JP6993277B2 - Insulation layer forming composition, electrochemical element electrode body, and electrochemical element - Google Patents

Description

The present invention is a composition for forming an insulating layer suitable for forming an insulating layer of an electrode body for an electrochemical element having a sulfide-based solid electrolyte, and an electrochemical element having an insulating layer formed by the composition for forming an insulating layer. The present invention relates to an electrode body for use and an electrochemical element having the electrode body for the electrochemical element.

Non-water secondary batteries are widely used as a power source for mobile devices such as smartphones and notebook personal computers, and are also being applied to in-vehicle applications and industrial applications. Therefore, the non-aqueous secondary battery is required to have high safety in response to such widespread use.

In a non-aqueous secondary battery, it is common to use a microporous film (microporous film) made of polyolefin such as polyethylene as a separator. Such a microporous film is usually produced through a step of uniaxial stretching or biaxial stretching, but since strain is generated by stretching, shrinkage is likely to occur when exposed to high temperature. If the inside of the non-aqueous secondary battery becomes hot and the separator shrinks, the positive electrode and the negative electrode may come into direct contact with each other to cause a short circuit.

As a countermeasure against such a problem, for example, a non-aqueous secondary battery having an electrode body formed by inserting a positive electrode into a bag-shaped separator made of polyolefin and laminating a negative electrode therein has been developed (Patent Document). 1 etc.). When a bag-shaped separator is used, the two separators wrapping the positive electrode are bonded to each other, so that the separator does not easily shrink even at high temperatures, and thus it is possible to improve the safety of the non-aqueous secondary battery. It becomes.

Further, studies have been made to improve the safety of non-aqueous secondary batteries by arranging a solid electrolyte between the positive electrode and the negative electrode and in the positive electrode and the negative electrode instead of the separator and the liquid non-aqueous electrolyte (). Patent Documents 2, 3, etc.).

Japanese Unexamined Patent Publication No. 2011-113826 Japanese Unexamined Patent Publication No. 2017-40531 Japanese Unexamined Patent Publication No. 2017-168387

However, in a battery having an electrode body in which a solid electrolyte (solid electrolyte layer) is arranged between a positive electrode and a negative electrode, the area of the solid electrolyte may be substantially the same as the area of the positive electrode and the negative electrode, unlike the case of a separator. Since it is general, there is a problem that a short circuit is likely to occur due to contact between the positive electrode and the negative electrode, especially when working on collecting electricity of the positive electrode and the negative electrode when forming the electrode body.

The present invention has been made in view of the above circumstances, and an object thereof is a composition capable of satisfactorily forming an insulating layer for preventing short circuits of an electrochemical element using a sulfide-based solid electrolyte. It is an object of the present invention to provide an electrode body for an electrochemical element having a formed insulating layer, and an electrochemical element having the electrode body.

The composition for forming an insulating layer of the present invention is used for forming an insulating layer in an electrochemical element having a solid electrolyte layer containing a sulfide-based solid electrolyte, and has a melting point or a thermal decomposition temperature of 150 ° C. It contains a filler containing the above resin, a binder, and a solvent having a solubility parameter of 8.8 to 9.5, and the content of the binder is 15 parts by mass or more with respect to 100 parts by mass of the filler. It is characterized by being.

Further, the electrode body for an electrochemical element of the present invention (hereinafter, simply referred to as “electrode body”) has a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and the solid. The electrolyte layer contains a sulfide-based solid electrolyte, and an insulating layer containing a filler containing a resin having a melting point or a thermal decomposition temperature of 150 ° C. or higher and a binder is formed on the side surface of the electrode body. It is a feature.

Further, the electrochemical element of the present invention includes an electrode body having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode, and the electrode body for the electrochemical element of the present invention is the electrode body. It is characterized by having a body.

According to the present invention, a composition capable of satisfactorily forming an insulating layer for preventing short circuits of an electrochemical element using a sulfide-based solid electrolyte, and an electrode body for an electrochemical element having an insulating layer formed by this composition. , And an electrochemical element having the electrode body can be provided.

It is a top view schematically showing an example of the electrode body for an electrochemical element of this invention. FIG. 1 is a cross-sectional view taken along the line II of FIG. It is sectional drawing which shows the example of the electrochemical element of this invention schematically.

1 and 2 show a diagram schematically showing an example of the electrode body of the present invention. FIG. 1 is a plan view of the electrode body 100, and FIG. 2 is a sectional view taken along line II of FIG.

The electrode body 100 shown in FIG. 2 is a laminated electrode body in which three unit units configured by laminating a positive electrode 20 and a negative electrode 30 via a solid electrolyte layer 40 are laminated.

The positive electrode 20 has a main body portion 20a in which a positive electrode mixture layer 21 is formed on one side of a positive electrode current collector 22, and a current collector tab portion 20b formed by an exposed portion of the positive electrode current collector 22. .. Further, the negative electrode 30 has a main body portion 30a in which the negative electrode mixture layer 31 is formed on one side of the negative electrode current collector 32, and a current collector tab portion 30b formed by the exposed portion of the negative electrode current collector 32. ing. Further, the solid electrolyte layer 40 contains a sulfide-based solid electrolyte.

The electrode body 100 is configured such that the unit units in which the positive electrode 20, the solid electrolyte layer 40, and the negative electrode 30 are laminated are laminated so that the positive electrodes 20 face each other and the negative electrodes 30 face each other. Has been done. Further, an insulating layer 50 is formed on the side surface of the electrode body 100 (that is, the end face of the positive electrode 20, the end face of the negative electrode 30, and the end face of the solid electrolyte layer 40).

In an electrode body related to an electrochemical element using a solid electrolyte instead of a separator and an electrolyte, since the solid electrolyte is hard and brittle, the positive electrode and the negative electrode and the solid electrolyte layer have substantially the same planar shape, and the positive electrode and the negative electrode are used. By sandwiching the entire solid electrolyte layer between them, the occurrence of defects such as cracks in the solid electrolyte layer in the electrochemical element is prevented. Therefore, unlike the case where an electrode body using a solid electrolyte has a planar shape larger than that of the electrode, for example, a short circuit is likely to occur at the end face of the positive electrode or the negative electrode due to contact with the other electrode. In particular, as shown in FIG. 2, the positive electrode and the negative electrode are electrically connected to each other in the electrode body and to the terminal portion (external terminal) of the electrochemical element together with the main body portion having the mixture layer containing the active material. When the current collecting tab portion used for the above is provided, contact between the current collecting tab portion of one electrode and the end face of the other electrode is likely to occur, and the occurrence of a short circuit due to such a reason can be suppressed. Desired.

Therefore, in the electrode body of the present invention, as shown in FIGS. 1 and 2, an insulating layer is formed on the side surface thereof, and the end faces of the positive electrode and the negative electrode are in contact with the other electrode (for example, the current collecting tab portion thereof). It is now possible to prevent the occurrence of a short circuit due to.

By the way, for forming an insulating layer in an electrode body, it is efficient to use a composition (paint) for forming an insulating layer prepared by dissolving or dispersing a material for forming the insulating layer in a solvent. However, since the electrode body of the present invention has a solid electrolyte layer containing a sulfide-based solid electrolyte, the composition for forming an insulating layer is required not to cause deterioration of the sulfide-based solid electrolyte. ..

Therefore, in the present invention, the insulating layer is formed by a composition (slurry, paste, etc.) in which the constituent material of the insulating layer is dispersed or dissolved in a solvent, and the solubility parameter (solubility parameter (solubility parameter) is used in the solvent of the composition for forming the insulating layer. It was decided to use a δ) of 8.8 or more and 9.5 or less. Since such a solvent has a low polarity and has a small effect on the sulfide-based solid electrolyte, even if an insulating layer is formed on the side surface of the electrode body by using a composition for forming an insulating layer containing the solvent. , It is possible to suppress deterioration of the characteristics of the electrochemical element using this electrode body.

Specific examples of the solvent of the composition for forming an insulating layer include xylene (δ = 8.8), methicylene (δ = 8.8), toluene (δ = 8.9), tetralin (δ = 9.5) and the like. However, it is possible to use only one of these, or two or more of them, but it is more preferable to use toluene.

Since the sulfide-based solid electrolyte is inferior in water resistance, it is preferable that the solvent of the insulating layer forming composition has a low water content, whereby the sulfide-based solid when the insulating layer forming composition is applied is applied. It is possible to better suppress the deterioration of the electrolyte. Specifically, the water content of the solvent is preferably 10 ppm or less, more preferably 5 ppm or less, and particularly preferably 0 ppm, that is, no water content, on a mass basis. As the solvent having a low water content, a commercially available solvent can be used.

The composition for forming an insulating layer contains a filler containing a resin having a melting point or a thermal decomposition temperature of 150 ° C. or higher, and the insulating layer formed by this composition has good heat resistance. An electrochemical element having a solid electrolyte instead of a separator and an electrolyte generally has good heat resistance, but even if an insulating layer is formed on the side surface of the electrode body by the insulating layer forming composition of the present invention, the insulating layer is used. Since the decrease in heat resistance of the electrochemical element can be suppressed, the heat resistance of the electrochemical element using the electrode body of the present invention (electrochemical element of the present invention) can be maintained satisfactorily.

The resin constituting the filler has a melting point (melting temperature measured according to JIS K 7121) or thermal decomposition temperature (10% weight reduction determined by thermal weight measurement measured according to JIS K 7120). There is no particular limitation as long as the temperature at the time is 150 ° C or higher, but specifically, polyolefin (polyetherketone, polymethylpentene, etc.), polyester (aromatic polyester typified by all-aromatic polyester, polybutylene terephthalate, etc.), etc. ), Polymethylmethacrylate (PMMA), Polyacetal, Polyamide [Aromatic polyamide represented by total aromatic polyamide (aramid), nylon, etc.], Polyether (Aromatic polyether represented by total aromatic polyether, etc.) ), Polyetherketone (aromatic polyketone represented by all aromatic polyketone, etc.), polyimide, polyamideimide, polyphenylene sulfide, polybenzoimidazole, polyetheretherketone, polyethersulfone, poly (para-phenylenebenzobisthiazole), poly (Para-phenylene-2,6-benzobisoxazole), polyurethane, cellulose, polyvinyl alcohol and the like can be used. The resin constituting the filler may be a crosslinked product.

For the filler, only one kind of particles composed of the above resin may be used, or two or more kinds may be used in combination. When a material having high hygroscopicity (for example, polyamide, polyimide, polyamideimide, cellulose, polyvinyl alcohol, etc.) is used, the amount of water brought into the electrochemical element may increase, so that polyolefin or polyester may be used. , PMMA and other materials with low hygroscopicity are preferably used, and PMMA (or a crosslinked product thereof) is more preferably used.

The average particle size of the filler is preferably 0.1 μm or more, more preferably 0.3 μm or more in order to maintain the moisture permeability of the insulating layer, and the heat resistance and adhesiveness of the insulating layer. It is preferably 1 μm or less, and more preferably 0.7 μm or less in order to achieve both.

For the average particle size of the filler, for example, a laser scattering particle size distribution meter (for example, “LA-920” manufactured by HORIBA) is used to disperse the filler in a medium in which the filler is not dissolved or swelled. It can be specified as the measured number average particle size (the average particle size shown in the examples described later is a value obtained by this method).

The composition for forming an insulating layer contains a binder for adhering the insulating layer to an electrode or a sulfide-based solid electrolyte, or for binding the fillers to each other. Specific examples of the binder include ethylene-vinyl acetate copolymer (EVA, which has a structural unit derived from vinyl acetate of 20 to 35 mol%) and acrylic resin (ethylene-acrylic acid such as ethylene-ethyl acrylate copolymer). Polymers, crosslinked acrylic resins, etc.), Fluorine rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), Examples thereof include polyurethane and epoxy resin, and in particular, a heat-resistant binder having a heat-resistant temperature of 150 ° C. or higher is preferably used. As the binder, only one of the above-exemplified ones may be used, or two or more of them may be used in combination, but it is more preferable to use an acrylic resin.

In the composition for forming an insulating layer, the content of the binder is preferably 15 parts by mass or more, preferably 20 parts by mass, based on 100 parts by mass of the filler content, from the viewpoint of enabling the insulating layer to be formed satisfactorily. The above is more preferable. However, if the amount of the binder in the composition for forming the insulating layer is too large, the amount of the filler in the insulating layer to be formed may be too small, and the heat resistance of the insulating layer may be lowered. Therefore, the content of the binder is preferably 60 parts by mass or less, and more preferably 55 parts by mass or less, based on 100 parts by mass of the filler.

The method for preparing the composition for forming an insulating layer is not particularly limited, and among various known mixing methods, a method capable of uniformly dispersing the filler in a solvent and uniformly dissolving or dispersing the binder in the solvent can be used. You can adopt it.

The solid content concentration (total content of the components excluding the solvent) of the composition for forming the insulating layer is preferably 5 to 15% by mass.

As the positive electrode of the electrode body, for example, a structure having a positive electrode mixture layer containing a positive electrode active material, a solid electrolyte, and, if necessary, a binder, a conductive auxiliary agent, and the like on the current collector can be used.

As the solid electrolyte of the positive electrode, the same sulfide-based solid electrolyte as the solid electrolyte used for the solid electrolyte layer may be used, or different ones such as an oxide-based solid electrolyte and a hydride-based solid electrolyte may be used.

As the positive electrode active material, binder and conductive auxiliary agent, the same ones used for the positive electrode of a lithium ion secondary battery using a non-aqueous electrolyte solution can be used, but a sulfide-based solid electrolyte is used as the solid electrolyte. In this case, it is preferable to use a fluorine-based resin such as polyvinylidene fluoride for the binder in order to prevent the reaction with the solid electrolyte.

The ratio of the positive electrode active material in the positive electrode mixture layer is preferably 50% by mass or more, and more preferably 80% by mass or more. The thickness of the positive electrode mixture layer is preferably 0.02 to 2 mm.

As the positive electrode current collector, a metal foil such as aluminum, a punching metal, a net, an expanded metal, or the like can be used. The thickness of the positive electrode current collector is preferably 10 to 30 μm. As described above, the current collector tab portion of the positive electrode can be provided, for example, by leaving an exposed portion that does not form the positive electrode mixture layer on the positive electrode current collector.

As the negative electrode of the electrode body, for example, a structure having a negative electrode mixture layer containing a negative electrode active material, a solid electrolyte, and, if necessary, a binder, a conductive auxiliary agent, and the like on the current collector can be used.

As the solid electrolyte of the negative electrode, the same sulfide-based solid electrolyte as the solid electrolyte used for the solid electrolyte layer may be used, or different ones such as an oxide-based solid electrolyte and a hydride-based solid electrolyte may be used.

As the negative electrode active material, the binder and the conductive auxiliary agent, the same ones used for the negative electrode of the lithium ion secondary battery using a non-aqueous electrolyte solution can be used, but a sulfide-based solid electrolyte is used as the solid electrolyte. In this case, it is preferable to use a fluorine-based resin such as polyvinylidene fluoride for the binder in order to prevent the reaction with the solid electrolyte.

The ratio of the negative electrode active material in the negative electrode mixture layer is preferably 50% by mass or more, and more preferably 80% by mass or more. The thickness of the negative electrode mixture layer is preferably 0.02 to 2 mm.

As the negative electrode current collector, copper, nickel, stainless steel foil, punching metal, net, expanded metal, or the like can be used. The thickness of the negative electrode current collector is preferably 5 to 30 μm. As described above, the current collector tab portion of the negative electrode can be provided, for example, by leaving an exposed portion that does not form the negative electrode mixture layer in the negative electrode current collector.

The solid electrolyte layer of the electrode body contains a sulfide-based solid electrolyte.

The sulfide-based solid electrolyte contains lithium and sulfur as constituents, and further contains an element selected from phosphorus, germanium, aluminum, boron, silicon, and the like, and has lithium ion conductivity, and is a halogen. It may contain elements such as. Specific examples of such a sulfide-based solid electrolyte include a Li ₂ SP ₂ S ₅ system material, a Li ₂ S—Si S ₂ system material, a Li ₂ S—Ge S ₂ system material, and a Li ₂ S-. Al ₂ S ₃ system material, Li ₂ S-SiS ₂ -Li ₃ PO ₄ system material, Li ₂ SP ₂ S ₅ -GeS ₂ system material, Li ₂ S-Li ₂ O-P ₂ S ₅ -SiS ₂ -based materials, Li ₂ S-GeS ₂ -P ₂ S ₅ -SiS ₂ -based materials, Li ₂ S-SnS ₂ -P ₂ S ₅ -SiS ₂ -based materials, etc. are exemplified, and lithium ion conduction. From the viewpoint of properties, those containing Li, P, and S as constituent elements are preferable.

The solid electrolyte layer may be formed by using a sulfide-based solid electrolyte alone, but it is preferable to use a binder to maintain the shape. As the binder, it is preferable to use a fluororesin such as polytetrafluoroethylene or polyvinylidene fluoride in order to prevent the reaction with the solid electrolyte. The thickness of the solid electrolyte layer is preferably 0.1 to 300 μm.

The electrode body can be formed by laminating a positive electrode and a negative electrode via a solid electrolyte layer, and as shown in FIG. 2, it is configured by laminating a plurality of unit units in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated. You may. The upper limit of the number of unit units constituting the electrode body is not particularly limited, but is usually about three.

In the case of an electrode body in which a plurality of unit units are stacked, the current collecting tabs of all positive electrodes and the current collecting tabs of all negative electrodes may be integrated by welding or the like.

Then, an insulating layer is formed on the side surface of the electrode body, that is, the end face of the positive electrode, the end face of the negative electrode, and the end face of the solid electrolyte layer. The insulating layer on the side surface of the electrode body can be formed, for example, by applying the insulating layer forming composition of the present invention and drying to remove the solvent.

The method for applying the composition for forming an insulating layer is not particularly limited, and a method that can be satisfactorily applied to a portion of the electrode body where the insulating layer needs to be formed may be appropriately selected from various known methods. Further, the method and conditions for drying the solvent are not particularly limited, and a method and conditions for drying the solvent satisfactorily can be appropriately selected from known methods and conditions within a range that does not adversely affect various components of the electrode body. Just do it.

The thickness of the insulating layer is preferably 10 to 50 μm.

The electrochemical element of the present invention has the electrode body of the present invention, and includes a secondary battery, a supercapacitor, and the like.

The electrochemical element includes, for example, an exterior body for accommodating the electrode body, and a positive electrode terminal portion and a negative electrode terminal portion for electrically connecting the electrochemical element and the applicable device.

FIG. 3 shows a cross-sectional view schematically showing an example of the electrochemical device of the present invention. The electrochemical element 1 shown in FIG. 3 is configured such that the electrode body 100 is housed in the metal laminating film exterior body 400. In FIG. 3, each layer of the metal laminated film exterior body and each layer of the electrode body are omitted.

The positive electrode terminal portion 200 of the electrochemical element 1 is connected to the current collecting tab portion of the positive electrode in the metal laminated film exterior body 400 by welding or the like, and the negative electrode terminal portion 300 also collects the negative electrode in the metal laminated film exterior body 400. It is connected to the tab part by welding or the like.

The form of the electrochemical element is not particularly limited, and the form adopted in the electrochemical element having a laminated electrode body, for example, the outer can and the sealing plate are caulked and sealed via a gasket, or the outer can and the sealing plate are sealed. A flat shape (including a coin shape and a button shape) having an exterior body that can be welded and sealed; a laminated shape having an exterior body made of a metal laminate film as shown in FIG. 3; ..

When using an exterior body that has a caulking seal, polypropylene, nylon, etc. can be used as the material of the gasket that is interposed between the exterior can and the sealing plate, and it is heat resistant due to the use of the battery. Is required, fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulphon (PSF), polyallylate (PAR), polyethersulphon (PES). ), Polyphenylene sulfide (PPS), polyetheretherketone (PEEK) and other heat-resistant resins having a melting point of more than 240 ° C. can also be used. Further, when the battery is applied to an application requiring heat resistance, a glass hermetic seal can be used for the sealing.

In manufacturing the electrochemical element of the present invention, if the electrode body of the present invention is housed in the exterior body while connecting the current collecting tab portion of the positive and negative electrodes and the terminal portion of the exterior body, and then sealed. good. Depending on the form of the electrochemical element, a positive and negative electrode current collecting tab portion (in the case where the electrode body has a plurality of positive and negative electrodes, the current collecting tab portions of the same electrode are integrated by welding or the like). , It can be pulled out from the exterior as it is and used as a terminal part of an electrochemical element.

Since the electrochemical element of the present invention has good heat resistance, it is suitably used for applications that can be placed in a high temperature environment, such as various power supply applications for automobiles and industrial use, by taking advantage of these characteristics. In addition to being obtained, it can also be applied to the same applications as ordinary lithium ion secondary batteries and solid-state secondary 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
(Preparation of positive electrode)
Lithium cobaltate, which is a positive electrode active material: 64 parts by mass, and Li ₂ SP ₂ S ₅ system sulfide solid electrolyte: 32 parts by mass are mixed and dispersed in toluene as a dispersion medium, and further. A gas phase growth carbon fiber: 2 parts by mass as a conductive auxiliary agent and PVDF: 2 parts by mass as a binder were added and mixed to prepare a slurry-like composition for forming a positive electrode mixture layer.

The obtained positive electrode mixture layer forming composition is applied to an aluminum foil to be a positive electrode current collector, dried, and pressed to have a positive electrode mixture layer having a thickness of 80 μm on one side of the current collector. Got When forming the positive electrode mixture layer, a part of the current collector was left as an exposed portion in order to form a current collector tab portion.

(Manufacturing of negative electrode)
80 parts by mass of graphite as a negative electrode active material and 20 parts by mass of a Li ₂ SP ₂ S ₅ system sulfide solid electrolyte are mixed and dispersed in toluene as a dispersion medium, and PVDF is further used as a binder. : 2 parts by mass was added and mixed to prepare a slurry-like composition for forming a negative electrode mixture layer.

The obtained composition for forming a negative electrode mixture layer is applied to a copper foil as a negative electrode current collector, dried, and pressed to have a negative electrode mixture layer having a thickness of 60 μm on one side of the current collector. Got When forming the negative electrode mixture layer, a part of the current collector was left as an exposed portion in order to form a current collector tab portion.

(Preparation of composition for forming an insulating layer)
Acrylic resin (glass transition temperature: 50 ° C.): 0.5 g was added to toluene: 16.2 g, and ultrasonic treatment was carried out for 5 minutes to prepare a binder solution.

PMMA particles (pyrolysis temperature: 200 ° C., average particle diameter: 0.5 μm): 1.6 g were added to this binder solution and subjected to ultrasonic treatment again to prepare a slurry for forming an insulating layer. In the obtained slurry for forming an insulating layer, the ratio (mass ratio) of PMMA particles, acrylic resin and toluene is PMMA particles: acrylic resin: toluene = 9: 3: 88, and acrylic to 100 parts by mass of PMMA particles. The ratio of the resin was 33.3 parts by mass.

(Manufacturing of laminated electrode body)
A composition for forming a slurry-like solid electrolyte layer by mixing and dispersing 98 parts by mass of the same sulfide-based solid electrolyte used in the production of the positive electrode and the negative electrode and 2 parts by mass of PVDF as a binder in toluene. Was prepared.

This composition for forming a solid electrolyte layer is applied onto the positive electrode mixture layer of the positive electrode and dried to form a laminate of the positive electrode mixture layer and the solid electrolyte layer, and then the above-mentioned solid electrolyte layer is placed on the solid electrolyte layer. The negative electrode mixture layer of the negative electrode was overlapped, and the whole was further pressed to integrate the whole to form an electrode body sheet. An electrode body (unit unit) was formed by punching this electrode body sheet into the planar shape shown in FIG. As shown in FIG. 2, the obtained three sets of unit units were laminated in the thickness direction so that the positive electrodes and the negative electrodes were in contact with each other to form a laminated electrode body, and the whole was fixed with insulating tape.

Then, the slurry for forming an insulating layer was applied to the side surface of the laminated electrode body in an argon box and dried for 60 minutes to form an insulating layer having a thickness of 50 μm.

(Battery assembly)
For the laminated electrode body on which the insulating layer is formed, all the current collecting tabs of the positive electrode are collectively welded to the aluminum positive electrode terminal (external terminal), and all the current collecting tabs of the negative electrode are also collectively the copper negative electrode terminal. Welded to the part (external terminal). Then, the laminated electrode body after welding was placed on a rectangular metal laminated film so that the positive electrode terminal portion and the negative electrode terminal portion each protruded outward from the opposite sides of the metal laminated film. Then, it is placed on a square metal laminate film from above, and the ends of the upper and lower metal laminate films are heat-welded and sealed to seal the all-solid-state secondary battery having the same cross-sectional structure as that shown in FIG. Electrochemical element) was obtained.

Example 2
All-solid-state secondary battery in the same manner as in Example 1 except that the amounts of PMMA particles, binder and toluene used for preparing the slurry for forming the insulating layer were changed to 1.5 g, 0.8 g and 15.2 g, respectively. Was produced.

In the insulating layer forming slurry used in Example 2, the ratio (mass ratio) of PMMA particles, acrylic resin and toluene is PMMA particles: acrylic resin: toluene = 9: 5: 87, and PMMA particles: 100 mass. The ratio of the acrylic resin to the portion was 55.6 parts by mass.

Comparative Example 1
An all-solid-state secondary battery was produced in the same manner as in Example 1 except that the insulating layer was not formed on the side surface of the laminated electrode body.

Comparative Example 2
An all-solid-state secondary battery in the same manner as in Example 1 except that the amounts of PMMA particles, binders and toluene used for preparing the insulating layer forming slurry were changed to 1.5 g, 0.2 g and 14.9 g, respectively. Was produced.

In the insulating layer forming slurry used in Comparative Example 2, the ratio (mass ratio) of PMMA particles, acrylic resin and toluene is PMMA particles: acrylic resin: toluene = 9: 1: 90, and PMMA particles: 100 mass. The ratio of the acrylic resin to the portion was 11.1 parts by mass.

Comparative Example 3
An all-solid-state secondary battery was prepared in the same manner as in Example 1 except that acetone (δ = 10) was used as a solvent for preparing the binder solution.

Comparative Example 4
When hexane (δ = 7.3) was used as the solvent for preparing the binder solution, a homogeneous binder solution could not be prepared, so that an all-solid-state secondary battery could not be prepared.

(Evaluation of the presence or absence of a short circuit)
The side surfaces of each of the three secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 were pressed and fixed with a load of 4 Nm, and the voltage change of the batteries at that time was measured. Table 1 shows those in which no change in voltage was observed as no short circuit: ○, and those in which the voltage decreased as short circuit: ×.

(Evaluation of electrochemical characteristics)
The secondary batteries of Examples 1 and 2 and Comparative Examples 1 to 3 are charged at a constant voltage with a current value of 0.3 mA until the battery voltage reaches 4.0 V under a room temperature environment, and subsequently, a voltage of 4.0 V is charged. After constant voltage charging was performed until the current value reached 0.15 mA, the discharge capacity at room temperature was measured by constant current discharge until the battery voltage reached 2.0 V at a current value of 0.3 mA.

Table 1 shows the measurement results of each battery when the discharge capacity of Example 1 is represented as 100.

As shown in Table 1, the batteries of Examples 1 and 2 using an electrode body having an insulating layer composed of a heat-resistant resin filler and a binder on the side surface cause a short circuit in the evaluation test for the presence or absence of a short circuit. It was able to be suppressed well. In addition, in the electrochemical property evaluation test, charging and discharging could be performed without any problem.

On the other hand, the battery of Comparative Example 1 using an electrode body having no insulating layer on the side surface and the battery of Comparative Example 2 using an electrode body having an insulating layer formed on the side surface having an excessively small amount of binder have a short circuit. There was a short circuit during the evaluation test. In the electrode body related to the battery of Comparative Example 2, it is considered that the insulating layer having good properties could not be formed because the amount of binder was too small.

Further, in the battery of Comparative Example 3 in which a solvent (acetone) having a solubility parameter larger than 9.5 was used as the solvent for preparing the composition for forming the insulating layer, the battery of Comparative Example 3 was used in the electrochemical property evaluation test. The discharge capacity was lower than that of the battery. In the electrode body related to the battery of Comparative Example 3, it is considered that when the insulating layer forming composition was applied to the side surface of the electrode body, the solid electrolyte in the vicinity of the side surface of the electrode body was deteriorated by the solvent.

1 Electrochemical element 20 Positive electrode 20a Positive electrode main body 20b Positive electrode current collection tab 21 Positive electrode mixture layer 22 Positive electrode current collector 30 Negative electrode 30a Negative electrode main body 30b Negative current collection tab 31 Negative electrode mixture layer 32 Negative electrode collection Electrical body 40 Solid electrolyte layer 50 Insulation layer 100 Electrode body (laminated electrode body)
200 Positive terminal part 300 Negative terminal part 400 Exterior

Claims (10)

A composition for forming an insulating layer used for forming an insulating layer in an electrochemical element having a solid electrolyte layer containing a sulfide-based solid electrolyte.
It contains a filler containing a resin having a melting point or a thermal decomposition temperature of 150 ° C. or higher, a binder, and a solvent having a solubility parameter of 8.8 to 9.5.
A composition for forming an insulating layer, wherein the content of the binder is 15 parts by mass or more with respect to 100 parts by mass of the filler. The composition for forming an insulating layer according to claim 1, wherein the water content of the solvent is 10 ppm or less. The composition for forming an insulating layer according to claim 1 or 2, which contains toluene as the solvent. The composition for forming an insulating layer according to any one of claims 1 to 3, which contains particles of polymethyl methacrylate as the filler. The composition for forming an insulating layer according to any one of claims 1 to 4, wherein the filler has an average particle size of 0.1 to 1 μm. The composition for forming an insulating layer according to any one of claims 1 to 5, which contains an acrylic resin as the binder. An electrode body for an electrochemical element having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.
The solid electrolyte layer contains a sulfide-based solid electrolyte, and the solid electrolyte layer contains a sulfide-based solid electrolyte.
An electrode body for an electrochemical element, characterized in that an insulating layer containing a filler containing a resin having a melting point or a thermal decomposition temperature of 150 ° C. or higher and a binder is formed on a side surface of the electrode body. The positive electrode includes a main body portion having a positive electrode mixture layer containing a positive electrode active material and a solid electrolyte, and a current collecting tab portion protruding from the main body portion.
The electrode body for an electrochemical element according to claim 7, wherein the negative electrode includes a main body portion having a negative electrode mixture layer containing a negative electrode active material and a solid electrolyte, and a current collecting tab portion protruding from the main body portion. .. The electrode body for an electrochemical device according to claim 7 or 8, wherein the insulating layer is formed by using the insulating layer forming composition according to any one of claims 1 to 6. An electrochemical element comprising an electrode body having a positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.
The electrochemical element having the electrode body for an electrochemical element according to any one of claims 7 to 9 as the electrode body.

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