JP2014112485A - Solid state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid state battery preventing the generation of dendrite by causing no deterioration in adhesion between an electrode layer and a solid electrolyte layer through suppression or alleviation of an influence due to expansion and contraction of an electrode active material accompanying charging/discharging, thereby achieving excellent cycle characteristics.SOLUTION: The present invention relates to a solid state battery including a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte. In the solid state battery, a hydrocarbon-based polymer is contained in one of the positive electrode, the negative electrode and the electrolyte layer, and the hydrocarbon-based polymer has a crosslinked structure.

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.

  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. A sulfide-based solid electrolyte having a high ionic conductivity is known as a fixed electrolyte.

  As this type of lithium ion battery, for example, a battery described in JP 2010-106252 A exists. Japanese Patent Application Laid-Open No. 2010-106252 discloses a sulfide-based solid electrolyte sheet obtained by adding sulfur to a polymer obtained by adding polyethylene glycol to a diene polymer terminal, and thereby improving the mechanical strength and durability of the solid electrolyte. It is disclosed to improve.

  In addition, JP 2010-186682 A discloses that by combining the sulfur component in the sulfide-based solid electrolyte material and the double bond of the binder polymer, without reducing flexibility and workability, A solid electrolyte layer having an improved lithium ion conductivity by reducing the amount of binder polymer is disclosed.

JP 2010-106252 A JP 2010-186682 A

  In the solid battery described above, there is a problem in that the adhesion between the electrode layer and the solid electrolyte layer is reduced due to expansion and contraction of the electrode active material accompanying charge / discharge, and the interface resistance is increased. Since the sulfide-based solid electrolyte has a low overvoltage of the oxidation-reduction reaction in the dissolution and precipitation reaction of lithium metal, when it is applied to a lithium ion secondary battery, it is charged due to a change in the relative potential of the positive and negative electrodes accompanying an increase in the positive electrode interface resistance. As the discharge is repeated, lithium metal on the surface of the negative electrode layer is likely to precipitate, grows in a dendrite shape through cracks in the solid electrolyte layer, reaches the positive electrode, and causes an internal short circuit failure. The above-mentioned publications do not consider this issue.

  Therefore, the present invention suppresses or alleviates the influence caused by the expansion and contraction of the electrode active material that accompanies charge / discharge, so that the adhesion between the electrode layer and the solid electrolyte layer does not decrease, and dendrites Therefore, an object of the present invention is to provide a solid battery excellent in cycle characteristics and a method for manufacturing the same.

  In order to achieve the above object, the present invention comprises a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte, and includes any one of the positive electrode, the negative electrode, and the electrolyte layer. In addition, a hydrocarbon polymer is contained, and the hydrocarbon polymer is a solid state battery having a crosslinked structure.

  In a preferred embodiment of the present invention, the hydrocarbon polymer has alkane or alkene as the main chain, and is crosslinked at a part of the main chains. Moreover, after forming a film for forming the positive electrode, the negative electrode, or the electrolyte, the hydrocarbon compound is cross-linked to be insoluble or hardly soluble in a solvent. The activation for crosslinking of the hydrocarbon polymer is performed by electron beam polymerization or thermal polymerization.

  The activation treatment is performed in a state where the positive electrode, the negative electrode, and the electrolyte layer are overlapped. Furthermore, the positive electrode and the negative electrode are each connected to a current collector by the crosslinked hydrocarbon polymer.

  The hydrocarbon polymer is contained as a binder in at least one of the positive electrode, the negative electrode, and the electrolyte layer. Furthermore, the hydrocarbon polymer is contained in the electrolyte layer. In addition, the hydrocarbon contained in the electrolyte layer penetrates and crosslinks the positive electrode and / or the negative electrode.

  Another invention for achieving the above object is a method for producing a solid battery comprising a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte. A solid battery in which a hydrocarbon polymer is contained in either the negative electrode or the electrolyte layer, and the hydrocarbon polymer is crosslinked to form a laminated structure of the positive electrode, the negative electrode, and the electrolyte It is the manufacturing method of this.

  According to the present invention, an increase in battery internal resistance is suppressed by suppressing or mitigating the influence of expansion and contraction of the electrode active material that accompanies charging and discharging, and adhesion between the electrode layer and the solid electrolyte layer is suppressed. It is possible to provide a solid battery excellent in cycle characteristics by preventing the occurrence of dendrite by preventing the deterioration.

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.

<Configuration of solid state battery>
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 is preferably provided in order to bind 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 or acetylene black, graphite, natural graphite, artificial graphite or the like, but is not particularly limited as long as it is for increasing the conductivity of the adhesive layer 3. , 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 PO 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 85:15, preferably 65:35 to 80:20, as a 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.

  The mixture of the positive electrode layer contains a hydrocarbon polymer as an adhesive component. This hydrocarbon polymer is cross-linked by activation treatment of the hydrocarbon polymer at the time of manufacturing the battery to increase rigidity or elasticity in the positive electrode layer, and is also cross-linked with the hydrocarbon polymer of the electrolyte layer. By doing so, the adhesion degree of a layer interface is improved.

  The characteristics of the hydrocarbon polymer are substantially the same as those of the first binder described above, are nonpolar, and are inert to the sulfide solid electrolyte. The hydrocarbon polymer is the same component as the first binder and may also serve as the first binder, or may be added to the positive electrode mixture separately from the first binder. .

  Hydrocarbon polymers can be crosslinked without the need for a cross-linking agent by activation treatment, and therefore have a structure suitable for unsaturated bonds or radicalization in the molecule. Is preferred. Hydrocarbon polymers include alkanes and alkenes. In the hydrocarbon polymer, a third component may be added or condensed to a skeleton composed of carbon and hydrogen.

  The activation conditions or the activation treatment for crosslinking the hydrocarbon polymer includes electron beam polymerization treatment such as radiation, thermal polymerization treatment, and the like. In the hydrocarbon polymer, the main chains are partially crosslinked by the activation treatment, and hardly or insoluble in the nonpolar solvent, thereby achieving the function as an adhesive.

  Examples of the hydrocarbon polymer include SBS (styrene butadiene block polymer), SEBS (styrene ethylene butadiene styrene block polymer), and styrene-styrene butadiene-styrene block polymer, which are also the first binder. There are styrenic thermoplastic elastomers, SBR (styrene butadiene rubber), BR (butadiene rubber), EPDM (ethylene-propylene-diene terpolymer). When the inventor examined, EPDM was preferred. In the case where the hydrocarbon polymer also serves as the first binder, the content allowed for the first binder may be sufficient. When added to the positive electrode mixture separately from the first binder, the content is less than the content permitted for the second binder, and the second binder and The total amount may be the content allowed for the second binder.

  Since the hydrocarbon polymer is cross-linked and can be bonded to the positive electrode current collector as an adhesive, the above-described positive electrode adhesive layer can be omitted.

  Since the hydrocarbon polymer has a crosslinked structure, elasticity that can resist expansion and contraction of the positive electrode active material during charge and discharge is imparted to the positive electrode, and the volume change of the positive electrode active material is suppressed or mitigated. There is also an effect of maintaining a stable interface state between the positive electrode layer and the solid electrolyte layer and preventing a decrease in adhesion between them. The activation process for cross-linking may be performed after the battery cell is configured, or may be performed at the stage of forming the positive electrode.

  In order to sufficiently bind the positive electrode layer 4 to the positive electrode current collector 2, as described above, the adhesive layer 3 including the first binder and the second binder is bonded to the positive electrode layer 4 and the positive electrode current collector 2. You may make it interpose between. As a result, the first binder (hydrocarbon polymer) in the adhesive layer 3 is firmly bound to the positive electrode layer 4, and the second binder in the adhesive layer 3 is also connected to the positive electrode current collector 2. Since it is firmly bound, 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 current collector 2 are firmly bonded by interdiffusion with the first binder.

  In addition, the ratio of the contents 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 mixture of the electrolyte layer contains the hydrocarbon polymer. As described above, the hydrocarbon polymer may also serve as the electrolyte binder (first binder), or may be added to the solid electrolyte separately.

  The first binder (hydrocarbon polymer) in the electrolyte layer 5 is mixed with the first binder (hydrocarbon polymer) in the positive electrode layer 4 through the interface between the positive electrode layer 4 and the electrolyte layer 5. By positive diffusion, the positive electrode layer 4 and the electrolyte layer 5 are 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, a first binder (hydrocarbon polymer), and a second binder. Examples of the negative electrode active material include graphite-based active materials such as artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, and natural graphite coated with artificial graphite.

  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 is included in the negative electrode layer 6, the second binder reacts with the sulfide solid electrolyte in the negative electrode layer 6, so that the sulfide solid electrolyte in the negative electrode layer 6 deteriorates. To do. However, if the negative electrode active material is a graphite active material, deterioration of the solid battery 1 is prevented. This means that a sulfide-based solid electrolyte is not essential for the negative electrode layer 6 if the negative electrode active material is a graphite active material. The sulfide-based solid electrolyte does not swell up to the interface portion between the negative electrode layer 6 and the negative electrode current collector 7.

  Therefore, the second binder can be included in the negative electrode layer 6. The second binder is firmly bound to the negative electrode current collector 7 through a hydrogen bond. 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 (hydrocarbon polymer) in addition to the second binder. Thereby, the first binder is firmly bound to the electrolyte layer 5. The first binder in the negative electrode layer 6 is interdiffused with the first binder in the electrolyte layer 5 through the interface between the negative electrode layer 6 and the electrolyte layer 5, thereby binding the electrolyte layer 5 more firmly. Can be worn. Although the first binder has been described as being a hydrocarbon polymer, the hydrocarbon polymer may be added to the negative electrode mixture as a separate material from the first binder. .

  In the same way that the hydrocarbon polymer in the positive electrode layer is cross-linked, the hydrocarbon polymer in the negative electrode layer is also cross-linked so that the negative electrode has elasticity that can resist expansion and contraction of the negative electrode active material during charge and discharge. In order to suppress or alleviate the volume change of the negative electrode active material by being applied, there is an effect of maintaining a stable interface state between the negative electrode layer and the solid electrolyte layer and preventing a decrease in adhesion between them. The activation process for cross-linking may be performed after the battery cell is configured, or may be performed at the time of forming the negative electrode.

  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 95 to 99% by mass with respect to the total mass of the negative electrode layer 6, and the first binder is 0.5 to 5% by mass with respect to the total mass of the negative electrode layer 6, and the second binder. The agent is 0.5 to 5% 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.

  The above-mentioned second binder is not necessarily essential for the negative electrode. The hydrocarbon polymer in the negative electrode can be bound to the negative electrode current collector as an adhesive by an activation treatment. As described above, this function is the same as the adhesion of the positive electrode to the positive electrode current collector.

  In the above description, it is assumed that the hydrocarbon polymer is contained in the positive electrode, the negative electrode, and the electrolyte layer. However, the effect of the present invention can be achieved if it is contained in one or more of them. The hydrocarbon polymer can be cross-linked in each layer, thereby strengthening the elasticity and rigidity of each layer and resisting the stress of expansion and contraction of the electrode active material. Further, when the positive electrode-electrolyte layer and the electrolyte-positive electrode are bonded, the bonding strength can be maintained or improved by crosslinking of the hydrocarbon polymer. When joining two layers, since the hydrocarbon polymer contained in the solvent can move from one layer to the other, at least one of the two layers contains the hydrocarbon polymer. Just do it. From this point of view, the effect of the present invention can be achieved if at least the solid polymer contains a hydrocarbon polymer.

<2. Manufacturing method of solid battery>
Next, a method for manufacturing a solid battery will be described before the description of the examples. In the first embodiment, after printing each of the positive electrode and the electrolyte layer, the electrolyte layer is transferred to the positive electrode layer, dry lamination is performed by a pressure roll, and the positive electrode / electrolyte layer is crosslinked by irradiation with an electron beam from the electrolyte layer surface; The negative electrode layer is further bound by a roll press to produce a battery. Crosslinking with respect to the hydrocarbon compound is performed between the positive electrode and the electrolyte layer.

  The solvent for the first binder (hydrocarbon compound) is not particularly limited as long as it can dissolve the hydrocarbon compound, but it is an aromatic or hydrocarbon nonpolar or nonpolar solvent. For example, aromatic hydrocarbons such as xylene, toluene, and ethylbenzene, and aliphatic hydrocarbons such as pentane, hexane, and heptane are preferable. In addition, amide solvents such as NMP (N-methylpyrrolidone), DMF (N, N-dimethylformamide), N, N-dimethylacetamide, alkyl ester solvents such as butyl acetate and ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone And the like, ketone solvents such as tetrahydrofuran and diethyl ether, alcohol solvents such as methanol, ethanol and isopropyl alcohol.

  The second correspondence is that a positive electrode is produced by printing, and the positive electrode is cured by irradiating an electron beam to crosslink the hydrocarbon polymer of the positive electrode. An electrolyte layer is printed on the positive electrode, and further irradiated with an electron beam to similarly cure the electrolyte layer. Thereafter, the negative electrode layer is further bound by a roll press to produce a battery. The chemical crosslinking between the positive electrode and the electrolyte is realized by further electron beam irradiation after penetration of the hydrocarbon-based compound contained in the electrolyte layer printed on the positive electrode.

  The third correspondence is that after printing the positive electrode, the negative electrode, and the electrolyte layer, the electrolyte layer is transferred to the positive electrode layer, then the negative electrode is superimposed on the electrolyte layer, and the positive electrode / electrolyte layer / negative electrode is dry-laminated by a pressure roll. Then, an electron beam is irradiated from the negative electrode surface to produce a battery. The positive electrode, the negative electrode, and the electrolyte layer contain a hydrocarbon polymer. The crosslinking of the hydrocarbon polymer is achieved between the positive electrode, the electrolyte layer, and the negative electrode.

  In this manufacturing mode, since the positive electrode is generated by coating, a large-area positive electrode can be easily manufactured. That is, the large-capacity solid battery 1 can be easily manufactured.

<Example>
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]
[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 vapor-grown carbon as a conductive aid The fiber powder was weighed in a mass% ratio of 60: 35: 5: and mixed using a rotation and revolution mixer.

  Next, to this mixed powder, a xylene solution in which a binder (herein, ethylene propylene diene rubber, hereinafter referred to as EPDM) is dissolved is added so that EPDM becomes 2.0 mass% with respect to the total mass of the mixed powder. A primary mixed solution was prepared. Furthermore, a secondary mixed liquid was produced by adding an appropriate amount of dehydrated xylene for viscosity adjustment. 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.

  Next, the positive electrode current collector 2 was placed on a desktop screen printing machine, and the positive electrode layer coating solution was applied onto the sheet using a 100 μm 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. The total thickness of the positive electrode current collector 2 and the positive electrode layer 3 after drying was around 125 μm.

  Subsequently, the sheet | seat which consists of the positive electrode electrical power collector 2 and the positive electrode layer 3 was pressed 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 about 80 μm.

[Formation of negative electrode layer]
Graphite powder as a negative electrode active material (vacuum dried at 80 ° C. for 24 hours), Li ₂ S—P ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte, and conductive assistant The vapor-grown carbon fiber powder as an agent was weighed at a mass% ratio of 60: 35: 5: and mixed using a rotation and revolution mixer. Subsequently, the xylene solution in which EPDM was dissolved was added to the mixed powder so that the EPDM was 2.0% by mass with respect to the total mass of the mixed powder, thereby adjusting the primary mixed solution. Furthermore, a secondary mixed liquid was produced by adding an appropriate amount of dehydrated xylene for viscosity adjustment. 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 negative electrode layer coating liquid was produced | generated by stirring at 3000 rpm for 3 minutes.

  Next, the negative electrode current collector 6 was placed on a desktop screen printing machine, and the negative electrode layer coating solution was applied onto the sheet using a 100 μm metal mask. Then, after drying the sheet | seat with which the negative 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 negative electrode layer 5 was formed. The total thickness of the negative electrode current collector 6 and the negative electrode layer 5 after drying was around 125 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 current collection member 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 80 μm. Further, the rolled sheet was vacuum-dried at 40 ° C. for 12 hours to produce the negative electrode layer 6.

[Creation of electrolyte layer]
Li ₂ S—P ₂ S ₅ (80:20 mol%) as a sulfide-based solid electrolyte was added to a xylene solution of binder EPDM in an amorphous powder, and Li ₂ S—P ₂ S ₅ (80:20 mol%). ) The primary mixed solution was prepared by adding 2% by mass with respect to the mass of the amorphous 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 printing machine, and the electrolyte layer coating solution was applied to the aluminum foil using a 150 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. Then, the sheet | seat which consists of aluminum foil of a printing base material and the electrolyte layer 4 was rolled by using the roll press machine with a roll gap of 10 micrometers, and the electrolyte layer 4 of the state peeled from the aluminum foil was produced | generated. The thickness of the electrolyte layer 4 after pressing was around 80 μm.

[Production of solid battery]
The sheet comprising the negative electrode structure and the electrolyte layer 5 was respectively punched with a Thomson blade, and the electrolyte layer 4 of the sheet and the positive electrode layer 3 of the positive electrode structure were bonded together by a dry lamination method using a roll press machine with a roll gap of 50 μm. . After that, the laminate is vacuum-sealed in an aluminum laminate bag, and irradiated with an electron beam at an acceleration voltage of 500 kV and a dose of 50 kGy using an EBC800-35 made by NHV Corporation under a nitrogen stream, to the positive electrode layer 3 and the electrolyte layer 4. Chemical crosslinking of the contained EPDM was performed. A negative electrode layer 5 punched into a fixed shape with a Thomson blade is overlaid on the obtained positive electrode-electrolyte assembly, and bonded together by a dry lamination method using a roll press machine with a roll gap of 50 μm to produce an electrode assembly. A solid battery was manufactured by placing an aluminum laminate on the outer package and heat-vacuum-sealing.

[Example 2]
[Generation of positive electrode structure]
After producing the positive electrode structure by the same process as in Example 1, it was sealed in an aluminum laminate bag and irradiated with an electron beam with an acceleration voltage of 500 kV and a dose of 50 kGy using EBC800-35 made by NHV Corporation under a nitrogen stream. The cross-linked positive electrode layer 3 was produced by performing chemical cross-linking of EPDM contained in the positive electrode layer 3 and the electrolyte layer 4 four times.
[Formation of negative electrode layer]
A negative electrode structure was produced by the same process as in Example 1.
[Creation of electrolyte layer]
An electrolyte layer was formed on the positive electrode structure on the cross-linked positive electrode layer 3 by the same process as in Example 1. At this time, the EPDM contained in the positive electrode layer 3 is usually soluble in xylene contained in the electrolyte layer coating solution. However, since the EPDM in the positive electrode layer is cross-linked by an electron beam, it does not dissolve in each other. Layer 3 and the electrolyte layer could form respective layers. The electrolyte layer-positive electrode assembly obtained here was again irradiated with an electron beam in the same manner as in the production of the positive electrode structure to produce a crosslinked electrolyte layer-positive electrode assembly.
[Production of solid battery]
After the sheets comprising the negative electrode structure and the electrolyte layer-positive electrode assembly are punched with a Thomson blade and stacked, the electrolyte layer-positive electrode assembly and the negative electrode layer 5 are dry-laminated using a roll press with a roll gap of 50 μm. Was pasted together. An aluminum laminate was arranged as an exterior body, and the obtained electrode assembly was heated and vacuum-sealed to produce a solid battery.

[Example 3]
[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 by the same process as in Example 1.
[Creation of electrolyte layer]
An electrolyte layer was formed by the same process as in Example 1.
[Production of solid battery]
Each sheet of the negative electrode structure, the positive electrode structure, and the electrolyte layer 5 is punched with a Thomson blade, and the electrode assembly disposed so as to be sandwiched by the negative electrode structure of the positive electrode structure from both sides around the electrolyte layer 4 is rolled. Bonding was performed by a dry lamination method using a roll press with a gap of 50 μm. Thereafter, an aluminum laminate as an outer package was placed on the electrode laminate, and then heat vacuum sealing was performed to produce a solid battery. The obtained solid battery was irradiated with an electron beam at an acceleration voltage of 500 kV and a dose of 50 kGy six times using an EBC800-35 manufactured by NHV Corporation under a nitrogen stream, and the EPDM contained in the positive electrode layer 3, the electrolyte layer 4 and the negative electrode layer 5. Chemical crosslinking was performed.

[Comparative Example 1]
A single cell of a solid battery was produced by the same process as in Example 1 except that the electron beam irradiation was not performed.

[Comparative Example 2]
A single cell of a solid battery was produced by the same process as Example 2 except that the electron beam irradiation was not performed in the production of the positive electrode layer.

[Internal short circuit during charging]
The single cell of Example 1 was charged with 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 0.0V, 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. FIG. 2 shows these results. 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. In FIG. 2, since there is a short circuit, a two-cell test was performed to confirm reproducibility.

  As compared with Example 1, in Comparative Example 1, when the charging current value is increased, a smile internal short circuit occurs due to lithium dendrite precipitation, the voltage becomes unstable, and the battery becomes defective. As compared with Example 2, in Comparative Example 2, when the charging current value is increased, a smile internal short circuit occurs due to lithium dendrite precipitation, the voltage becomes unstable, and the battery becomes defective.

  In addition, a battery having an open circuit voltage of 0 V immediately after the production was regarded as a voltage failure, and the number of failures when 10 pieces were produced is shown in the table. In Examples 1 and 2 and Comparative Example 2, a yield rate of about 80% was obtained, but in Example 2, the yield rate was slightly low, probably because an electrolyte layer was formed on the positive electrode. However, in Comparative Example 2 in which the electrolyte layer was formed on the positive electrode layer in the same manner as in Example 2 without electron beam crosslinking, most of the samples were initially defective. This was considered because each binder was solubilized in xylene, which is a common solvent, when the electrolyte layer was formed, and a part of the positive electrode was mixed with the electrolyte layer. Further, in comparison with this, it was found that in Example 2, the yield rate was significantly increased and the battery characteristics were improved by crosslinking the positive electrode.

  Table 2 shows the AC resistance value and capacity retention rate at 0.1 Hz after initial charging and after 10 cycles. As is clear from the table, it is clear that although there is little capacity deterioration due to charge / discharge and an increase in resistance is observed, it is suppressed more than in the comparative example. The reason why the capacity retention rate of the example is high is that the ion conduction and electron conduction paths inside the electrode are maintained by crosslinking of the binder due to expansion and contraction accompanying the insertion / extraction of lithium ions in the electrode layer during charging / discharging. This is probably because of this.

  Whether the binder could be cross-linked by electron beam irradiation was investigated using EPDM used in the examples and styrene-butadiene-styrene block copolymer (hereinafter abbreviated as SBS). As the investigation method, each polymer is dissolved in xylene, casted, and electron beam irradiation is performed under nitrogen flow, using EBC800-35 manufactured by NHV Corporation, and multiple electron beam irradiations with an acceleration voltage of 500 kV and a dose of 50 kGy. The measurement was repeated once to investigate the solubility or swelling in xylene at each cumulative dose. The results are shown in Table 3.

  With respect to xylene, which is a good solvent, SBS was dissolved up to 100 kGy, and was further insolubilized by increasing the dose, and a tendency for the degree of swelling to decrease was observed. That is, it was confirmed that chemical crosslinking proceeds when SBS is irradiated with a dose of 200 kGy or more. On the other hand, EPDM cross-linked more easily than SBS, and became insoluble by irradiation with 50 kGy, and a tendency to decrease the degree of swelling with respect to the solvent was observed in the same manner as SBS by increasing the irradiation dose. The difference in the degree of swelling between the two polymers was thought to be due to the difference in the abundance ratio of diene units contained in the molecule. In order to have a more rigid cross-linked structure, it can be said that EPDM is preferable to SBS.

  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. 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 (10)

A positive electrode;
A negative electrode,
An electrolyte layer provided between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte;
With
Any of the positive electrode, the negative electrode, and the electrolyte layer contains a hydrocarbon polymer,
The hydrocarbon polymer has a crosslinked structure,
Solid battery.   The solid battery according to claim 1, wherein the hydrocarbon-based polymer has an alkane or alkene as a main chain and is crosslinked at a part of the main chains.   3. The solid state battery according to claim 1, wherein after forming a film for forming the positive electrode, the negative electrode, or the electrolyte, the hydrocarbon compound is cross-linked to be insoluble or hardly soluble in a solvent.   The solid battery according to any one of claims 1 to 3, wherein the activation for crosslinking of the hydrocarbon polymer is performed by electron beam polymerization or thermal polymerization.   The solid battery according to claim 4, wherein the activation treatment is performed in a state where the positive electrode, the negative electrode, and the electrolyte layer are overlapped.   The solid battery according to claim 1, wherein the positive electrode and the negative electrode are connected to a current collector by the crosslinked hydrocarbon polymer.   The solid battery according to claim 1, wherein the hydrocarbon polymer is contained as a binder in at least one of the positive electrode, the negative electrode, and the electrolyte layer.   The solid battery according to claim 1, wherein the hydrocarbon polymer is contained in the electrolyte layer.   The solid battery according to claim 8, wherein the hydrocarbon contained in the electrolyte layer penetrates and crosslinks the positive electrode and / or the negative electrode. A method for producing a solid battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode and including a sulfide-based solid electrolyte,
A hydrocarbon polymer is contained in any of the positive electrode, the negative electrode, and the electrolyte layer,
The hydrocarbon polymer is cross-linked to form a laminated structure of the positive electrode, the negative electrode, and the electrolyte.
A method for producing a solid state battery.