The nonwoven fabric constituting the nonwoven fabric separator has a basis weight of 5 g / m ² or more, preferably 6 g / m ² or more. By using a separator composed of such a nonwoven fabric together with the laminated separator, For example, the short-circuit resistance when a metal piece such as a nail is pierced into the battery can be increased, and the safety of the battery can be improved. However, if the basis weight of the nonwoven fabric constituting the nonwoven fabric separator is too large, the holding capacity of the non-aqueous electrolyte is lowered and the ion permeation is hindered, so the basis weight is 10 g / m ² or less. , 9 g / m ² or less is preferable.

  In addition, the non-woven fabric separator has a porosity determined by the above formula (1) of 50% or more in a dry state in order to ensure a liquid retention amount of the non-aqueous electrolyte and improve ion permeability. It is preferable that it is 60% or more. On the other hand, from the standpoint of securing strength, the porosity obtained by the formula (1) of the multilayer separator is 90% or less and preferably 85% or less in a dried state.

  If the nonwoven fabric separator is too thin, the battery safety improvement effect may be reduced. Therefore, the thickness is preferably 10 μm or more, and more preferably 15 μm or more. However, if the nonwoven fabric separator is too thick, the distance between the electrodes is increased, so that the effect of improving the load characteristics is reduced or the charge / discharge cycle characteristics are reduced. Therefore, the thickness is 50 μm or less. It is preferable that it is 40 μm or less.

  The non-aqueous secondary battery of the present invention has an electric quantity of 5 Ah or more, and may have the laminated separator and the nonwoven fabric separator between the positive electrode and the negative electrode facing each other. The structure and structure are not particularly limited, and various structures and structures employed in conventionally known nonaqueous secondary batteries can be applied.

  The positive electrode has, for example, a positive electrode mixture layer containing a positive electrode active material, an electron conduction aid, a binder, etc., and the positive electrode mixture layer is formed on one or both sides of the current collector. Can be mentioned.

  As the positive electrode active material, any positive electrode active material used in conventionally known non-aqueous secondary batteries can be used without particular limitation. Specific examples include lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt manganese composite oxide, lithium titanate, vanadium oxide, and molybdenum oxide. One species may be used alone, or two or more species may be used in combination.

  Among the positive electrode active materials exemplified above, it is more preferable to use a lithium manganese composite oxide. Lithium-manganese composite oxides are particularly safe among lithium-containing composite oxides in the charged state. Therefore, while introducing a large amount into the battery and increasing the capacity so that the amount of electricity is 5 Ah or more, A battery with high performance can be obtained.

  Examples of the lithium manganese complex oxide include lithium manganese complex oxides containing additive elements such as Al, Mg, B, and Ba in addition to lithium manganate. In the case of the lithium manganese composite oxide containing the above additive element, the manganese content may be 90 mol% or more when the total of the manganese content and the additive element content is 100 mol%. Preferably, this makes it possible to satisfactorily ensure the effect of the additive element (for example, the effect of improving the stability of the lithium manganese composite oxide at a high temperature) while suppressing a decrease in capacity due to the use of the additive element.

  Graphite, carbon black, acetylene black and the like can be used as the electron conduction aid for the positive electrode, but it is more preferable to use carbon black as the main component.

  As the binder for the positive electrode, polytetrafluoroethylene (PTFE) dispersion, powdered PTFE, rubber binder, polyvinylidene fluoride (PVDF), or the like can be used, but PVDF is more preferable.

  As the positive electrode current collector, a foil made of aluminum, titanium or the like, a plain weave metal net, an expanded metal, a lath net, a punching metal, or the like can be used, but an aluminum foil is more preferable. The thickness of the current collector is preferably 10 to 20 μm.

  For the positive electrode, for example, a positive electrode mixture-containing paste is prepared by dispersing the positive electrode mixture composed of the positive electrode active material, the electron conduction auxiliary agent, and the binder in a solvent such as N-methyl-2-pyrrolidone (NMP). (The binder may be dissolved in a solvent), which is applied to one or both sides of the current collector, dried, and subjected to press treatment as necessary to form a positive electrode mixture layer. it can. In addition, the manufacturing method of the positive electrode which concerns on this invention is not necessarily limited to the said manufacturing method, You may manufacture by another manufacturing method.

  In the positive electrode mixture layer according to the positive electrode, the content of the positive electrode active material is 95 to 99% by mass, the content of the electron conduction assistant is 0.5 to 2% by mass, and the content of the binder is 0.5 to 3% by mass. % Is preferred. Moreover, it is preferable that the thickness of a positive mix layer is 40-100 micrometers per single side | surface of a positive electrode electrical power collector.

  Examples of the negative electrode according to the nonaqueous secondary battery of the present invention include those in which a negative electrode mixture layer containing a negative electrode active material, a binder and the like is formed on one side or both sides of a current collector.

  The active material used for the negative electrode is preferably a carbon material such as natural graphite, mesophase carbon, or amorphous carbon. These carbon materials may be used alone or in combination of two or more.

  Examples of the binder for the negative electrode include cellulose such as CMC and hydroxypropyl cellulose (HPC); rubber-based binders such as SBR and acrylic rubber; these may be used alone or in combination of two or more. May be.

  As the current collector of the negative electrode, a foil made of copper, nickel, stainless steel, etc., a plain weave wire mesh, an expanded metal, a punching metal, or the like can be used, but it is more preferable to use a copper foil. The thickness of the current collector is preferably 5 to 15 μm.

  For the negative electrode, for example, a negative electrode mixture-containing paste is prepared by dispersing a positive electrode mixture composed of the negative electrode active material and a binder in a solvent such as NMP or water (the binder may be dissolved in the solvent). ), Which is applied to one or both sides of the current collector and dried to form a negative electrode mixture layer. In addition, the manufacturing method of the negative electrode which concerns on this invention is not necessarily limited to the said manufacturing method, You may manufacture by another manufacturing method.

  In the negative electrode mixture layer relating to the negative electrode, the content of the negative electrode active material is preferably 90 to 99.9% by mass, and the content of the binder is preferably 0.1 to 10% by mass. Moreover, it is preferable that the thickness of a negative mix layer is 40-100 micrometers per single side | surface of a negative electrode collector.

  In the battery of the present invention, a laminated electrode body in which the positive electrode and the negative electrode are overlapped with both of the laminated separator and the nonwoven fabric separator interposed therebetween, and a winding obtained by winding the laminated electrode body in a spiral shape It can be used in the form of an electrode body.

  In the electrode body, the arrangement of the laminated separator and the nonwoven fabric separator is not particularly limited, and may be arranged such that the laminated separator faces the positive electrode and the nonwoven fabric separator faces the negative electrode, and the laminated separator faces the negative electrode. The laminated separator may be disposed so as to face the positive electrode. However, in the case where the constituent resin of the porous layer (I) according to the multilayer separator is, for example, PE, the porous layer according to the multilayer separator (in order to prevent oxidation of the porous layer (I) by the positive electrode ( It is preferable to arrange both separators so that I) does not face the positive electrode.

As the non-aqueous electrolyte according to the battery of the present invention, a non-aqueous electrolyte used in a conventionally known non-aqueous secondary battery, for example, a solution in which a lithium salt is dissolved in an organic solvent is used. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , and LiN (CF ₃ SO ₂ ) ₂ . Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dimethoxyethane, dioxolane, and the like. The lithium salt concentration in the nonaqueous electrolytic solution is preferably 0.2 to 1.5 mol / l, for example.

  As the battery container (exterior body), those used in conventionally known non-aqueous secondary batteries can be used. Specifically, an aluminum or stainless steel container (for example, a bottomed cylinder), the battery lid being laser-welded to the battery container or sealed by a crimp seal through packing. Can be used. The positive electrode and the negative electrode (electrode body) are isolated from the container by an insulator made of glass or resin in the battery container.

  In addition, it is good also as a structure which can provide the safety | security when the battery internal pressure rises rapidly by providing the vent which consists of a thin part in the bottom of a battery cover or a battery container.

  In addition, a laminate film having a metal foil (such as an aluminum foil) as a core material can be used for the battery container.

  The non-aqueous secondary battery of the present invention has a large amount of electricity such as 5 Ah or more, and excellent load characteristics and safety. Taking advantage of such characteristics, the non-aqueous secondary battery can be used for industrial machinery, in-vehicle power supplies, and the like. It can be used for various applications to which conventionally known non-aqueous secondary batteries are applied, including applications for batteries.

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

Example 1
<Production of laminated separator>
1000 g of water, 1000 g of a polyhedral boehmite synthetic product (aspect ratio 1.4, D50 = 0.63 μm) as an inorganic filler, and an acrylate copolymer as a binder (commercially composed mainly of butyl acrylate as a monomer component) Acrylate copolymer; 3 parts by mass with respect to 100 parts by mass of the inorganic filler) was stirred and dispersed for 1 hour using a three-one motor to prepare a uniform slurry [slurry for forming a porous layer (II)] did.

For the porous layer (I), a PE microporous film having a thickness of 16 μm and a porosity of 41% and subjected to corona discharge treatment on one side was prepared. On the surface of the PE microporous film on the side subjected to the corona discharge treatment, the slurry is uniformly applied using a die coater so that the total thickness after drying is 20 μm, and dried to form a laminated type. A separator was produced. This laminated separator has a porosity of 80%, and the porous layer (II) has a boehmite volume ratio calculated by setting the specific gravity of boehmite to 3 g / cm ³ and the specific gravity of the binder to 1 g / cm ^3. It was 92 volume%.

<Preparation of positive electrode>
A positive electrode mixture-containing paste was prepared by sufficiently mixing lithium manganate as a positive electrode active material: 94% by mass, carbon: 3% by mass, and PVDF: 3% by mass using an appropriate amount of NMP as a solvent. This positive electrode mixture-containing paste is applied to both sides of an aluminum foil having a thickness of 15 μm, dried at 110 ± 10 ° C., and subjected to press treatment to a thickness of 150 μm, and then a positive electrode mixture layer per one side of the aluminum foil The positive electrode was obtained by cutting so as to have a size of 197 × 109 mm.

<Production of negative electrode>
Carbon: 97.8% by mass, CMC: 1.2% by mass, and SBR: 1% by mass were sufficiently mixed with an appropriate amount of pure water as a solvent to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste is applied to both sides of a copper foil having a thickness of 10 μm, dried at 110 ± 10 ° C., subjected to press treatment to a thickness of 100 μm, and then the negative electrode mixture layer per one side of the copper foil The negative electrode was obtained by cutting so as to have a size of 205 × 117 mm.

<Battery assembly>
15 sheets of the positive electrode and 16 sheets of the negative electrode are used so that the amount of electricity of the assembled battery is 10 Ah, and the stacked separator and the nonwoven fabric are used between the positive electrode and the negative electrode facing each other. While interposing separators (both separators are 210 × 117 mm in size), a laminated electrode body was obtained by alternately stacking both outer layers to be negative electrodes. The nonwoven fabric separator was a PET nonwoven fabric having a basis weight of 8.3 g / m ² , a porosity of 80%, and a thickness of 31.2 μm. In the laminated electrode body, the laminated separator and the nonwoven fabric separator were arranged so that the porous layer (II) of the laminated separator was opposed to the positive electrode.

The laminated electrode body is housed in an outer package made of an aluminum laminate film, and the positive electrode and the negative electrode are connected to an external terminal according to a conventional method, and a non-aqueous electrolyte (ethylene carbonate and chain carbonate are mixed at a volume ratio of 3: 7). After injecting 70 g of a solution (LiPF ₆ dissolved at a concentration of 1 mol / l in the solvent) into the outer package, sealing was performed to obtain a laminated nonaqueous secondary battery.

Example 2
A laminated nonaqueous secondary battery was prepared in the same manner as in Example 1 except that the nonwoven fabric separator was changed to a PET nonwoven fabric having a basis weight of 5.0 g / m ² , a porosity of 83%, and a thickness of 22 μm. Produced.

Comparative Example 1
A laminated non-aqueous secondary as in Example 1 except that the nonwoven fabric separator was changed to a nonwoven fabric made of PET having a basis weight of 3.2 g / m ² , a porosity of 85%, and a thickness of 15.8 μm. A battery was produced.

Comparative Example 2
A slurry for forming a porous layer (II) was prepared in the same manner as in Example 1 except that the amount of the acrylate copolymer as a binder was 30 parts by mass with respect to 100 parts by mass of the inorganic filler. A laminated separator was produced in the same manner as in Example 1 except that was used. This laminated separator had a porosity of 40%. A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that the laminated separator was changed to that described above.

Comparative Example 3
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that a PE microporous film having a thickness of 20 μm and a porosity of 80% was used instead of the laminated separator.

Comparative Example 4
A laminated nonaqueous secondary battery was prepared in the same manner as in Comparative Example 3 except that the nonwoven fabric separator was changed to a nonwoven fabric made of PP and having a basis weight of 8.0 g / m ² , a porosity of 80%, and a thickness of 30 μm. Produced.

  Table 1 shows the configurations of the separators used in the batteries of Examples 1-2 and Comparative Examples 1-4.

  In the column of “Laminated separator” in Table 1, “Porous layer (I)” indicates the material of the microporous film (thermoplastic resin) used for the porous layer (I) and “Porous layer (I)”. "II)" indicates the type of inorganic filler having a heat resistant temperature of 150 ° C or higher used for the porous layer (II).

  Prior to battery evaluation, short-circuit resistance was measured by the following nail penetration test using the positive electrode, negative electrode, laminated separator and nonwoven fabric separator used in the batteries of Examples 1-2 and Comparative Examples 1-4.

  The positive electrode is cut so that the size of the positive electrode mixture layer per one side of the aluminum foil is 50 × 30 mm, and the negative electrode is cut so that the size of the negative electrode mixture layer per one side of the copper foil is 53 × 33 mm Disconnected. Furthermore, the laminated separator and the nonwoven fabric separator used for each battery were each cut into a size of 70 × 40 mm.

  And the sample which pinched | interposed each lamination type separator and the nonwoven fabric separator between the positive electrode and the negative electrode was produced in the same way as producing the laminated electrode body of each battery. And the needle | hook of diameter 3mm was penetrated to each sample, without containing a non-aqueous electrolyte, and resistance (short circuit resistance) between a positive electrode and a negative electrode was measured.

  Moreover, about the nonaqueous secondary battery of Examples 1-2 and Comparative Examples 1-4, the following load characteristic evaluation and a 130 degreeC exposure test were done.

<Evaluation of load characteristics>
For each battery, constant current charging was performed until the voltage reached 4.2 V at a current value of 2 A, and then constant voltage charging was performed at 4.2 V. The total charging time was 8 hours. Thereafter, discharging was performed at a current value of 10 A (corresponding to 1 C) until it reached 3 V, and a discharge capacity (10 A discharge capacity) was measured.

  Further, each battery was charged at a constant current-constant voltage under the same conditions as described above, and then discharged until it reached 3 V at a current value of 50 A (equivalent to 5 C) to measure the discharge capacity (50 A discharge capacity). And about each battery, the value which remove | divided 50A discharge capacity by 10A discharge capacity was represented by the percentage, and the capacity | capacitance maintenance factor was calculated | required. The higher the capacity retention rate, the better the load characteristics of the battery.

<130 ° C exposure test>
For each battery, constant-current-constant-voltage charging was performed under the same conditions as when the load characteristics were evaluated, then the temperature was increased to 130 ° C. in a thermostatic bath, and further maintained at 130 ° C. for 2 minutes. Was measured. Moreover, each battery was taken out from the thermostat after the said holding | maintenance, and the open circuit voltage was measured.

  Table 2 shows the results of the nail penetration test, load characteristic evaluation, and 130 ° C. exposure test.

  As is clear from Table 2, the batteries of Examples 1 and 2 have a high capacity retention rate at the time of load characteristic evaluation and have good load characteristics. In addition, the batteries of Examples 1 and 2 have suppressed surface temperature rise during the 130 ° C. exposure test, and the open circuit voltage after the exposure test is maintained high, and the safety at high temperatures is good. is there. Furthermore, since the separators used in the batteries of Examples 1 and 2 have high short-circuit resistance during the nail penetration test, the batteries of Examples 1 and 2 using these separators were stuck with a metal piece such as a nail. At this time, the resistance value increases and the current is cut off. Therefore, it can be said that the batteries of Examples 1 and 2 are excellent in safety when a metal piece is stabbed.

  On the other hand, the battery of Comparative Example 1 using a nonwoven fabric separator having a small basis weight has a low short-circuit resistance during the nail penetration test of the separator and is inferior in safety when a metal piece is stuck. In addition, the battery of Comparative Example 2 using the laminated separator having a low porosity has poor load characteristics. In addition, the battery of Comparative Example 3 using a PE microporous membrane separator instead of the laminated separator, and the PE microporous membrane separator instead of the laminated separator and 180 ° C. or less for the nonwoven fabric separator The battery of Comparative Example 4 that uses PP that melts at a temperature of 10 ° C. has a high surface temperature in the 130 ° C. exposure test, a low open circuit voltage after the 130 ° C. exposure test, and safety at high temperatures. Inferior.

Claims (2)

A non-aqueous secondary battery having an electric quantity of 5 Ah or more,
It has two separators between the positive and negative electrodes facing each other,
Of the two separators, one is a porous layer (I) composed of a microporous film mainly composed of a thermoplastic resin, and a porous layer (II) mainly composed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher. And a porosity separator having a porosity of 50 to 90%,
Of the two separators, the other is made of a non-melting resin at 180 ° C. or lower, is made of a nonwoven fabric having a basis weight of 5 to 10 g / m ² , and has a porosity of 50 to 90%. There is a non-aqueous secondary battery.   The nonaqueous secondary battery according to claim 1, wherein the positive electrode mixture layer including the lithium manganese composite oxide, the electron conduction assistant, and the binder has a positive electrode formed on one side or both sides of the current collector.