Separator for electrochemical element, electrochemical element, and method for manufacturing same

Abstract

Provided are: a separator for an electrochemical element, the separator being able to be bonded to an electrode without heating; an electrochemical element comprising the separator; and a method for manufacturing the electrochemical element.　This separator for an electrochemical element is characterized in that: the separator comprises a substrate layer that comprises a porous film and a bonding layer for bonding to an electrode of an electrochemical element; the bonding layer contains a particulate resin (A); the melting point of the resin (A) is in the range 75–140°C; and the basis weight of the resin (A) in the bonding layer is at least 0.05 g / m2. This electrochemical element is characterized in that: the electrochemical element comprises this separator for an electrochemical element; and at least one electrode, of a positive electrode and a negative electrode, is bonded to the separator by the bonding layer of the separator.

Description

Separator for electrochemical element, electrochemical element and manufacturing method thereof

[0001] The present invention relates to a separator for an electrochemical element that can be bonded to an electrode without heating, an electrochemical element having the separator, and a method for producing the same.

[0002] Electrochemical elements such as secondary batteries have undergone various improvements, such as increasing capacity in response to the increasing sophistication of the devices to which they are applied. However, in order to improve the safety and stability of the characteristics of electrochemical elements, improvements are also frequently made to the separators interposed between the positive and negative electrodes.

[0003] For example, Patent Document 1 proposes a separator in which a substrate having a thickness of 25 μm or less, primarily made of a thermoplastic resin (A) with a melting point of 150 to 170°C, is provided on the surface with a thermoplastic resin (B) having a melting point 40 to 60°C lower than that of the thermoplastic resin (A). With this separator, for example, when the temperature inside an electrochemical device rises excessively, the thermoplastic resin (B) with the lower melting point melts and blocks the pores in the substrate, resulting in a shutdown. Therefore, the shape of the substrate, primarily made of a thermoplastic resin (A) with a higher melting point, is maintained until the current value inside the electrochemical device is reliably reduced. Therefore, the separator described in Patent Document 1 can effectively suppress the occurrence of internal short circuits, thereby enabling the construction of an electrochemical device with excellent safety.

[0004] In the separator described in Patent Document 1, from the viewpoint of favorably exhibiting the shutdown by the thermoplastic resin (B), the preferred basis weight of the thermoplastic resin (B) is 1 g / cm ２ That is all.

[0005] Furthermore, in order for an electrochemical element to exhibit stable characteristics during use, it is desirable to maintain a certain distance between the positive and negative electrodes, for example. However, the volume of the electrodes of an electrochemical element changes with discharge and charge, which creates a problem in that the distance between the positive and negative electrodes tends to vary as the element is used.

[0006] As a means of avoiding such problems, for example, Patent Document 2 proposes placing an adhesive resin that becomes adhesive when heated on the surface of the separator, and integrating the separator and electrodes with this adhesive resin.

[0007] Japanese Patent Application Laid-Open No. 2014-179165 (claims, paragraphs

[0014] ,

[0015] ,

[0035] , etc.) Japanese Patent Application Laid-Open No. 2011-23186

[0008] Incidentally, when a separator and an electrode are bonded with an adhesive resin, as described in Patent Document 2, the adhesive resin is typically heated to melt or soften the adhesive resin. However, when bonding by heating, if heat is not sufficiently transferred throughout the adhesive resin, the bonding strength between the separator and the electrode cannot be ensured, and the bonding process requires a certain amount of time. However, when mass-producing electrochemical elements, for example, it is desirable to perform the bonding process between the separator and the electrode continuously to minimize the time required for bonding at each location. Therefore, there is a need for the development of a technology that can bond separators and electrodes well without heating.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a separator for an electrochemical element that can be bonded to an electrode without heating, an electrochemical element having the separator, and a method for producing the same.

[0010] The separator for an electrochemical element of the present invention has a substrate layer made of a porous film and a binder layer for bonding electrodes of an electrochemical element, the binder layer containing a particulate resin (A), the melting point of the resin (A) being 75 to 140°C, and the basis weight of the resin (A) in the binder layer being 0.05 g / m ２ The present invention is characterized by the above.

[0011] The electrochemical element of the present invention comprises a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the separator is the separator for electrochemical elements of the present invention, and at least one of the positive electrode and the negative electrode and the separator is bound by the binding layer of the separator.

[0012] Furthermore, the method for producing an electrochemical element of the present invention is a method for producing an electrochemical element having a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and is characterized by comprising a step of using the separator for electrochemical elements of the present invention as the separator, overlapping at least one of the positive electrode and the negative electrode with the separator, and applying pressure at a temperature at which the resin (A) does not melt, thereby bonding the electrode and the separator.

[0013] According to the present invention, it is possible to provide a separator for an electrochemical element that can be bonded to an electrode without heating, as well as an electrochemical element having the separator and a method for producing the same.

[0014] 1 is a cross-sectional view schematically showing an example of a separator for an electrochemical element of the present invention, which is bonded to and integrated with a positive electrode and a negative electrode of an electrochemical element. 2 is a plan view schematically showing an example of an electrochemical element (non-aqueous electrolyte secondary battery) of the present invention. 3 is a cross-sectional view taken along line II in FIG.

[0015] <Separator for Electrochemical Device> The separator for an electrochemical device of the present invention (hereinafter, sometimes simply referred to as "separator") has a substrate layer made of a porous film and a binder layer for bonding electrodes of an electrochemical device. The binder layer contains a particulate resin (A), the melting point of the resin (A) is 75 to 140°C, and the basis weight of the resin (A) in the binder layer is 0.05 g / m ２ That's all.

[0016] The separator of the present invention can be well bonded to the electrode of an electrochemical device by applying pressure, for example at room temperature, without heating (without melting), while the binder layer is placed on the electrode of the electrochemical device on the binder layer side, due to the action of the binder layer containing the resin (A). Although the reason for this is unclear, it is presumed that when the binder layer contains particulate resin (A) having the melting point described above and at the basis weight described above, the particulate resin (A) is well pressed into the recesses on the surface of the electrode during pressure application, thereby enhancing the binding strength with the electrode due to an anchor effect or the like.

[0017] FIG. 1 is a cross-sectional view schematically illustrating an example of a separator of the present invention. FIG. 1 shows the separator bonded to electrodes (positive and negative electrodes) of an electrochemical element on both sides. Separator 10 has heat-resistant layers 12, 12 on both sides of substrate layer 11, and further has bonding layers 13, 13 on each of the heat-resistant layers 12, 12. The bonding layer 13 on the lower side in the figure is bonded to the positive electrode 20, and the bonding layer 13 on the upper side in the figure is bonded to the negative electrode 30, thereby integrating separator 10 with the positive electrode 20 and the negative electrode 30.

[0018] In FIG. 1, the binder layers 13, 13 are shown as uniform layers to make the layer structure of the separator easier to understand, but as described above, the resin (A) contained in the binder layers 13, 13 is in particulate form.

[0019] The resin (A) contained in the binder layer of the separator has a melting point of 75° C. or higher and 140° C. or lower. The melting point of a thermoplastic resin such as resin (A) referred to in this specification means the melting temperature measured using a differential scanning calorimeter (DSC) in accordance with the provisions of Japanese Industrial Standards (JIS) K 7121.

[0020] Among the resins having the above melting points, polymers having structural units derived from ethylene or propylene (hereinafter referred to as "PE / PP polymers") are preferably used as resin (A) because they have appropriate deformability that makes it easy to obtain the binding effect described above. Here, "structural units derived from ethylene or propylene" refers to structural units introduced by ethylene or propylene in a polymer obtained by polymerization of a monomer containing ethylene or propylene.

[0021] Examples of PE / PP polymers include ethylene polymers (polyethylene), propylene polymers (polypropylene), copolymers of ethylene and propylene, and copolymers of ethylene or propylene with an α-olefin having 5 to 20 carbon atoms. Examples of α-olefins having 5 to 20 carbon atoms used in copolymerization with ethylene or propylene include 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-nonadecene, and 1-eicosene, and one or more of these may be used.

[0022] The copolymer composition of a copolymer of ethylene or propylene and an α-olefin having 5 to 20 carbon atoms is not particularly limited as long as the melting point can be adjusted to the above value, but for example, the proportion of structural units derived from ethylene and propylene (when both ethylene-derived structural units and propylene-derived structural units are contained, the total of these) can be 75 to 95 mol % and the proportion of structural units derived from an α-olefin having 5 to 20 carbon atoms can be 5 to 25 mol % in 100 mol of structural units derived from all monomers. Here, "structural units derived from an α-olefin having 5 to 20 carbon atoms" means structural units introduced by an α-olefin having 5 to 20 carbon atoms in a copolymer obtained by polymerization of a monomer containing ethylene or propylene and an α-olefin having 5 to 20 carbon atoms.

[0023] As will be described later, the binder layer in the separator can be formed by applying a binder layer-forming composition containing the resin (A) dispersed in a medium such as water or an organic solvent onto a substrate layer made of a porous film or onto a heat-resistant layer formed on the surface of the substrate layer. To enhance the affinity with water, particularly in order to make the resin (A) an aqueous dispersion, the PE / PP polymer may have a structural unit derived from a polymerizable monomer having a polar group introduced into its main chain or side chain. Here, the term "structural unit derived from a polymerizable monomer having a polar group" refers to a structural unit introduced into the main chain or side chain of a copolymer obtained by graft polymerization of a polymerizable monomer having a polar group or by polymerization of a monomer containing ethylene or propylene and a polymerizable monomer having a polar group.

[0024] Examples of polymerizable monomers having a polar group that can be used in copolymers together with ethylene or propylene and, if necessary, an α-olefin having 5 to 20 carbon atoms include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid; derivatives of unsaturated carboxylic acids such as maleic anhydride, itaconic anhydride, and citraconic anhydride; and esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, and itaconic acid diethyl ester.

[0025] Resin (A) may be, for example, composed of only one type of PE / PP polymer, or may be a mixture of two or more different polymers, such as a mixture of two or more copolymers containing different types of α-olefins as monomers. Resin (A) may also be a mixture of an ethylene or propylene copolymer and an ethylene or propylene homopolymer.

[0026] In the binder layer, the resin (A) is in particulate form. As described above, the particulate resin (A) is pressed into the recessed portions on the surface of the electrode, thereby increasing the adhesive strength between the binder layer and the electrode, i.e., the adhesive strength between the separator and the electrode.

[0027] The average particle size of the resin (A) in the binder layer is preferably 3 μm or less, more preferably 2 μm or less, from the viewpoint of further enhancing the binding strength with the electrode. However, if the particle size of the resin (A) in the binder layer is too small, the separator may be clogged, which may reduce the electrolyte permeability and retention ability of the electrochemical device. Therefore, from the viewpoint of further enhancing the electrolyte permeability and retention ability in the separator and improving the characteristics of the electrochemical device, the average particle size of the resin (A) is preferably 0.2 μm or more, more preferably 0.3 μm or more.

[0028] The average particle size of the resin (A) referred to in this specification is the number average particle size measured using a laser scattering particle size distribution analyzer (HORIBA "LA-920") after dispersing the particles in a medium that does not swell (for example, water).

[0029] Resin (A) can be obtained, for example, by polymerizing the above-mentioned monomers using a method similar to that used for ordinary polyolefins. Some resins (A) are commercially available in a state dispersed in a medium such as water (e.g., "Chemipearl (registered trademark)" manufactured by Mitsui Chemicals, Inc.), and these can also be used. Furthermore, the average particle size of resin (A) in the binder layer can be adjusted, for example, by adjusting the dispersed particle size of resin (A) in an aqueous dispersion or organic solvent dispersion.

[0030] The basis weight of the resin (A) in the binder layer is 0.05 g / m from the viewpoint of increasing the binding strength between the separator and the electrode. ２ or more, and ２ It is preferable that the content is 0.3 g / m or more. ２ From the viewpoint of increasing the air permeability of the separator and improving the electrolyte permeability and retention of the electrochemical element, the basis weight of the resin (A) in the binder layer is preferably 0.9 g / m or more. ２Preferably, the content is 0.7 g / m or less. ２ More preferably, it is:

[0031] The binder layer may contain a binder resin other than the resin (A). Examples of binder resins that can be contained in the binder layer include ethylene-vinyl acetate copolymer (EVA, containing 20 to 35 mol% of structural units derived from vinyl acetate), ethylene-acrylate copolymer (ethylene-ethyl acrylate copolymer, etc.), various rubbers and their derivatives (styrene-butadiene rubber (SBR), fluororubber, urethane rubber, ethylene-propylene-diene rubber (EPDM)), cellulose derivatives (carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxypropyl cellulose, etc.), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), poly-N-vinylacetamide (PNVA), polyurethane, epoxy resin, polyvinylidene fluoride (PVDF), and vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP). One or more of these may be used.

[0032] When the binder resin is contained in the binder layer, the content of the binder resin is preferably 1 to 5 parts by mass per 100 parts by mass of the resin (A) in the binder layer.

[0033] The substrate layer of the separator is composed of a porous membrane. The porous membrane constituting the substrate layer can be a porous membrane made of a thermoplastic resin that is used as a separator in known electrochemical elements such as lithium-ion secondary batteries, more specifically, an ion-permeable porous membrane (microporous membrane) produced by a solvent extraction method, a dry or wet stretching method, or the like. Furthermore, a membrane in which an inorganic filler is held in the pores of a nonwoven fabric made of a thermoplastic resin can also be used as the porous membrane constituting the substrate layer.

[0034] That is, the porous film serving as the base layer is preferably composed mainly of a thermoplastic resin. In this case, when the temperature inside an electrochemical device using the separator rises to or exceeds the melting point of the thermoplastic resin that constitutes the base layer of the separator, the thermoplastic resin melts and blocks the pores of the separator, causing a shutdown that inhibits the progress of the electrochemical reaction, thereby improving the safety of the electrochemical device.

[0035] The melting point of the thermoplastic resin constituting the porous membrane that serves as the substrate layer varies depending on the shutdown temperature required in the electrochemical device, but is usually 140°C or lower. Examples of such thermoplastic resins include polyolefins such as polyethylene (PE) and ethylene-propylene copolymers. Therefore, the substrate layer is preferably a microporous membrane made of polyolefin.

[0036] When the porous membrane is mainly made of a thermoplastic resin having a melting point of 140° C. or less, the volume content of the main thermoplastic resin in the total volume of the constituent components of the porous membrane (total volume excluding pores) is 50% by volume or more, and more preferably 70% by volume or more. For example, when the porous membrane is made of a microporous PE membrane, the volume content of the thermoplastic resin (a resin having a melting point of 140° C. or less) is 100% by volume.

[0037] When the porous film used in the base layer is a microporous film made of a thermoplastic resin, the microporous film may contain various additives (such as an antioxidant) and an inorganic filler (such as the same inorganic particles as those of the fillers that can be used in the heat-resistant layer described below).

[0038] In addition, when the porous film used for the base layer contains a nonwoven fabric made of a thermoplastic resin and an inorganic filler held in the voids thereof, the inorganic filler can be the same as the inorganic particles among the fillers that can be used for the heat-resistant layer described later. In addition, when the porous film used for the base layer contains a nonwoven fabric made of a thermoplastic resin and an inorganic filler held in the voids thereof, a binder resin can be further contained to properly hold the inorganic filler in the voids of the nonwoven fabric, and the binder resin can be the same as the binder resin that can be used for the heat-resistant layer described later.

[0039] The thickness of the substrate layer (when the separator has multiple substrate layers, the total thickness of all substrate layers; details will be described later) is preferably 2 μm or more, more preferably 4 μm or more, and even more preferably 5 to 30 μm. The porosity of the substrate layer is preferably 35 to 80%.

[0040] The separator may be composed of only a substrate layer and a binder layer. In this case, the separator may have the binder layer on only one side of the substrate layer, or may have binder layers on both sides of the substrate layer, as necessary.

[0041] In addition to the substrate layer and the binder layer, the separator may also have a heat-resistant layer for improving the shape stability of the separator when the temperature in the electrochemical device rises. The separator having the heat-resistant layer can suppress the occurrence of a short circuit caused by the separator contracting and contacting the positive electrode and the negative electrode during shutdown, for example, thereby further improving the safety of the electrochemical device.

[0042] The heat-resistant layer preferably contains a filler having a heat resistance temperature of 150°C or higher, thereby ensuring heat resistance. In this specification, "a heat resistance temperature of 150°C or higher" means that no deformation such as softening is observed at least at 150°C.

[0043] The filler contained in the heat-resistant layer may be inorganic or organic particles as long as it has a heat-resistant temperature of 150°C or higher, is stable against the electrolyte of the electrochemical device, and is electrochemically stable and not easily oxidized or reduced within the operating voltage range of the electrochemical device. However, from the viewpoint of dispersion, fine particles are preferred, and inorganic oxide particles, more specifically, alumina, silica, and boehmite are preferred. Alumina, silica, and boehmite have high oxidation resistance and can be adjusted to desired particle sizes and shapes, making it easy to precisely control the porosity of the heat-resistant layer. Note that, as the filler having a heat-resistant temperature of 150°C or higher, for example, the above-exemplified ones may be used alone or in combination of two or more.

[0044] The amount of the filler in the heat-resistant layer is preferably 70% by volume or more, more preferably 80% by volume or more, and even more preferably 90% by volume or more, of the total volume of the components constituting the heat-resistant layer (total volume excluding pores). By setting the filler content in the heat-resistant layer to a high content as described above, it is possible to effectively suppress thermal shrinkage of the entire separator and impart high heat resistance.

[0045] In addition, it is preferable that the heat-resistant layer contains a binder resin to bond the fillers together and to bond the heat-resistant layer to the base layer. From this viewpoint, a suitable upper limit of the amount of the filler in the heat-resistant layer is, for example, 99% by volume of the total volume of the components of the heat-resistant layer. Note that if the amount of the filler in the heat-resistant layer is less than 70% by volume, for example, it becomes necessary to increase the amount of binder resin in the heat-resistant layer. In this case, however, the pores in the heat-resistant layer will be filled with the binder resin, which may impair the ion permeability in the separator.

[0046] The binder resin used in the heat-resistant layer is not particularly limited as long as it can provide good adhesion between the fillers and between the heat-resistant layer and the base layer, is electrochemically stable, and is stable against the electrolyte contained in the electrochemical element. Specific examples include fluororesins (such as PVDF), fluororubbers, SBR, CMC, hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), poly-N-vinylacetamide, acrylic resins (such as cross-linked acrylic resins), polyurethanes, and epoxy resins. These binder resins may be used alone or in combination of two or more.

[0047] When the separator has a heat-resistant layer, the heat-resistant layer may be only one layer or may be two or more layers (e.g., a heat-resistant layer on both sides of a substrate layer). In that case, the substrate layer may also be only one layer or may be two or more layers (e.g., a substrate layer on both sides of a heat-resistant layer). However, if the separator has too many layers, for example, the thickness of the entire separator may become too large, making it difficult to increase the capacity of the electrochemical device. Therefore, when the separator has a heat-resistant layer, it is preferable to have one heat-resistant layer on one side of one substrate layer, or one heat-resistant layer on each side of one substrate layer.

[0048] The thickness of the heat-resistant layer (when the separator has a plurality of heat-resistant layers, the total thickness of the heat-resistant layers) is preferably 1 μm or more, more preferably 2 μm or more, and is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 6 μm or less.

[0049] The total thickness of the separator is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more, and is preferably 30 μm or less, and more preferably 20 μm or less.

[0050] In producing the separator, for example, a method can be employed in which a binder layer-forming composition containing the resin (A) dispersed in a medium such as water or an organic solvent is applied to the surface of the substrate layer or the heat-resistant layer formed on the substrate layer, and then dried to form the binder layer. When the binder layer also contains a binder resin, the binder resin may be dispersed in water or an organic solvent, which is the medium of the binder layer-forming composition, or may be dissolved in these media.

[0051] Furthermore, when a separator having a heat-resistant layer is used, the heat-resistant layer can be formed, for example, by applying a heat-resistant layer-forming composition (slurry, paste, etc.) containing the filler, binder resin, etc. and a solvent (water, an organic solvent such as ketones, etc.) to a base layer and drying the composition.

[0052] The binder layer can be formed on the substrate layer, or in the case of a separator having a heat-resistant layer, on the heat-resistant layer, but the adhesive strength between the binder layer and the heat-resistant layer is likely to be greater than the adhesive strength between the binder layer and the substrate layer. Therefore, it is more preferable that the separator has a heat-resistant layer on one or both sides of the substrate layer and has a binder layer on the heat-resistant layer, which makes it possible to further increase the adhesive strength (peel strength) with the electrodes of the electrochemical element.

[0053] The separator preferably has an air permeability of 400 sec / 100 mL or less, more preferably 300 sec / 100 mL or less, from the viewpoint of improving the permeability of the liquid electrolyte (electrolytic solution) contained in the electrochemical device and thereby improving the characteristics of the electrochemical device. The separator also has an air permeability of 50 sec / 100 mL or more, more preferably 70 sec / 100 mL or more, and even more preferably 100 sec / 100 mL or more, from the viewpoint of increasing the strength of the separator to a certain extent, for example.

[0054] The air permeability of the separator referred to in this specification is a value determined by the Gurley method specified in JIS P 8117.

[0055] <Electrochemical element> The electrochemical element of the present invention has a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and it is sufficient that the separator is the separator for electrochemical elements of the present invention, and that at least one of the positive electrode and the negative electrode is bound to the separator by a binder layer of the separator. In other words, there are no particular limitations on the configuration and structure of the electrochemical element other than those described above, and various configurations and structures employed in known electrochemical elements such as lithium ion secondary batteries can be applied.

[0056] The electrochemical device of the present invention includes various primary batteries and secondary batteries (such as alkaline primary batteries, alkaline secondary batteries, and manganese batteries) having an aqueous electrolyte (such as an electrolytic solution); various primary batteries and secondary batteries (such as nonaqueous electrolyte primary batteries, and nonaqueous electrolyte secondary batteries such as lithium primary batteries) having a nonaqueous electrolyte (such as a nonaqueous electrolyte solution); and supercapacitors having a nonaqueous electrolyte solution.

[0057] In the electrochemical element of the present invention, at least one of the positive electrode and the negative electrode is bound to the separator by a binder layer provided on the separator. This prevents the gap between the positive electrode and the negative electrode from changing or fluctuating locally even if the volume of the electrodes changes during use of the electrochemical element, thereby maintaining good performance of the electrochemical element. Note that, in the present invention, either one of the positive electrode or the negative electrode may be bound to the separator, but from the viewpoint of maintaining good performance of the electrochemical element, it is preferable that both the positive electrode and the negative electrode are bound to the separator.

[0058] The electrochemical device of the present invention will be described in detail below by taking as an example a non-aqueous electrolyte secondary battery, which is a typical embodiment of the electrochemical device of the present invention.

[0059] The positive electrode of the nonaqueous electrolyte secondary battery may have a structure in which a positive electrode mixture layer containing a lithium-containing transition metal oxide as a positive electrode active material, a binder, a conductive additive, etc. is provided on one or both sides of a current collector.

[0060] Specific examples of the lithium-containing transition metal oxide that is the positive electrode active material include LiM ｘ Mn ２－ｘ O ４ (wherein M is at least one element selected from the group consisting of Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, Sb, In, Nb, Mo, W, Y, Ru, and Rh, and 0.01≦x≦0.5), a spinel-type lithium manganese composite oxide represented by Li ｘ Mn （１－ｙ－ｘ） Ni ｙ M ｚ O （２－ｋ） Fｌ (wherein M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and 0.8≦x≦1.2, 0<y<0.5, 0≦z≦0.5, k+l<1, −0.1≦k≦0.2, 0≦l≦0.1), a layered compound represented by １－ｘ M ｘ O ２ (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), lithium cobalt composite oxide represented by LiNi １－ｘ M ｘ O ２ (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), a lithium nickel composite oxide represented by LiM １－ｘ N ｘ O ２ (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦0.5), and the like. Only one of these may be used, or two or more may be used in combination.

[0061] As the binder for the positive electrode, for example, a fluororesin such as PVDF is used, and as the conductive additive for the positive electrode, for example, a carbon material such as carbon black is used.

[0062] The positive electrode can be manufactured, for example, by dispersing a positive electrode mixture containing a positive electrode active material, a conductive additive, and a binder in a solvent such as N-methyl-2-pyrrolidone (NMP) to prepare a positive electrode mixture-containing composition (slurry, paste, etc.), applying this to a current collector, drying it, and further subjecting it to a pressing process such as calendaring, as necessary. However, the method for manufacturing the positive electrode is not limited to the above method, and it may be manufactured by other methods.

[0063] As the current collector for the positive electrode, a foil of a metal such as aluminum, a punched metal, a mesh, an expanded metal, etc. can be used, but usually, an aluminum foil having a thickness of 10 to 30 μm is preferably used.

[0064] The lead portion on the positive electrode side is usually provided by leaving an exposed portion of the current collector without forming a positive electrode mixture layer on it during the preparation of the positive electrode, and using this exposed portion as the lead portion. However, the lead portion does not necessarily have to be integral with the current collector from the beginning, and may be provided by connecting an aluminum foil or the like to the current collector later.

[0065] The negative electrode of the non-aqueous electrolyte secondary battery is not particularly limited as long as it is a negative electrode used in known lithium ion secondary batteries, i.e., a negative electrode containing an active material capable of absorbing and releasing Li ions. For example, the active material may be one or a mixture of two or more carbonaceous materials capable of absorbing and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesophase carbon microbeads (MCMB), and carbon fibers. Also, compounds capable of charging and discharging at low voltages close to that of lithium metal, such as simple substances, compounds and alloys thereof, lithium-containing nitrides, or oxides containing elements such as Si, Sn, Ge, Bi, Sb, and In, or lithium metal, lithium / aluminum alloys, and even Li ４ Ti ５ O １２ A negative electrode mixture obtained by appropriately adding a conductive additive (carbon material such as carbon black) or a binder such as PVDF to such a negative electrode active material is formed into a compact (negative electrode mixture layer) using a current collector as a core material, for example, by the same method as the above-mentioned method for forming the positive electrode mixture layer, or a foil of any of the above-mentioned various alloys or lithium metal is used alone or laminated on a current collector as a negative electrode mixture layer.

[0066] When a current collector is used for the negative electrode, copper or nickel foil, punched metal, mesh, expanded metal, etc. can be used as the current collector, but copper foil is usually used. When the overall thickness of the negative electrode is reduced to obtain an electrochemical element with a high energy density, the upper limit of the thickness of this negative electrode current collector is preferably 30 μm, and the lower limit is desirably 5 μm. Furthermore, the lead portion on the negative electrode side may be formed in the same manner as the lead portion on the positive electrode side.

[0067] The positive electrode and the negative electrode are stacked with the separator of the present invention interposed therebetween, and can be used in the form of a laminated electrode body in which at least one of the positive electrode and the negative electrode is bound to the separator, or in the form of a wound electrode body in which the laminated electrode body is wound. After forming the wound electrode body, the electrode and the separator can also be bound by applying pressure to the wound electrode body.

[0068] The non-aqueous electrolyte of the non-aqueous electrolyte secondary battery can be a solution (non-aqueous electrolyte solution) in which a lithium salt is dissolved in an organic solvent. ＋ There are no particular limitations as long as the material forms ions and is unlikely to undergo side reactions such as decomposition within the voltage range used in the electrochemical element. For example, LiClO ４ , LiPF ６ , LiBF ４ , LiAsF ６ , LiSbF ６ Inorganic lithium salts such as LiCF ３ SO ３ , LiCF ３ CO ２ , Li ２ C ２ F ４ (SO ３ ) ２ , LiN(CF ３ SO ２ ) ２ , LiC(CF ３ SO ２ ) ３ , LiC ｎ F ２ｎ＋１ SO ３ (n≧2), LiN(R ｆ OSO ２ ) ２ [Here, R ｆor a fluoroalkyl group]; or an organic lithium salt such as

[0069] The organic solvent used in the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause side reactions such as decomposition within the voltage range used in the electrochemical element. Examples include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; chain ethers such as dimethoxyethane, diethyl ether, 1,3-dioxolane, diglyme, triglyme, and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile, and methoxypropionitrile; and sulfites such as ethylene glycol sulfite. These may also be used in combination of two or more.

[0070] The concentration of this lithium salt in the non-aqueous electrolyte is preferably 0.5 to 1.5 mol / L, and more preferably 0.9 to 1.25 mol / L.

[0071] Furthermore, the non-aqueous electrolyte may be a gel (gel electrolyte) prepared by adding a gelling agent such as a known polymer.

[0072] The electrochemical element of the present invention, including the nonaqueous electrolyte secondary battery, may have a cylindrical shape (e.g., rectangular or cylindrical) using a steel can or an aluminum can as an outer can. It may also be a soft-packaged element using a metal-deposited laminate film as an outer casing.

[0073] In addition, when the positive electrode or negative electrode is a mixture layer containing an active material (positive electrode mixture layer or negative electrode mixture layer), the binding strength with the separator can be further increased. This is presumably because, since the mixture layer of the positive electrode or negative electrode is porous, the particulate resin (A) contained in the binder layer of the separator is pushed into recesses such as voids on the surface, thereby exhibiting an excellent anchoring effect.

[0074] The electrochemical element of the present invention can be manufactured, for example, by a method including a step of laminating a positive electrode, a negative electrode, and a separator to form an electrode assembly (e.g., a laminated electrode assembly, a wound electrode assembly, etc.), and a step of encapsulating the electrode assembly obtained by this step in an outer casing together with an electrolyte. In the step of forming the electrode assembly, at least one of the positive electrode and the negative electrode is superimposed on the separator, and the binder layer of the separator is bonded to the electrode. During this bonding, pressure is applied at a temperature at which the resin (A) contained in the binder layer does not melt. That is, the pressure for bonding the binder layer of the separator to the electrode can be applied without heating, for example, at room temperature. However, pressure may also be applied while heating, for example, at a temperature at which the resin (A) does not melt, such as at 70°C or below.

[0075] As described above, the separator of the present invention can increase the bonding strength with the electrode by applying pressure without heating, and for example, the peel strength between the separator and the electrode can be increased to 0.4 N / m or more, preferably 1.0 N / m or more. There is no particular upper limit to the peel strength between the separator and the electrode, but it is usually about 5.0 N / m.

[0076] The peel strength between the separator and the electrode referred to in this specification is a value measured by the following method. A separator was cut to a length of 110 mm in the machine direction and a width of 20 mm in the transverse direction to prepare a test piece. The test piece was placed on top of the composite layer of an electrode sheet cut to 110 mm x 25 mm, with the adhesive layer of the test piece facing the composite layer, and the piece was placed in a hand press pre-adjusted to a predetermined temperature. The overlapping portion of the test piece and the electrode was adjusted to a length of 10 cm, and the set test piece was held under a predetermined load for a predetermined time to bond the test piece and the electrode, preparing a sample for peel strength measurement. Next, the electrode side of the sample was attached to a stainless steel plate (SUS plate) using double-sided adhesive tape (Nitto Denko Corporation, N5605). Furthermore, to facilitate attachment to the tensile tester, gummed tape was attached in a U-shape to one end of the test piece (separator) that was not overlapped with the electrode, and the SUS plate was then placed in a tensile tester (Minebea Co., Ltd.: TGE-10kN), and the gummed tape portion was pulled for 24 seconds at a tensile direction of 90° and a tensile speed of 200 mm / min, and the adhesive strength with the electrode (the average value of the peel force in the peel force curve obtained by the test) was measured. Each sample was measured three times, and the average value of these adhesive strengths was taken as the peel strength between the separator and electrode.

[0077] The temperature, load and holding time when bonding the test piece and the electrode may be set to the conditions in the actual manufacturing process of the electrochemical element.

[0078] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0079] Example 1 <Separator Preparation> 5 kg of powder containing aggregates of plate-like boehmite (average primary particle size of 1 μm, aspect ratio of 10) was mixed with 5 kg of ion-exchanged water and 0.5 kg of dispersant (aqueous polycarboxylic acid ammonium salt, solids concentration of 40% by mass), and the mixture was crushed for 10 hours in a ball mill with an internal volume of 20 L and a rotation speed of 40 rpm to prepare a dispersion. A portion of the dispersion after the treatment was vacuum-dried at 120°C and observed with a scanning electron microscope (SEM). The boehmite was found to have an almost plate-like shape. Furthermore, the average particle size of the boehmite after the treatment was 1 μm, confirming that the crushing had been sufficiently performed.

[0080] To 500 g of the dispersion, 0.5 g of xanthan gum as a thickener and 17 g of a resin binder dispersion (containing modified polybutyl acrylate and PNVA in a mass ratio of 2:1, with a solid content of 45% by mass) were added, and the mixture was stirred for 3 hours using a mixer "Three One Motor" (product name) manufactured by Shinto Scientific Co., Ltd. to prepare a uniform slurry for forming a heat-resistant layer (solid content ratio: 50% by mass).

[0081] A polyolefin microporous laminated film (total thickness 12 μm, porosity 50%) was used as the substrate layer. The film had an intermediate layer made of polyethylene with a thickness of 4 μm and outer layers made of polypropylene with a thickness of 4 μm laminated on both sides. Both sides of the substrate layer were subjected to corona discharge treatment (discharge amount 40 W min / m ２ The slurry for forming a heat-resistant layer was applied to the treated surface using a microgravure coater and dried to form heat-resistant layers on both sides of the base layer. The thickness of the heat-resistant layer on both sides was 1.9 μm.

[0082] Next, a water dispersion of a propylene-based polymer ("Chemipearl (registered trademark) EP151H" manufactured by Mitsui Chemicals, Inc., melting point of resin (A) 80°C, average particle size of resin (A) 0.4 μm) was used as a binder layer-forming composition containing resin (A). This was applied to one of the heat-resistant layers formed on both sides of the base layer so that the weight of resin (A) after drying was 0.4 g / m ２ The mixture was applied so that the resin (A) was in a particle form and then dried to obtain a separator having a binder layer made of the particulate resin (A) on one side.

[0083] <Measurement of Air Permeability (Initial)> The produced separator was cut into a size of 5 cm x 5 cm, and the air permeability was measured using the Oken testing machine method described in JIS P8117:2009. The average value of the air permeabilities of the separator cut out at three locations was taken as the initial air permeability of the separator. The measured initial air permeability was 205 seconds / 100 mL.

[0084] <Preparation of Positive Electrode> The positive electrode active material LiMn １．５ Ni ０．５ O ４85 parts by weight, acetylene black as a conductive additive, 10 parts by weight, and PVDF as a binder, 5 parts by weight, were mixed uniformly using NMP as a solvent to prepare a positive electrode mixture-containing paste. This paste was intermittently applied to both sides of an aluminum foil having a thickness of 15 μm as a current collector, dried, and then calendered to adjust the thickness of the positive electrode mixture layer so that the total thickness was 150 μm. The positive electrode mixture layer was cut into a shape having a width of 105 mm and a length of 200 mm, and having an exposed portion of the positive electrode current collector. A tab was welded to the exposed portion of the aluminum foil to form a lead portion to prepare a positive electrode. The prepared positive electrode was cut to a predetermined size and used for measuring the air permeability (after bonding) and peel strength, which will be described later.

[0085] <Preparation of negative electrode> 95 parts by mass of graphite as a negative electrode active material and 5 parts by mass of PVDF as a binder were mixed uniformly using NMP as a solvent to prepare a negative electrode mixture-containing paste. This negative electrode mixture-containing paste was intermittently applied to both sides of a 10 μm thick copper foil current collector, dried, and then calendered to adjust the thickness of the negative electrode mixture layer so that the total thickness was 142 μm. The negative electrode mixture layer was cut into a shape with a width of 110 mm and a length of 205 mm, and an exposed portion of the negative electrode current collector. A tab was welded to the exposed portion of the copper foil to form a lead portion to prepare a negative electrode. In addition, for the measurement of peel strength described below, the prepared negative electrode was cut to a predetermined size and used.

[0086] <Air permeability measurement (after bonding)> The prepared separator was cut into a size of 50 mm x 50 mm, and PTFE sheets 50 μm thick, larger than the separator, were placed on both sides of the separator. The separator's binder layer was placed on the positive electrode cut into a size of 50 mm x 50 mm, with the binder layer facing the positive electrode side. The entire separator was pressed with a load of 3.9 MPa for 10 seconds to crush the binder layer. The binder layer in this state was considered to be bonded to the positive electrode, and the separator was peeled from the PTFE sheet and the separator cut out at three locations was measured for each of the permeabilities in the same manner as above. The average value was used as the permeability of the separator after bonding. The measured permeability after bonding was 220 seconds / 100 mL.

[0087] <Measurement of Peel Strength> (Measurement 1-1) The separator was cut to a length of 110 mm in the MD direction and a width of 20 mm in the TD direction, and the positive electrode was further cut to a size of 110 mm x 25 mm, and then a sample for measuring peel strength was prepared by the method described above. Note that the temperature of the hand press during bonding was set to 25°C, the load was set to 3.9 MPa, and the holding time was set to 10 seconds to bond the positive electrode and the separator.

[0088] The peel strength between the positive electrode and the separator was measured by the above-mentioned method using the prepared sample for measuring peel strength, and was found to be 1.3 N / m.

[0089] (Measurement 1-2) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-1, except that the load when bonding the positive electrode and the separator was 6.4 MPa and the holding time was 60 seconds. The peel strength between the positive electrode and the separator was measured and found to be 4.2 N / m.

[0090] (Measurement 1-3) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-1, except that the load when bonding the positive electrode and the separator was 17.7 MPa. The peel strength between the positive electrode and the separator was measured and found to be 7.6 N / m.

[0091] (Measurement 1-4) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-1, except that the negative electrode was cut into a size of 110 mm x 25 mm and used instead of the positive electrode, and the negative electrode and separator were bonded together using a hand press at a temperature of 25°C, a load of 3.9 MPa, and a holding time of 10 seconds. The peel strength between the negative electrode and the separator was measured using the prepared sample for measuring peel strength by the method described above, and was found to be 0.9 N / m.

[0092] (Measurement 1-5) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-4, except that the load when bonding the negative electrode and the separator was 6.4 MPa and the holding time was 60 seconds. The peel strength between the negative electrode and the separator was measured and found to be 3.7 N / m.

[0093] (Measurement 1-6) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-1, except that the temperature when bonding the positive electrode and the separator was 70°C and the load was 2.5 MPa. The peel strength between the positive electrode and the separator was measured and found to be 6.6 N / m.

[0094] (Measurement 1-7) A sample for measuring peel strength was prepared in the same manner as in Measurement 1-4, except that the temperature when bonding the negative electrode and the separator was 70°C and the load was 2.5 MPa. The peel strength between the negative electrode and the separator was measured and found to be 7.4 N / m.

[0095] Example 2 The binder layer-forming composition used in Example 1 was dried to a resin (A) weight of 0.2 g / m ２ and 0.6 g / m ２ Two types of separators having different bonding layers with different basis weights were obtained in the same manner as in Example 1, except that the coating was performed so that the bonding layer had a different basis weight.

[0096] <Measurement of peel strength> (Measurement 2-1) After drying, the weight of the resin (A) was 0.2 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 4.5 N / m.

[0097] (Measurement 2-2) The weight of the resin (A) after drying was 0.6 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 9.2 N / m.

[0098] Example 3 A separator having a binder layer made of particulate resin (A) on one side was obtained in the same manner as in Example 1, except that a binder layer-forming composition containing resin (A) was used in which the resin binder dispersion used in Example 1 was added in an amount of 6.7 parts by mass (containing 2 parts by mass of modified polybutyl acrylate and 1 part by mass of PNVA) to 100 parts by mass of the aqueous dispersion of the propylene-based polymer used in Example 1.

[0099] <Measurement of Peel Strength> (Measurement 3-1) The peel strength between the positive electrode and the separator obtained was measured in the same manner as in Measurement 1-2 of Example 1, and was found to be 6.0 N / m.

[0100] The air permeability of the separator was measured, and it was found that the initial air permeability was 210 seconds / 100 mL and the air permeability after bonding with the positive electrode was 220 seconds / 100 mL.

[0101] (Measurement 3-2) The peel strength between the negative electrode and the separator obtained was measured in the same manner as in Measurement 1-5 of Example 1, and was found to be 5.8 N / m.

[0102] Example 4 A separator having a binder layer made of particulate resin (A) on one side was obtained in the same manner as in Example 1, except that an aqueous dispersion of an ethylene polymer ("CHEMIPEARL (registered trademark) W700" manufactured by Mitsui Chemicals, Inc., melting point of resin (A) 127°C, average particle size of resin (A) 1 μm) was used as the binder layer-forming composition containing resin (A).

[0103] <Measurement of Peel Strength> (Measurement 4-1) The peel strength between the positive electrode and the separator obtained was measured in the same manner as in Measurement 1-1 of Example 1, and was found to be 0.6 N / m.

[0104] (Measurement 4-2) For the obtained separator, a sample for measuring peel strength was prepared in the same manner as in Measurement 4-1, except that the load when bonding the positive electrode and the separator was 6.4 MPa and the holding time was 60 seconds. The peel strength between the positive electrode and the separator was measured and found to be 1.5 N / m.

[0105] (Measurement 4-3) For the obtained separator, a sample for measuring peel strength was prepared in the same manner as in Measurement 4-1, except that the load when bonding the positive electrode and the separator was 17.7 MPa, and the peel strength between the positive electrode and the separator was measured, and it was 2.5 N / m.

[0106] Example 5 The binder layer-forming composition used in Example 4 was dried to a resin (A) weight of 0.2 g / m ２A separator having a binder layer made of particulate resin (A) on one side was obtained in the same manner as in Example 1, except that the coating was performed so that the binder layer was made of particulate resin (A).

[0107] <Measurement of Peel Strength> (Measurement 5-1) The peel strength between the positive electrode and the separator obtained was measured in the same manner as in Measurement 4-3 of Example 4, and was found to be 1.2 N / m.

[0108] Example 6 As a binder layer-forming composition containing resin (A), an aqueous dispersion of an ethylene polymer ("Chemipearl (registered trademark) W401" manufactured by Mitsui Chemicals, Inc., melting point of resin (A) 109°C, average particle size of resin (A) 1 μm) was used, and this was applied to one of the heat-resistant layers formed on both sides of the base layer so that the weight of resin (A) after drying was 0.2 g / m ２ and 0.4 g / m ２ Two types of separators having different bonding layers with different basis weights were obtained in the same manner as in Example 1, except that the coating was performed so that the bonding layer had a thickness of 1 / 2 mm.

[0109] <Measurement of Peel Strength> (Measurement 6-1) After drying, the weight of the resin (A) was 0.2 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 2.7 N / m.

[0110] (Measurement 6-2) The weight of the resin (A) after drying was 0.4 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 5.7 N / m.

[0111] Example 7 As a binder layer-forming composition containing resin (A), an aqueous dispersion of an ethylene polymer ("Chemipearl (registered trademark) W4005" manufactured by Mitsui Chemicals, Inc., melting point of resin (A) 108°C, average particle size of resin (A) 0.6 µm) was used, and this was applied to one of the heat-resistant layers formed on both sides of the base layer so that the basis weight of resin (A) after drying was 0.05 g / m ２ and 0.4 g / m ２ Two types of separators having different bonding layers with different basis weights were obtained in the same manner as in Example 1, except that the coating was performed so that the bonding layer had a thickness of 1 / 2 mm.

[0112] <Measurement of peel strength> (Measurement 7-1) After drying, the weight of the resin (A) was 0.05 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 2.3 N / m.

[0113] (Measurement 7-2) The weight of the resin (A) after drying was 0.4 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 6.6 N / m.

[0114] Example 8 As a binder layer-forming composition containing resin (A), an aqueous dispersion of an ethylene polymer ("Chemipearl (registered trademark) W900" manufactured by Mitsui Chemicals, Inc., melting point of resin (A) 125°C, average particle size of resin (A) 0.6 µm) was used, and this was applied to one of the heat-resistant layers formed on both sides of the base layer so that the weight of resin (A) after drying was 0.05 g / m ２ , 0.2 g / m ２ and 0.4 g / m ２ Three types of separators having different basis weights of the binder layer were obtained in the same manner as in Example 1, except that the coating was performed so that the binder layer had a basis weight of 10 ...

[0115] <Measurement of Peel Strength> (Measurement 8-1) After drying, the weight of the resin (A) was 0.05 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 1.3 N / m.

[0116] (Measurement 8-2) The weight of the resin (A) after drying was 0.2 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 2.0 N / m.

[0117] (Measurement 8-3) The weight of the resin (A) after drying was 0.4 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 7.1 N / m.

[0118] Example 9 As a binder layer-forming composition containing resin (A), an aqueous dispersion of an ethylene polymer ("AB-50" manufactured by Gifu Ceramics Manufacturing Co., Ltd., melting point of resin (A) 125°C, average particle size of resin (A) 1 μm) was used, and this was applied to one of the heat-resistant layers formed on both sides of the base layer so that the basis weight of resin (A) after drying was 0.05 g / m ２ , 0.1 g / m ２ and 0.2 g / m ２ Three types of separators having different basis weights of the binder layer were obtained in the same manner as in Example 1, except that the coating was performed so that the binder layer had a basis weight of 10 ...

[0119] <Measurement of Peel Strength> (Measurement 9-1) After drying, the weight of the resin (A) was 0.05 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 0.6 N / m.

[0120] (Measurement 9-2) The weight of the resin (A) after drying was 0.1 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 0.9 N / m.

[0121] (Measurement 9-3) The weight of the resin (A) after drying was 0.2 g / m ２ The peel strength between the positive electrode and the separator was measured in the same manner as in Measurement 1-3 of Example 1, and was found to be 2.5 N / m.

[0122] Comparative Example 1 A separator having no adhesive layer formed on the surface and heat-resistant layers formed on both sides of the base material layer was used as is, and an attempt was made to bond the two by overlapping it with a positive electrode in the same manner as in Measurement 1-1 of Example 1, but no bonding occurred and the peel strength was 0 N / m. Furthermore, when an attempt was made to bond it with a negative electrode in the same manner as in Measurement 1-4 of Example 1, the result was the same as in the case of the positive electrode, and the peel strength was 0 N / m.

[0123] The initial air permeability of the separator of Comparative Example 1 was 185 seconds / 100 mL, and the air permeability after being pressed together with the PTFE sheet and the positive electrode, measured in the same manner as in Example 1, was 190 seconds / 100 mL.

[0124] Comparative Example 2 A separator having a binder layer made of particulate PVDF on one side was obtained in the same manner as in Example 1, except that an aqueous dispersion of PVDF particles having an average particle size of 0.4 μm was used as the binder layer-forming composition.

[0125] <Measurement of Peel Strength> (Measurement 2C-1) The peel strength between the positive electrode and the separator obtained was measured in the same manner as in Measurement 1-1 of Example 1, and was found to be 0.2 N / m.

[0126] (Measurement 2C-2) When the peel strength between the negative electrode and the separator obtained was measured in the same manner as in Measurement 1-4 of Example 1, it was found to be approximately 0 N / m.

[0127] The configurations of the binder layers [resin (A)] for the separators of Examples 1 to 9 and Comparative Examples 1 and 2 are shown in Table 1, and the preparation conditions (pressing conditions) of samples for measuring the peel strength between the electrode (positive electrode or negative electrode) and the separator and the measurement results of the peel strength are shown in Table 2.

[0128]

[0129]

[0130] Example 10 <Preparation of separator> In the same manner as in Example 1, heat-resistant layers were formed on both sides of the base material layer, and the weight of the resin (A) after drying was 0.4 g / m ２ This separator was cut into a size of 115 mm x 220 mm and used for assembling a battery.

[0131] <Assembly of Battery> The positive electrode and negative electrode prepared in Example 1 and the separator were stacked together such that the mixture layers of the positive electrode and negative electrode faced the separator, respectively, and pressurized at a pressure of 3.9 MPa for 10 seconds in an environment of 25°C to bond the positive electrode, negative electrode and separator together, thereby obtaining a laminated electrode body.

[0132] The outer casing was two 150 μm thick metal laminate films (rectangular, 130 mm × 240 mm) with a three-layer structure consisting of polyester film / aluminum film / modified polyolefin film. The laminated electrode body and the non-aqueous electrolyte solution were mixed in a solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1:2, and LiPF ６ A solution in which the above was dissolved at a concentration of 1.2 mol / L was sealed in the exterior body, thereby obtaining a nonaqueous electrolyte secondary battery having the appearance shown in FIG. 2 and the structure shown in FIG.

[0133] 2 and 3, Fig. 2 is a plan view schematically illustrating a nonaqueous electrolyte secondary battery, and Fig. 3 is a cross-sectional view taken along line II in Fig. 2. The nonaqueous electrolyte secondary battery 100 contains a laminate film exterior body 400 made of two metal laminate films, a laminate electrode assembly 500, and an electrolyte (a nonaqueous electrolyte solution, not shown). The laminate film exterior body 400 is sealed at its periphery by heat-sealing the upper and lower laminate films. Note that in Fig. 3, in order to avoid complicating the drawing, the layers constituting the laminate film exterior body 400, as well as the positive electrodes, negative electrodes, and separators constituting the laminate electrode assembly 500, are not distinguished from one another.

[0134] The positive electrode constituting the laminated electrode body 500 is connected to the positive electrode external terminal 200 by a tab within the battery 100, and although not shown, the negative electrode constituting the laminated electrode body 500 is also connected to the negative electrode external terminal 300 by a tab within the battery 100. One end of the positive electrode external terminal 200 and the negative electrode external terminal 300 is drawn out to the outside of the laminated film exterior body 400 so that they can be connected to external devices, etc.

[0135] Comparative Example 3 A non-aqueous electrolyte secondary battery was obtained in the same manner as in Example 10, except that the same separator as in Comparative Example 1 was used.

[0136] The nonaqueous electrolyte secondary batteries of Example 10 and Comparative Example 3 were charged at a constant current of 600 mA up to 4.2 V, and then further charged at a constant voltage of 4.2 V up to a current value of 10 mA, and then discharged at a current value of 600 mA down to 2.5 V, and the discharge capacity (standard capacity) was measured.

[0137] Next, after charging under the above conditions, the battery was discharged at a current of 3 A until the voltage reached 2.5 V, and the discharge capacity (large current capacity) was measured. The ratio of the large current capacity to the standard capacity was calculated as the load characteristic. The results are shown in Table 3.

[0138]

[0139] The nonaqueous electrolyte secondary battery of Example 10, which used the separator of the present invention provided with a binder layer, had load characteristics almost the same as those of the nonaqueous electrolyte secondary battery of Comparative Example 3, which used a conventional separator without a binder layer. As is clear from these results, the separator of the present invention provided with a binder layer showed little deterioration in load characteristics due to the binder layer, and a nonaqueous electrolyte secondary battery with excellent characteristics could be constructed.

[0140] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0141] The electrochemical element of the present invention can be used in the same applications as those in which known electrochemical elements such as lithium ion secondary batteries are used. Furthermore, the separator for an electrochemical element of the present invention can constitute the electrochemical element of the present invention.

[0142] By applying the separator for electrochemical elements of the present invention to an electrochemical element, it is possible to contribute to the achievement of Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable and modern energy for all), Goal 11 (Make cities and human settlements inclusive, safe, resilient and sustainable), and Goal 12 (Ensure sustainable consumption and production patterns) out of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0143] REFERENCE SIGNS LIST 10 Separator for electrochemical element 11 Base material layer 12 Heat-resistant layer 13 Binder layer 20 Positive electrode 30 Negative electrode 100 Non-aqueous electrolyte secondary battery (electrochemical element) 200 Positive electrode external terminal 300 Negative electrode external terminal 400 Laminated film outer casing 500 Laminated electrode body

Claims

1. A separator for an electrochemical element having a substrate layer made of a porous film and a binder layer for bonding electrodes of an electrochemical element, wherein the binder layer contains a particulate resin (A), the melting point of the resin (A) is 75 to 140°C, and the basis weight of the resin (A) in the binder layer is 0.05 g / m ２ A separator for an electrochemical element characterized by the above.

2. The basis weight of the resin (A) in the binder layer is 0.2 g / m ２ The separator for an electrochemical element according to claim 1 .

3. The basis weight of the resin (A) in the binder layer is 0.9 g / m ２ 2. The separator for an electrochemical element according to claim 1, wherein:

4. The separator for an electrochemical element according to claim 1, wherein the resin (A) has an average particle size of 0.2 to 3 μm.

5. The separator for an electrochemical element according to claim 1, which has an air permeability of 50 to 400 sec / 100 mL.

6. The separator for an electrochemical element according to claim 1, wherein the resin (A) contains a polymer having a structural unit derived from ethylene or propylene.

7. The separator for an electrochemical element according to claim 6, wherein the binder layer contains a binder resin different from the resin (A).

8. The separator for an electrochemical element according to claim 1, wherein one or both surfaces of the substrate layer have a heat-resistant layer containing a filler having a heat-resistant temperature of 150° C. or higher.

9. The separator for an electrochemical element according to claim 8, wherein the adhesive layer is provided on the heat-resistant layer.

10. The separator for an electrochemical element according to claim 1, wherein the substrate layer is a microporous film made of polyolefin.

11. An electrochemical element having a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, wherein the separator is a separator for electrochemical elements according to any one of claims 1 to 10, and at least one of the positive electrode and the negative electrode is bound to the separator by the binding layer of the separator.

12. The electrochemical element according to claim 11, wherein the peel strength between the separator and the electrode bound to the separator by the binding layer is 0.4 N / m or more.

13. The electrochemical element according to claim 11, wherein the electrode bound to the separator by the binder layer has a mixture layer containing an active material.

14. A method for producing an electrochemical element having a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, comprising the steps of: using a separator for electrochemical elements according to any one of claims 1 to 10 as the separator; and overlapping at least one of the positive electrode and the negative electrode with the separator; and applying pressure at a temperature at which the resin (A) does not melt, thereby bonding the electrodes and the separator.