JP2014116154A - Solid-state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long life solid-state battery by reliably improving adhesion at the boundary surfaces of a negative electrode even when a silicon-based active material is used for the negative electrode.SOLUTION: The present invention relates to a solid-state battery including a positive electrode, a negative electrode, and a solid electrolyte provided between the positive electrode and the negative electrode. In the solid-state battery, the negative electrode includes a negative electrode active material, a first binder binding to the solid electrolyte and inactive to the solid electrolyte, and a second binder having more excellent binding properties to a negative electrode collector than the first binder, while the second binder contains a high elastic resin such as polyimide.

Description

  The present invention relates to a solid state battery including a solid electrolyte. The solid state battery of the present invention includes a lithium ion secondary battery and the like.

  For example, as disclosed in Patent Documents 1 to 4 below, a solid battery using a solid electrolyte is known as a lithium ion secondary battery. Such a solid battery includes an electrolyte layer including a solid electrolyte, electrodes (positive electrode and negative electrode) formed on both surfaces of the electrolyte layer, and a current collector bonded to each electrode. In a solid battery, a solid electrolyte is generally used as an electrolyte, and a solid electrolyte is also mixed in each electrode.

  As a method for manufacturing a solid battery, there is a method in which material powders constituting each layer are sequentially inserted into a cylindrical container, compacted, and both ends of the container are closed with current collectors, that is, a compacted manufacturing method. Are known. However, in the manufacturing method by compacting, it is necessary to prepare a container and a pressurizing device according to the size of the electrode area (area where the electrode contacts the electrolyte layer), so it is difficult to increase the electrode area. there were. For this reason, the manufacturing method by compacting cannot cope with the increase in capacity of solid batteries which has been required in recent years.

  Therefore, as another manufacturing method, the material powder, the binder, and the solvent of each layer are mixed to form a coating liquid for each layer, and this coating liquid is sequentially coated on the current collector and dried. A method of forming a laminate and rolling the laminate, that is, a manufacturing method by coating has been proposed. If it is the manufacturing method by coating, since an electrode area can be enlarged only by performing the process of enlarging the coating area of an electrode and an electrolyte layer, an electrode area can be enlarged easily.

  Japanese Patent Application Laid-Open No. 2011-204592 discloses that in a lithium secondary battery using negative electrode active material particles containing silicon and / or a silicon alloy, the binder itself is destroyed during charging and discharging, the negative electrode active material, the negative electrode current collector, and the binder Negative electrode active material particles and binder containing silicon and / or silicon alloy for the purpose of obtaining a lithium secondary battery that suppresses the occurrence of delamination at the interface and has a high energy density and excellent cycle characteristics A lithium secondary battery comprising a negative electrode formed on the surface of a conductive metal foil that is a negative electrode current collector, a positive electrode, and a non-aqueous electrolyte, wherein the binder is 6 Lithium ion characterized by containing a polyimide resin containing a crosslinked structure formed by imidization of a polycarboxylic acid having higher valence or its anhydride and diamine It is described next battery.

JP 2011-076792 A JP 2010-282815 A JP 2010-257878 A JP 2009-054484 A JP 2011-205942 A

  In order to increase the capacity of a lithium ion battery, a technique using a silicon-based active material for the negative electrode has been studied. At present, graphite is mainly used as the negative electrode active material, but its storage capacity is only a fraction of that of the silicon-based active material. On the other hand, although the storage capacity of the silicon-based active material is excellent, there is a problem that expansion and contraction during charging and discharging are large.

  Due to the expansion and contraction of the silicon-based active material, the adhesion at the interface between the negative electrode and the solid electrolyte and the adhesion at the interface between the negative electrode and the negative electrode current collector are affected, and in particular, lithium using a sulfide-based solid electrolyte. In the ion secondary battery, since the overvoltage of the reduction reaction causing lithium metal deposition is low, dendrite is easily generated due to the resistance distribution due to the interfacial resistance in the solid battery, causing an internal short circuit failure. Therefore, since the battery life is significantly reduced, at present, the use of a negative electrode active material in which a silicon-based active material is slightly mixed with graphite is limited.

Although Patent Document 5 discloses a lithium ion secondary battery having an inorganic solid electrolyte such as LiI or Li ₃ N, if a silicon-based material is used as the negative electrode active material, the expansion and contraction of the negative electrode active material during charge / discharge is disclosed. However, no consideration is given to the possibility that peeling may occur at the interface between the solid electrolyte and the negative electrode.

  Accordingly, an object of the present invention is to provide a long-life solid battery by reliably improving the adhesion at the negative electrode interface even when a silicon-based active material is used for the negative electrode.

  To achieve the above object, the present invention comprises a positive electrode, a negative electrode, and a solid electrolyte provided between the positive electrode and the negative electrode, the negative electrode being bound to the negative electrode active material and the solid electrolyte. A first binder that is inert with respect to the solid electrolyte, and a second binder that has a better binding property to the negative electrode current collector than the first binder, The second binder is a solid battery containing a highly elastic resin.

  According to the present invention, a highly elastic resin such as polyimide is used as the binder for the negative electrode, and this resin constrains expansion and contraction during charging and discharging of the negative electrode active material, thereby causing an interface (negative electrode) in the negative electrode. And the solid electrolyte and the interface, and the interface between the negative electrode and the negative electrode current collector) can be stably maintained. Furthermore, since the binder for the negative electrode includes the first binder that binds to the solid electrolyte and is inactive to the solid electrolyte, the adhesion at the interface between the negative electrode and the solid electrolyte is also improved. Be improved. Therefore, according to the present invention, not only the interface between the negative electrode and the negative electrode current collector, but also the adhesion between the negative electrode and the solid electrolyte interface is stable regardless of the expansion and contraction of the negative electrode active material during charging and discharging of the battery. Can be maintained.

In a preferred embodiment of the present invention, the solid electrolyte includes an electrolyte binder having an affinity for the first binder. And as said highly elastic resin, the polyimide of following formula [Chemical Formula 1] is suitable.

  In a further preferred aspect of the present invention, the negative electrode active material is a silicon-based active material. Furthermore, the electrolyte binder includes a first binder. The first binder is a nonpolar resin having no polar functional group. Furthermore, the solid electrolyte is a sulfide-based solid electrolyte. The negative electrode does not contain the solid electrolyte.

  According to the present invention, even when a silicon-based active material is used for the negative electrode, a solid battery having a long life can be provided by reliably improving the adhesion at the interface of the negative electrode.

It is sectional drawing which shows embodiment of the structure of the solid battery which concerns on embodiment of this invention. It is a characteristic view which shows the relationship between the charging capacity and voltage of the solid battery which concerns on an Example and a comparative example.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

<1. Solid battery configuration>
First, based on FIG. 1, the structure of the solid battery 1 which concerns on this embodiment is demonstrated. The solid battery 1 includes a positive electrode current collector 2, an adhesive layer 3, a positive electrode layer 4, an electrolyte layer 5, a negative electrode layer 6, and a negative electrode current collector 7. The adhesive layer 3 and the positive electrode layer 4 constitute the positive electrode 10 of the solid battery 1. Further, the negative electrode layer 6 constitutes the negative electrode 20 of the solid battery 1. Note that the solid battery 1 may not include the adhesive layer 3.

  The positive electrode current collector 2 may be any conductor as long as it is a conductor, and is made of, for example, aluminum, stainless steel, nickel-plated steel, or the like.

  The adhesive layer 3 binds the positive electrode current collector 2 and the positive electrode layer 4. The adhesive layer 3 includes an adhesive layer conductive material, a first binder, and a second binder. The adhesive layer conductive material is, for example, carbon black such as ketjen black, acetylene black, graphite, natural graphite, artificial graphite, etc., but is not particularly limited as long as it is for increasing the conductivity of the adhesive layer 3, They may be used alone or in combination.

  The first binder is, for example, a nonpolar resin having no polar functional group. Therefore, the first binder is inactive to highly reactive solid electrolytes, particularly sulfide-based solid electrolytes. It is known that sulfide-based solid electrolytes are active against polar structures such as acids, alcohols, amines, ethers and the like. The first binder is for binding to the positive electrode layer 4. Here, if the positive electrode layer 4 contains the first binder or a component similar thereto, the first binder in the adhesive layer 3 passes through the interface between the adhesive layer 3 and the positive electrode layer 4. By interdiffusion with the first binder in the positive electrode layer 4, the positive electrode layer 4 is firmly bound. Therefore, the positive electrode layer 4 preferably contains the first binder.

  Examples of the first binder include styrene thermoplastic elastomers such as SBS (styrene butadiene block polymer), SEBS (styrene ethylene butadiene styrene block polymer), styrene-styrene butadiene-styrene block polymer, SBR, and the like. (Styrene butadiene rubber), BR (Butadiene rubber), NR (Natural rubber), IR (Isoprene rubber), EPDM (Ethylene-propylene-diene terpolymer), and partial hydrides or complete hydrides thereof Is exemplified. Other examples include polystyrene, polyolefin, olefinic thermoplastic elastomer, polycycloolefin, and silicone resin.

  The second binder is a binder that has better binding properties to the positive electrode current collector 2 than the first binder. A binder having excellent binding properties to the positive electrode current collector 2 is obtained by, for example, applying a binder film obtained by applying a binder solution to the positive electrode current collector 2 and drying the positive electrode current collector 2. The force required for peeling from the electric body 2 can be determined by measuring with a commercially available peel tester. The second binder is, for example, a polar functional group-containing resin having a polar functional group, and is firmly bound to the positive electrode current collector 2 through a hydrogen bond or the like. However, since the second binder is often highly reactive with the sulfide-based solid electrolyte, it is not included in the positive electrode layer 4.

  Examples of the second binder include NBR (nitrile rubber), CR (chloroprene rubber), partial hydrides thereof, or complete hydrides, copolymers of polyacrylic acid esters, PVDF (polyvinylidene fluoride), and the like. Ride), VDF-HFP (Pinylidene fluoride-hexafluoropropylene copolymer), and their carboxylic acid modified products, CM (chlorinated polyethylene), polymethacrylic acid ester, polyvinyl alcohol, ethylene-vinyl alcohol copolymer Examples include coalescence, polyimide, polyamide, polyamideimide and the like. Moreover, the polymer etc. which copolymerized the monomer which has carboxylic acid, a sulfonic acid, phosphoric acid etc. in said 1st binder are illustrated.

  The content ratio of the adhesive layer conductive material, the first binder, and the second binder is not particularly limited. For example, the adhesive layer conductive material is the total mass of the adhesive layer 3. The first binder is 3 to 30% by mass with respect to the total mass of the adhesive layer 3, and the second binder is 2 to 20 with respect to the total mass of the adhesive layer 3. % By mass.

The positive electrode layer 4 includes a sulfide-based solid electrolyte, a positive electrode active material, a positive electrode layer conductive material, and a positive electrode layer binder. The positive electrode layer conductive material may be the same as the adhesive layer conductive material. Examples of the sulfide-based solid electrolyte include Li ₂ S—P ₂ S ₅ . This sulfide-based solid electrolyte is known to have higher lithium ion conductivity than other inorganic compounds. In addition to Li ₂ S—P ₂ S ₅ , SiS ₂ , GeS ₂ , B ₂ S _3, etc. It may contain sulfide. Further, as the solid electrolyte, an inorganic solid electrolyte to which Li ₃ P0 ₄ , halogen, a halogen compound or the like is appropriately added may be used.

The sulfide-based solid electrolyte is obtained by heating Li ₂ S and P ₂ S ₅ to a melting temperature or higher, melting and mixing them at a predetermined ratio, holding them for a predetermined time, and then rapidly cooling (melting). Quenching method). The obtained processed by mechanical milling method _{Li 2 S-P 2 S 5} . The mixing ratio of Li ₂ S—P ₂ S ₅ is usually 50:50 to 80:20, preferably 60:40 to 75:25 in terms of molar ratio.

In the solid battery 1, the electrolyte is composed of a solid electrolyte. Examples of the solid electrolyte include those containing a lithium ion conductor made of an inorganic compound as the inorganic solid electrolyte in addition to the sulfide-based solid electrolyte. Examples of such lithium ion conductors include Li ₃ N, LIICON, LIPON (Li _{3 + y} PO _4−x N _x ), Thio-LISICON (Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li has _{2 O-Al 2 O 3 -TiO} 2 -P 2 O 5 (LATP). These inorganic compounds can take a crystal, amorphous, glassy, glass ceramic or the like structure.

  The positive electrode active material is not particularly limited as long as it is a material capable of reversibly occluding and releasing lithium ions. For example, lithium cobalt oxide (LCO), lithium nickelate, lithium nickel cobaltate, nickel cobalt aluminum acid Lithium (hereinafter also referred to as “NCA”), nickel cobalt lithium manganate (hereinafter also referred to as “NCM”), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, sulfur , Iron oxide, vanadium oxide and the like. These positive electrode active materials may be used independently and 2 or more types may be used together.

The positive electrode active material is preferably a lithium salt of a transition metal oxide having a layered rock salt type structure, among the examples of the positive electrode active materials listed above. “Layered” as used herein means a thin sheet-like shape, and “rock salt structure” refers to a sodium chloride structure, which is a kind of crystal structure, and includes cations and anions. Each of the face-centered cubic lattices formed by each indicates a structure that is shifted from each other by a half of the edge of the unit lattice. As a lithium salt of a transition metal oxide having such a layered rock salt structure, for example, Li _1-x-yz Ni _x Co _y Al _z O ₂ (NCA) or Li _1-x-yz Ni _x Co _y Mn _z O ₂ (NCM) (0 <x <1, 0 <y <1, 0 <z <1, and x + y + z <1) is represented by a lithium salt of a ternary transition metal oxide. Can be mentioned.

  The positive electrode layer binder is, for example, a nonpolar resin having no polar functional group. Therefore, the positive electrode layer binder is inactive to highly reactive solid electrolytes, particularly sulfide-based solid electrolytes. The positive electrode layer binder preferably includes the first binder described above. Since the electrolyte of the solid battery 1 is a highly reactive sulfide-based solid electrolyte, the positive electrode layer binder is a nonpolar resin.

  Even if the positive electrode layer 4 is directly bound to the positive electrode current collector 2, the positive electrode layer 4 may not be sufficiently bound to the positive electrode current collector 2. Therefore, the adhesive layer 3 containing the first binder and the second binder is interposed between the positive electrode layer 4 and the positive electrode current collector 2. As a result, the first binder in the adhesive layer 3 is firmly bound to the positive electrode layer 4, and the second binder in the adhesive layer 3 is firmly bound to the positive electrode current collector 2. The positive electrode current collector 2 and the positive electrode layer 4 are firmly bound. Here, when the first binder is contained in the positive electrode layer binder, the first binder in the adhesive layer 3 passes through the interface between the adhesive layer 3 and the positive electrode layer 4 and the first binder in the positive electrode layer 4. The positive electrode layer 4 and the positive electrode aggregate 2 are firmly bound by interdiffusion with the binder 1.

  The ratio of the content of the sulfide-based solid electrolyte, the positive electrode active material, the positive electrode layer conductive material, and the positive electrode layer binder is not particularly limited. For example, the sulfide-based solid electrolyte is 20 to 50% by mass with respect to the total mass of the positive electrode layer 4, the positive electrode active material is 45 to 75% by mass with respect to the total mass of the positive electrode layer 4, and the positive electrode layer conductive material is the positive electrode layer. 1 to 10% by mass with respect to the total mass of 4, and the positive electrode layer binder is 0.5 to 4% by mass with respect to the total mass of the positive electrode layer 4.

  The electrolyte layer 5 includes a sulfide-based solid electrolyte and an electrolyte binder. The electrolyte binder is a nonpolar resin having no polar functional group. Accordingly, the electrolyte binder is inactive to highly reactive solid electrolytes, particularly sulfide-based solid electrolytes. The electrolyte binder preferably includes a first binder.

  The first binder in the electrolyte layer 5 interdiffuses with the first binder in the positive electrode layer 4 through the interface between the positive electrode layer 4 and the electrolyte layer 5, so that the positive electrode layer 4 and the electrolyte layer 5 Is firmly bound. The ratio of the content of the sulfide-based solid electrolyte and the electrolyte binder is not particularly limited. For example, the sulfide-based solid electrolyte is 95 to 99 mass% with respect to the total mass of the electrolyte layer 5, and the electrolyte binder is 0.5 to 5 mass% with respect to the total mass of the electrolyte layer 5.

  The negative electrode layer 6 includes a negative electrode active material and a negative electrode binder. The negative electrode binder includes the first binder described above. The first binder of the negative electrode layer 6 interdiffuses with the first binder of the electrolyte layer 5 to firmly adhere the negative electrode layer 6 and the electrolyte layer 5. The binder contains a second binder having a polar functional group in addition to the first binder. As the second binder for the negative electrode, among the materials described above, a high-elasticity resin having a polyimide represented by the following formula [Chemical Formula 2] as a representative example is mainly contained. High elastic resin is resin in the range of 2-15 GPa in the tensile elasticity modulus shown, for example by JISK7162. Examples of such highly elastic resins include wholly aromatic polyamides (aramids) and polyamide imides in addition to polyimide. The second binder firmly adheres the negative electrode layer 6 and the negative electrode current collector 7 to each other. The highly elastic resin constrains the expansion and contraction of the negative electrode active material during charge and discharge, and works to maintain the adhesion between the negative electrode layer 6 and, in particular, the negative electrode layer 6 and the negative electrode current collector 7. .

Formula [Chemical Formula 2] represents a thermoplastic polyimide or a thermosetting polyimide. Polyimide is obtained by heat-treating polyamic acid. R and R ′ are aromatic compounds. An example of the polyimide is shown in the formula [Chemical Formula 3].

  After forming the negative electrode, the second binder of the negative electrode may be made to have the structure of the formula [Chemical Formula 1] by heat treatment or the like. Specifically, after a negative electrode is formed on the negative electrode current collector with polyamic acid, it is chemically changed to a structure represented by the formula [Chemical Formula 1] via a dehydration reaction by heat treatment in an inert atmosphere. When the second binder has the structure of the formula [Chemical Formula 1] by heat treatment, heating for several hours is required at a temperature of 100 to 400 ° C., preferably 6 hours in the range of 200 to 350 ° C. Is within. Within such a range, the dehydration reaction of the polyamic acid can sufficiently proceed, and the second binder can be chemically changed so as to have the structure of the formula [Chemical Formula 1]. Deterioration due to heating of the binder can be suppressed. The average degree of polymerization n of the second binder is preferably 50 to 5000. Within this range, the second binder has sufficient strength against the negative electrode current collector, and at the same time, the negative electrode can be easily formed.

  There are no particular restrictions on the ratio of the content of the first binder and the second binder. The second binder of the negative electrode contains at least a highly elastic resin, but contains other components exemplified as the second binder in the adhesive layer 3 described above. It does not prevent it. The amount of highly elastic resin such as polyimide in the second binder of the negative electrode is preferably 50% by mass or more with respect to the total amount of the second binder.

  The negative electrode active material is a graphite-based material or a silicon-based material. The mixture of both arbitrary ratios may be sufficient. Since the expansion and contraction of the silicon-based active material during charging / discharging is larger than that of the graphite-based active material, the effect of using the second binder of the negative electrode as polyimide is remarkable for the silicon-based active material.

  The graphite-based active material is, for example, a graphite-based material such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, or natural graphite coated with artificial graphite. The silicon-based active material is Si, Si alloy, or silicon oxide. The Si alloy is composed of a Si phase and a phase of an intermetallic compound of Si and one or more other metal elements, and the Si phase reversibly combines with and desorbs Li to occlude and desorb Li. It is a phase that is released and becomes an active material. The phase of the intermetallic compound of Si and other elements (Si-containing intermetallic compound phase) is in close contact with the Si phase, which is the active material, thereby changing the volume (expansion / contraction) of the Si phase during charging / discharging In contrast, the Si phase is restrained, thereby preventing the anode material from being pulverized and extending the cycle life.

  The phase that constrains the volume change of the Si phase uses an intermetallic compound containing Si (intermetallic compound of Si and another element) that does not occlude Li or hardly occludes as the constraining phase. The other element that forms an intermetallic compound with Si is an element that can easily form a stable intermetallic compound with Si. One or two selected from the group 2A elements and transition elements of the long-period periodic table More than seeds. Among these, preferable elements are one or more selected from Mg, Ti, V, Cr, Mn, Co, Cu, Fe and Ni.

  In addition, the finer the metal structure, the greater the contact ratio between the active material phase and the constrained phase, preventing pulverization and extending the cycle life. Rapid solidification is effective as a method for obtaining a fine metal structure. Solidification methods capable of rapid solidification include an atomizing method (including liquid atomizing method and gas atomizing), a roll rapid cooling method (including a single roll rapid cooling method and a twin roll rapid cooling method), and a rotating electrode method. The obtained slab is usually pulverized into a powder and then used as a negative electrode material. The pulverization may be performed by a conventional method such as a jet mill or a ball mill, and the pulverization is preferably performed in a non-oxidizing atmosphere. The particle size of the powder is not particularly limited, but is preferably 1 to 35 μm.

  The negative electrode layer 6 may swell the sulfide-based solid electrolyte from the electrolyte layer 5 when the solid battery 1 is manufactured. That is, the negative electrode layer 6 may contain a sulfide-based solid electrolyte. Therefore, when the second binder described above is included in the negative electrode layer 6, the second binder reacts with the sulfide-based solid electrolyte in the negative electrode layer 6, and thus the sulfide-based solid in the negative electrode layer 6. The electrolyte deteriorates. However, the present inventor has found that if the negative electrode active material is a graphite-based active material, a silicon-based active material, or a mixture of both, the characteristics of the solid battery 1 are improved (see Examples). ). That is, the deterioration of the solid battery 1 is prevented. This means that the negative electrode layer 6 does not require a sulfide-based solid electrolyte. The sulfide-based solid electrolyte is presumed not to swell up to the interface portion between the negative electrode layer 6 and the negative electrode current collector 7.

  Since the sulfide-based solid electrolyte is not required for the negative electrode, the negative electrode layer 6 can contain the second binder of the negative electrode as described above. This second binder is firmly bound to the negative electrode current collector 7 through a hydrogen bond or the like. However, the binding property between the negative electrode layer 6 and the electrolyte layer 5 may not be sufficient with the second binder alone. Therefore, in the present embodiment, the negative electrode layer 6 includes the first binder having affinity for the electrolyte binder in addition to the second binder. Thereby, the 1st binder makes the electrolyte layer 5 and the negative electrode layer 6 adhere | attach firmly. When the first binder is contained in the electrolyte layer 5, the first binder in the negative electrode layer 6 becomes the first binder in the electrolyte layer 5 through the interface between the negative electrode layer 6 and the electrolyte layer 5. Thus, the electrolyte layer 5 and the negative electrode layer 6 can be firmly adhered to each other.

  The ratio of the content of the negative electrode active material, the first binder, and the second binder is not particularly limited. For example, the negative electrode active material is 88 to 98.9% by mass with respect to the total mass of the negative electrode layer 6, and the first binder is 0.1 to 2% by mass with respect to the total mass of the negative electrode layer 6; The binder is 1 to 10% by mass with respect to the total mass of the negative electrode layer 6.

  The negative electrode current collector 7 may be any conductor as long as it is a conductor, and is composed of, for example, nickel, copper, stainless steel, nickel-plated steel, or the like. In addition, you may add a well-known additive etc. to said each layer suitably.

<2. Manufacturing method of solid battery>
Next, an example of a method for manufacturing the solid battery 1 will be described. First, a first binder, a second binder, an adhesive layer conductive material, and a first solvent for dissolving the first binder and the second binder. An adhesive layer coating solution containing is produced. Here, examples of the first solvent include amide solvents such as NMP (N-methylpyrrolidone), DMF (N, N-dimethylformamide), N, N-dimethylacetamide, and alkyls such as butyl acetate and ethyl acetate. Examples include ester solvents, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ether solvents such as tetrahydrofuran and diethyl ether, alcohol solvents such as methanol, ethanol, and isopropyl alcohol. As will be described later, since the adhesive layer 3 does not contain a sulfide solid electrolyte or contains a small amount of a sulfide solid electrolyte swollen from the positive electrode layer 4, a polar solvent is used as the first solvent. Can be used. That is, the present inventor has found a first solvent capable of dissolving the first binder and the second binder, and based on this finding, has arrived at the production method of the present embodiment. .

  Next, the adhesive layer coating liquid is applied onto the positive electrode current collector 2 and dried to produce the adhesive layer 3. In addition, an adhesive layer coating solution may be applied to a substrate such as a desktop screen printing machine and dried to form an adhesive film, and the adhesive film may be pressure-bonded to the positive electrode current collector 2.

  Next, a sulfide-based solid electrolyte, a positive electrode active material, a positive electrode layer conductive material, a positive electrode layer binder, a second solvent for dissolving the positive electrode layer binder and the first binder, A positive electrode layer coating solution containing is produced. The second solvent dissolves the positive electrode layer binder (first binder) but does not dissolve the second binder. The second solvent is specifically a nonpolar solvent, and examples thereof include aromatic hydrocarbons such as xylene, toluene, and ethylbenzene, and aliphatic hydrocarbons such as pentane, hexane, and heptane. Next, the positive electrode layer coating liquid is applied onto the adhesive layer 3 and dried to produce the positive electrode layer 4. Thereby, since the 1st binder in the contact bonding layer 3 melt | dissolves in the positive electrode layer 4 by melt | dissolving in a 2nd solvent, the binding | bonding of the contact bonding layer 3 and the positive electrode layer 4 becomes stronger. Thus, in this embodiment, since the positive electrode 10 is produced | generated by coating, the large area positive electrode 10 can be manufactured easily. That is, in this embodiment, the large-capacity solid battery 1 can be easily manufactured.

  In addition, since the second solvent does not dissolve the second binder, when the positive electrode layer coating solution is applied onto the adhesive layer 3, the second binder in the adhesive layer 3 becomes the positive electrode layer 4. Swelling inside is prevented. This prevents the sulfide solid electrolyte in the positive electrode layer 4 from being deteriorated by the second binder. Through the above steps, a positive electrode structure including the positive electrode current collector 2, the adhesive layer 3, and the positive electrode layer 4 is generated.

  On the other hand, a negative electrode layer coating liquid containing a first binder, a second binder, a negative electrode active material, and a first solvent is generated. Since the negative electrode layer 6 does not require a sulfide-based solid electrolyte, a polar solvent can be used as the first solvent. Next, the negative electrode layer coating liquid is applied onto the negative electrode current collector 7 and dried to produce the negative electrode layer 6. Thereby, a negative electrode structure is produced.

  Next, an electrolyte layer coating solution containing a sulfide-based solid electrolyte, an electrolyte binder, and a second solvent is generated. The second solvent dissolves the electrolyte binder (first binder), but does not dissolve the second binder. Next, the electrolyte layer coating liquid is applied onto the negative electrode layer 6 and dried to produce the electrolyte layer 5. Thereby, since the 1st binder in the negative electrode layer 6 is dissolved in the electrolyte layer 5 by melt | dissolving in a 2nd solvent, the binding with the electrolyte layer 5 and the negative electrode layer 6 becomes firmer. Further, since the second solvent does not dissolve the second binder, when the electrolyte layer coating solution is applied onto the negative electrode layer 6, the second binder in the negative electrode layer 6 becomes the electrolyte layer 5. Swelling inside is prevented. This prevents the sulfide solid electrolyte in the electrolyte layer 5 from being deteriorated by the second binder.

  Subsequently, the solid battery 1 is produced | generated by crimping | bonding the positive electrode structure and the sheet | seat which consists of the electrolyte layer 5 and a negative electrode structure. Thus, in this embodiment, since each layer of the solid battery 1 is produced | generated by coating, the area of each layer can be enlarged easily. That is, in this embodiment, the large-capacity solid battery 1 can be easily manufactured.

Next, examples of the present embodiment will be described. In addition, all the operations in the following Examples and Comparative Examples were performed in a dry room having a dew point temperature of −55 ° C. or lower.
[Example 1]
[Generation of adhesive layer]
Adhesive layer conductive material graphite (Timcal KS-4, the same applies hereinafter) and acetylene black (electrochemical industry, the same applies hereinafter), and styrene thermoplastic elastomer as the first binder (hereinafter referred to as the binder) A) (Asahi Kasei S.E.E 1611, the same shall apply hereinafter) and acid-modified PVDF (hereinafter referred to as Binder B) (Kureha KF 9200, same shall apply hereinafter) as the second binder 60: 10: 15: 15 Weighed at a mass% ratio. Then, these materials and an appropriate amount of NMP were put into a rotation and revolution mixer, and stirred at 3000 rpm for 5 minutes to produce an adhesive layer coating solution.

  Next, an aluminum foil current collector having a thickness of 20 μm is placed as a positive electrode current collector 2 on a desktop screen printing machine (manufactured by Neuron Ring Seimitsu Kogyo Co., Ltd., the same shall apply hereinafter), and an adhesive layer coating solution is used using a 400 mesh screen. Was coated on an aluminum foil current collector. Thereafter, the positive electrode current collector 2 coated with the adhesive layer coating solution was vacuum-dried at 80 ° C. for 12 hours. Thereby, the adhesive layer 3 was formed on the positive electrode current collector 2. The thickness of the adhesive layer 3 after drying was 7 μm.

[Creation of positive electrode layer]
LiNiCoAlO ₂ ternary powder as a positive electrode active material, Li ₂ S—P ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte, and positive electrode layer conductive material (conductive aid) ) As a vapor-grown carbon fiber powder in a mass ratio of 60: 35: 5 and mixed using a rotating and rotating mixer.

  Next, a xylene solution in which the binder A as the positive electrode layer binder is dissolved is added to the mixed powder so that the binder A is 1.0% by mass with respect to the total mass of the mixed powder. A primary mixed solution was prepared. Furthermore, a secondary mixed solution was generated by adding an appropriate amount of dehydrated xylene for viscosity adjustment to this mixed solution. Furthermore, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is changed into a secondary mixed solution so that the space, the mixed powder, and the zirconia ball each occupy 1/3 of the total volume of the kneading container. I put it in. The tertiary mixed liquid produced | generated by this was thrown into the rotation-revolution mixer, and the positive electrode layer coating liquid was produced | generated by stirring at 3000 rpm for 3 minutes.

  Subsequently, the sheet | seat which consists of the positive electrode electrical power collector 2 and the contact bonding layer 3 was mounted in the desk screen printer, and the positive electrode layer coating liquid was applied on the sheet | seat using a 150 micrometer metal mask. Then, after drying the sheet | seat with which the positive electrode layer coating liquid was coated with a 40 degreeC hotplate for 10 minutes, it was vacuum-dried at 40 degreeC for 12 hours. Thereby, the positive electrode layer 4 was formed on the adhesive layer 3. The total thickness of the positive electrode current collector 2, the adhesive layer 3, and the positive electrode layer 4 after drying was around 165 μm.

  Subsequently, the sheet | seat which consists of the positive electrode electrical power collector 2, the contact bonding layer 3, and the positive electrode layer 4 was rolled using the roll press machine with a roll gap of 10 micrometers, and the positive electrode structure was produced | generated. The thickness of the positive electrode structure was around 120 μm.

[Formation of negative electrode layer]
Graphite powder as a negative electrode active material (dried at 80 ° C. for 24 hours), binder A as a first binder, and binder C (polyamic acid type as a second binder) Polyimide resin Hitachi Chemical HCI1000S, elastic modulus 2.5 GPa) was weighed at a mass% ratio of 94.5: 0.5: 5.0. Then, these materials and an appropriate amount of NMP were put into a rotation and revolution mixer, stirred for 3 minutes at 3000 rpm, and then subjected to defoaming treatment for 1 minute to produce a negative electrode layer coating solution.

  Next, a 16 μm-thick copper foil current collector was prepared as the negative electrode current collector 7, and the negative electrode layer coating solution was applied onto the copper foil current collector using a blade. The thickness (gap) of the negative electrode layer coating solution on the copper foil current collector was around 150 μm.

  The sheet coated with the negative electrode layer coating solution was stored in a dryer heated to 80 ° C. and dried for 20 minutes. Then, the sheet | seat which consists of the negative electrode electrical power collector 7 and the negative electrode layer 6 was rolled using the roll press machine with a roll gap of 10 micrometers, and the negative electrode structure was produced | generated. The thickness of the negative electrode structure was about 100 μm. Further, the rolled sheet was vacuum heated at 300 ° C. for 2 hours. Thereby, the negative electrode layer 6 in which the binder C was imidized was generated.

[Creation of electrolyte layer]
The _{Li 2 S-P 2 S 5} (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte, binder A xylene solution of the binder A (electrolyte binder) amorphous The primary liquid mixture was adjusted by adding 1 mass% with respect to the mass of the powder. Furthermore, a secondary mixed solution was generated by adding an appropriate amount of dehydrated xylene for viscosity adjustment to the primary mixed solution. Furthermore, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is changed into a secondary mixed solution so that the space, the mixed powder, and the zirconia ball each occupy 1/3 of the total volume of the kneading container. I put it in. The tertiary mixture produced in this way was put into a rotation and revolution mixer and stirred at 3000 rpm for 3 minutes to produce an electrolyte layer coating solution.

  Next, the negative electrode structure was placed on a desktop screen printer, and an electrolyte layer coating solution was applied onto the negative electrode structure using a 200 μm metal mask. Thereafter, the sheet coated with the electrolyte layer coating solution was dried on a hot plate at 40 ° C. for 10 minutes and then vacuum dried at 40 ° C. for 12 hours. Thereby, the electrolyte layer 5 was formed on the negative electrode structure. The thickness of the electrolyte layer 5 after drying was around 130 μm.

[Production of solid battery]
A sheet consisting of the negative electrode structure and the electrolyte layer 5 and the positive electrode structure are each punched out with a Thomson blade, and the dry electrolyte method using a roll press machine with a roll gap of 50 μm is applied to the electrolyte layer 5 and the positive electrode layer 4 of the positive electrode structure The single cell (single cell) of the solid battery 1 was produced by bonding together.

[Example 2]
[Generation of positive electrode structure]
A positive electrode structure was produced by the same process as in Example 1.

[Formation of negative electrode layer]
Si alloy powder as negative electrode active material (dried in vacuum at 80 ° C. for 24 hours), binder A as first binder, and binder C (polyamic acid as second binder) Type polyimide resin Hitachi Chemical HCI1000S) was weighed at a mass% ratio of 94.5: 0.5: 5.0. Then, these materials and an appropriate amount of NMP were put into a rotation and revolution mixer, stirred for 3 minutes at 3000 rpm, and then subjected to defoaming treatment for 1 minute to produce a negative electrode layer coating solution.

  Next, a 16 μm-thick copper foil current collector was prepared as the negative electrode current collector 7, and the negative electrode layer coating solution was applied onto the copper foil current collector using a blade. The thickness (gap) of the negative electrode layer coating solution on the copper foil current collector was around 100 μm.

  The sheet coated with the negative electrode layer coating solution was stored in a dryer heated to 80 ° C. and dried for 20 minutes. Then, the sheet | seat which consists of the negative electrode electrical power collector 7 and the negative electrode layer 6 was rolled using the roll press machine with a roll gap of 10 micrometers, and the negative electrode structure was produced | generated. The thickness of the negative electrode structure was about 70 μm. Further, the rolled sheet was subjected to vacuum heating at 350 ° C. for 2 hours. Thereby, the negative electrode layer 6 in which the binder C was imidized was generated.

[Creation of electrolyte layer]
An electrolyte layer was produced by the same process as in Example 1.

[Production of solid battery]
A single cell of a solid battery was produced by the same process as in Example 1.

[Comparative Example 1]
[Generation of positive electrode structure]
A positive electrode structure was produced by the same process as in Example 1.
[Formation of negative electrode layer]
A negative electrode structure having a thickness of about 100 μm was obtained in the same manner as in Example 1 except that the second binder was binder B and the vacuum heating after rolling of the negative electrode structure was 80 ° C. for 24 hours.
[Creation of electrolyte layer]
An electrolyte layer was produced by the same process as in Example 1.
[Production of solid battery]
A single cell of a solid battery was produced by the same process as in Example 1.

[Comparative Example 2]
[Generation of positive electrode structure]
A positive electrode structure was produced by the same process as in Example 1.

[Formation of negative electrode layer]
A negative electrode structure was produced in the same manner as in Example 2, except that only the binder C as the second binder was changed to 5.5% by mass.
[Creation of electrolyte layer]
An electrolyte layer was produced by the same process as in Example 1.
[Production of solid battery]
A single cell of a solid battery was produced by the same process as in Example 1.

[Internal short circuit during charging]
A single cell manufactured as described above was charged at a constant current density of 0.05 mA / cm ² by a charge / discharge evaluation apparatus TOSCAT-3100 manufactured by Toyo System, and subsequently discharged, and the discharge capacity (mAh) was measured. (Charge upper limit voltage 4.0V, discharge lower limit voltage 2.5V). Based on the measured discharge capacity, current densities corresponding to 0.025C, 0.05C, 0.075C, 0.1C, and 0.15C were calculated. 1C means 1 hour rate current (mA). Each single cell was charged with the current density thus calculated, and the presence or absence of an internal short circuit was determined from the charging profile at that time. An example is shown in FIG. In a battery that has been normally charged, the single cell voltage monotonously increases as the battery is charged. On the other hand, a single cell in which a minute internal short circuit has occurred does not stably increase the single cell voltage during charging. The results of evaluating the internal short circuit of each single cell in this way are shown in Table 1.

[Cycle life test]
A constant current charge / discharge cycle test of 0.05C was performed at room temperature, and the capacity retention rate with respect to the initial discharge capacity was evaluated. The results of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1. Since Comparative Example 1 does not include polyimide (PI) as the second binder in the negative electrode layer, a smile internal short circuit occurs due to lithium dendrite precipitation as compared with Example 1 when the charging current value increases. The voltage becomes unstable and the battery becomes defective.

  Since Examples 1 and 2 both contain the first binder and polyimide (PI: Binder C), the charging characteristics and cycle life characteristics were also good. On the other hand, Comparative Example 2 contains polyimide in the negative electrode layer but does not contain the first binder. Therefore, as compared with Example 2, when the charging current value is increased, the minute internal accompanying lithium dendrite precipitation A short circuit occurred, the voltage became unstable, and a tendency to deteriorate as a battery was observed. Moreover, the comparative example 2 which does not contain the 1st binder had the cycle life characteristic degraded compared with Example 2 containing the 1st binder. Since Comparative Example 1 did not contain polyimide, when the charging current value was increased, an internal short circuit occurred due to lithium dendrite precipitation, and the cycle life characteristics were greatly deteriorated.

  As described above, the negative electrode layer 6 of this embodiment, that is, the negative electrode 20 is bound to the electrolyte layer 5 containing a sulfide-based solid electrolyte, and is inert to the national body electrolyte, Since the second binder, which is superior in binding to the negative electrode current collector than the first binder, includes a negative electrode active material, and the second binder is made of a highly elastic resin such as polyimide. In addition, even when charging / discharging of the solid battery is repeated, the adhesion at the interface between the negative electrode and the solid electrolyte and at the interface between the negative electrode and the negative electrode current collector can be improved.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes and modifications within the scope of the technical idea described in the claims. Of course, these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Solid battery 2 Positive electrode collector 3 Adhesive layer 4 Positive electrode layer 5 Electrolyte layer 6 Negative electrode layer 7 Negative electrode collector

Claims (8)

A positive electrode;
A negative electrode,
A solid electrolyte layer comprising a solid electrolyte provided between the positive electrode and the negative electrode;
With
The negative electrode is
A negative electrode active material;
A first binder that binds to the solid electrolyte and is inert to the solid electrolyte;
A second binder whose binding property to the negative electrode current collector is superior to that of the first binder;
Have
The second binder contains a highly elastic resin;
Solid battery.   The solid battery according to claim 1, wherein the solid electrolyte layer has an electrolyte binder containing the first binder. The solid battery according to claim 1, wherein the highly elastic resin includes a polyimide represented by the following formula [Chemical Formula 1].
  4. The solid state battery according to claim 1, wherein the negative electrode active material is made of a silicon-based active material.   The solid battery according to claim 2, wherein the electrolyte binder includes a first binder.   The solid battery according to any one of claims 1 to 5, wherein the first binder is made of a nonpolar resin having no polar functional group.   The solid battery according to claim 1, wherein the solid electrolyte is made of a sulfide-based material.   The solid battery according to claim 1, wherein the negative electrode does not include the solid electrolyte.