JP2013127873A - Solid-state battery negative electrode and solid-state battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a novel and improved solid-state battery negative electrode capable of being firmly bound to a collector member and an electrolyte layer; and a solid-state battery including the solid-state battery negative electrode.SOLUTION: In order to solve the problem, according to the structure of the present invention, there is provided a solid-state battery negative electrode including: a first binding agent bound to an electrolyte layer and inactive against a solid electrolyte; a second binding agent having more excellent binding properties to a negative electrode collector member than the first binding agent; and a negative electrode active material.

Description

  The present invention relates to a negative electrode for a solid battery and a solid battery.

  For example, as disclosed in Patent Documents 1 to 4, a solid battery using a solid electrolyte is known as a lithium ion secondary battery. Such a solid battery includes an electrolyte layer containing a solid electrolyte, electrodes (positive electrode and negative electrode) formed on both surfaces of the electrolyte layer, and a current collecting member joined 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 collecting members, 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 solution for each layer, and this coating solution is sequentially applied on the current collecting member 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.

  By the way, in the manufacturing method by coating, when the solid electrolyte has a high reactivity like the sulfide-based solid electrolyte, there is a problem that the characteristics of the solid battery are deteriorated. Specifically, the sulfide-based solid electrolyte is deteriorated by reacting with a binder or a solvent used in an electrode of a lithium ion secondary battery using a non-aqueous electrolyte as an electrolyte. For this reason, conventionally, the negative electrode was produced using a nonpolar binder.

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

  However, since the non-polar binder does not sufficiently bind the negative electrode and the current collecting member, there is a problem that the current collecting member peels from the negative electrode during rolling or the like.

  In the techniques disclosed in Patent Documents 2 and 3, the negative electrode does not include a solid electrolyte. However, in these techniques, since the material of the negative electrode is limited to the metal foil, the above problem that the material of the negative electrode is limited cannot be fundamentally solved. Furthermore, even with these techniques, the binding property between the current collecting member and the negative electrode is still insufficient.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is for a new and improved solid battery that can be firmly bonded to a current collecting member and an electrolyte layer. An object of the present invention is to provide a solid battery using a negative electrode and a negative electrode for a solid battery.

  In order to solve the above-described problem, according to one aspect of the present invention, a first binder that is bound to an electrolyte layer containing a solid electrolyte and is inert to the solid electrolyte is bound to a negative electrode current collector. A negative electrode for a solid battery is provided, comprising a second binder having better adhesion than the first binder, and a negative electrode active material.

  According to this aspect, since the first binder is bound to the electrolyte layer and the second binder is bound to the negative electrode current collecting member, the solid battery negative electrode is attached to the negative electrode current collecting member and the electrolyte layer. It can be firmly bound.

  Here, the negative electrode active material may be a graphite-based active material.

  According to this aspect, even when the second binder and the sulfide solid electrolyte react in the solid battery negative electrode, the deterioration of the solid battery is prevented.

  Moreover, the 1st binder may be comprised with the nonpolar resin which does not have a polar functional group.

  According to this aspect, since the first binder is composed of a nonpolar resin having no polar functional group, the first binder can be firmly bound to the electrolyte layer.

  The second binder may be composed of a polar functional group-containing resin having a polar functional group.

  According to this aspect, since the second binder is composed of a polar functional group-containing resin having a polar functional group, it can be firmly bound by the negative electrode current collector.

  According to another aspect of the present invention, there is provided a solid state battery comprising the above negative electrode for a solid state battery and an electrolyte layer containing a solid electrolyte and an electrolyte layer binder.

  According to this aspect, since the solid battery negative electrode is firmly bound to the negative electrode current collector and the electrolyte layer, the characteristics of the solid battery are improved.

  Here, the electrolyte layer binder may contain a first binder.

  According to this aspect, the first binder in the negative electrode for a solid battery is firmly bound by the electrolyte layer.

  Further, the solid electrolyte may be a sulfide-based solid electrolyte.

  According to this viewpoint, the characteristics of the solid battery including the sulfide-based solid electrolyte can be improved.

  As described above, according to the present invention, since the first binder is bound to the electrolyte layer and the second binder is bound to the negative electrode current collector, the negative electrode for the solid battery is the negative electrode current collector. It can be firmly bound to the member and the electrolyte layer.

It is sectional drawing which shows the structure of the solid battery which concerns on embodiment of this invention. It is a graph which compares and shows the single cell thickness of an Example and a comparative example. It is a graph which compares and shows the single cell capacity density of an Example and a comparative example. It is a graph which compares and shows the impedance actual component Z 'in 1kHz of 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 addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.
<1. Structure of solid 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 collecting member 2, an adhesive layer 3, a positive electrode layer 4, an electrolyte layer 5, a negative electrode layer 6, and a negative electrode current collecting band 7. The positive electrode 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 collecting member 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. The sulfide size solid electrolyte is considered to be active against acids, alcohols, amines, ethers and the like. The first binder is bound to the positive electrode layer 4. Here, when the first binder is included in the positive electrode layer 4, 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 binder, 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-based thermoplastic elastomers such as SBS (styrene butadiene block polymer), SEBS (styrene ethylene butadiene styrene block polymer), styrene-styrene butadiene-styrene block polymer, and SBR. (Styrene butadiene rubber), BR (butadiene rubber), NR (natural rubber), IR (isoprene rubber), EPDM (ethylene-propylene-diene terpolymer) and partial hydrides or complete hydrides thereof. Can be mentioned. 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. The binder having excellent binding properties to the positive electrode current collector 2 is obtained by, for example, applying a binder solution to the positive electrode current collector 2 and drying the binder film obtained by drying the positive electrode current collector 2. The force required to peel from the member 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 member 2 through hydrogen bonds. 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), and partially hydrides or complete hydrides thereof, copolymers of polyacrylate esters, PVDF (polyvinylidene fluoride). Ride), VDF-HFP (vinylidene fluoride-hexafluoropropylene copolymer) and their carboxylic acid modified products, CM (chlorinated polyethylene), polymethacrylate, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyimide , Polyamide, polyamideimide and the like. Moreover, the polymer etc. which copolymerized the monomer which has carboxylic acid, a sulfonic acid, phosphoric acid etc. to said 1st binder are mentioned. Note that the ratio of the contents 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 50 to 95% by mass with respect to the total mass of the adhesive layer 3, and the first binder is 3 to 30% by mass with respect to the total mass of the adhesive layer 3, and the second binder. The agent should just contain 2-20 mass% with respect to the gross mass of the contact bonding layer 3. FIG.

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. As the positive electrode layer conductive material, the same material as the adhesive layer conductive material can be used. Examples of the sulfide-based solid electrolyte include Li ₂ S—P ₂ S ₅ . This sulfur-based solid electrolyte is known to have higher lithium ion conductivity than other inorganic compounds. In addition to Li ₂ S and P ₂ S ₅ , sulfur such as SiS ₂ , GeS ₂ , B ₂ S _3, etc. It may contain things. In addition, the solid electrolyte layer, as appropriate, may be used Li ₃ PO ₄ and a halogen, an inorganic solid electrolyte with added halogen compounds.

In addition, the sulfur-based solid electrolyte is heated to a temperature higher than the temperature at which both of Li ₂ S and P ₂ S ₅ are melted, melted and mixed at a predetermined ratio, held for a predetermined time, and then rapidly cooled. Can be obtained (melt quenching method). Further, a sulfide containing Li ₂ S and _P 2 _{S 5} can be obtained by treating the mechanical milling (MM) method. The mixing ratio of the Li ₂ S and the sulfide containing 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, since the electrolyte is composed of a solid electrolyte, the positive electrode layer 4 also includes a solid electrolyte. In addition, this inventor discovered that even if it did not include a solid electrolyte in the negative electrode layer 6, the performance of the solid battery 1 became favorable (refer the Example mentioned later). Therefore, the negative electrode layer 6 may not contain a solid electrolyte. Examples of the solid electrolyte constituting the positive electrode layer 4 include those containing a lithium ion conductor made of an inorganic compound as an inorganic solid electrolyte in addition to a 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 2 O-Al 2 O 3} -TiO 2 -P 2 O 5 (LATP) , and the like. 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. As the positive electrode layer binder, for example, SBS (styrene butadiene block polymer), SEBS (styrene ethylene butadiene styrene block polymer), styrene-based thermoplastic elastomers such as styrene- (styrene butadiene) -styrene block polymer, SBR (styrene butadiene rubber), BR (butadiene rubber), NR (natural rubber), IR (isoprene rubber), EPDM (ethylene-propylene-diene terpolymer) and partial hydrides or complete hydrides thereof Etc. Other examples include polystyrene, polyolefin, olefinic thermoplastic elastomer, polycycloolefin, and silicone resin. The positive electrode layer binder preferably contains a first binder.

  That is, in this embodiment, since a highly reactive sulfide-based solid electrolyte is used as the electrolyte of the solid battery 1, a non-polar resin is used as the positive electrode layer binder as in the first binder. To do. Therefore, even if the positive electrode layer 4 is directly bonded to the positive electrode current collector 2, the positive electrode layer 4 may not be sufficiently bonded to the positive electrode current collector 2. Therefore, in the present embodiment, 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. Thereby, 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 collecting member 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. By interdiffusion with the binder 1, the positive electrode layer 4 can be firmly bound.

  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. 4 to 1 mass% with respect to the total mass of 4, and the positive electrode layer binder should just contain 0.5 to 4 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 layer binder. The electrolyte layer binder is a nonpolar resin having no polar functional group. Therefore, the electrolyte layer binder is inactive to highly reactive solid electrolytes, particularly sulfide-based solid electrolytes. Examples of the electrolyte layer binder include styrene thermoplastic elastomers such as SBS (styrene butadiene block polymer), SEBS (styrene ethylene butadiene styrene block polymer), and styrene- (styrene butadiene) -styrene block polymer. SBR (styrene butadiene rubber), BR (butadiene rubber), NR (natural rubber), IR (isoprene rubber), EPDM (ethylene-propylene-diene terpolymer) and partial hydrides or complete hydrides thereof Etc. Other examples include polystyrene, polyolefin, olefinic thermoplastic elastomer, polycycloolefin, and silicone resin. The electrolyte layer binder preferably includes a first binder.

  When the electrolyte layer binder contains the first binder, the first binder in the electrolyte layer 5 is the first binder in the positive electrode layer 4 through the interface between the positive electrode layer 4 and the electrolyte layer 5. By interdiffusion with the agent, the positive electrode layer 4 is firmly bound. The ratio of the content of the sulfide-based solid electrolyte and the electrolyte layer binder is not particularly limited. For example, the sulfide-based solid electrolyte may contain 95 to 99% by mass with respect to the total mass of the electrolyte layer 5, and the electrolyte layer binder may contain 0.5 to 5% by 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, 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.

  In addition, in the negative electrode layer 6, there is a possibility that the sulfide-based solid electrolyte swells 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, the present inventor has found that the characteristics of the solid battery 1 are improved when the negative electrode active material is a graphite active material (see Examples). That is, the deterioration of the solid battery 1 is prevented. This means that if the negative electrode active material is a graphite active material, the negative electrode layer 6 does not require a sulfide-based solid electrolyte. In addition, it is guessed that a sulfide type solid electrolyte does not swell to the interface part of the negative electrode layer 6 and the negative electrode current collection member 7. FIG.

  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 hydrogen bonds. 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 in addition to the second binder. Thereby, the first binder is firmly bound to the electrolyte layer 5. When the first binder is included in the electrolyte layer 5, the first binder in the negative electrode layer 6 passes through the interface between the negative electrode layer 6 and the electrolyte layer 5. By interdiffusion with the adhesive, the electrolyte layer 5 can be more firmly bound.

  Note that 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 should just contain 0.5-5 mass% with respect to the gross mass of the negative electrode layer 6. FIG.

  As long as the negative electrode current collection member 7 is a conductor, what kind of thing may be sufficient, for example, it is comprised with aluminum, copper, stainless steel, nickel plating steel, etc. 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, an adhesive including a first binder, a second binder, an adhesive layer conductive material, and a first solvent that dissolves the first binder and the second binder. A layer coating solution 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, and a second solvent that dissolves 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 and the 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 graphite active material as 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 layer binder, and a second solvent is generated. The second solvent dissolves the electrolyte layer binder and the 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.

<3. 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]
[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 collecting member having a thickness of 20 μm is placed as a positive electrode current collecting member 2 on a desktop screen printing machine (manufactured by Neuron Ring Seimitsu Kogyo Co., Ltd., hereinafter the same), and an adhesive layer coating solution is used using a 400 mesh screen. Was coated on an aluminum foil current collecting member. 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 vapor-grown carbon as a conductive aid The fiber powder was weighed at a mass% ratio of 60: 35: 5 and mixed using a rotation and revolution mixer.

  Next, in this mixed powder, a xylene solution in which hydrogenated NBR (hereinafter referred to as Binder C) (hereinafter, Lancers Therban A3907, the same shall apply hereinafter) as a positive electrode layer binder was dissolved was used. The primary mixed solution was adjusted by adding so as to be 1% by mass. Furthermore, a xylene solution in which the binder A as the positive electrode layer binder is dissolved is added to the mixed solution so that the binder A is 0.5 mass% with respect to the total mass of the mixed powder. A secondary mixture was prepared. Furthermore, an appropriate amount of dehydrated xylene for viscosity adjustment was added to this secondary mixture to produce a tertiary mixture. Furthermore, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is changed into a tertiary mixed liquid 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 quaternary mixed solution thus produced was put into a rotation and revolution mixer, and stirred at 3000 rpm for 3 minutes to produce a positive electrode layer coating solution.

  Subsequently, the sheet | seat which consists of the positive electrode current collection member 2 and the contact bonding layer 3 was mounted in the desktop 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 current collection member 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]
96. Graphite powder (which was vacuum-dried at 80 ° C. for 24 hours) as a negative electrode active material, binder A as a first binder, and binder B as a second binder. Weighed at a mass ratio of 5: 0.5: 3.0. 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 copper foil current collecting member having a thickness of 16 μm was prepared as the negative electrode current collecting member 7, and the negative electrode layer coating solution was applied onto the copper foil current collecting member 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 housed in a dryer heated to 80 ° C. and dried for 15 minutes. Further, the dried sheet was vacuum dried at 80 ° C. for 24 hours. Thereby, the negative electrode layer 6 was produced. Note that a negative electrode sheet corresponding to the negative electrode layer 6 may be generated by the same process as that for the adhesive film and may be pressure-bonded to the negative electrode current collecting member 7.

  Subsequently, 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 100 μm.

[Creation of electrolyte layer]
Lithium ₂ S—P ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte is mixed with a xylene solution of binder C (electrolyte layer binder) and binder C is amorphous. The primary mixed liquid was adjusted by adding so as to be 1% by mass with respect to the mass of the fine powder. Furthermore, by adding a xylene solution of binder A (electrolyte layer binder) to this mixture so that binder A is 0.5 mass% with respect to the mass of the amorphous powder, A secondary mixture was prepared. Furthermore, an appropriate amount of dehydrated xylene for viscosity adjustment was added to this secondary mixture to produce a tertiary mixture. Furthermore, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is changed into a tertiary mixed liquid 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 quaternary mixed solution thus produced 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 of the sheet 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.

[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]
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 Vapor growth carbon fiber powder as an agent was weighed in a mass% ratio of 60: 35: 5 and mixed using a rotation and revolution mixer.

  Next, by adding a xylene solution of the binder C (first binder) to the mixed powder so that the binder C is 2.0% by mass with respect to the total mass of the mixed powder, A primary mixture was prepared. 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 tertiary mixed liquid 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, a 16 μm-thick copper foil current collecting member as a negative electrode current collecting member was placed on a desktop screen printing machine, and a negative electrode layer coating solution was applied onto the negative electrode current collecting member using a 150 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. Subsequently, the sheet | seat which consists of a negative electrode current collection member and a negative electrode layer was rolled using the roll press machine with a roll gap of 50 micrometers, and the negative electrode structure was produced | generated. The thickness of the negative electrode structure was around 125 μm.

[Creation of electrolyte layer]
Li ₂ S—P ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte is mixed with a xylene solution of hydrogenated SBR (hereinafter, binder D) (electrolyte layer binder). The primary liquid mixture was adjusted by adding the binder D so that it might become 1.5 mass% with respect to the mass of an amorphous powder. Furthermore, a secondary mixed solution was generated by adding an appropriate amount of dehydrated xylene for viscosity adjustment to this mixed solution. Further, in order to improve the dispersibility of the amorphous powder, the zirconia balls having a diameter of 5 mm are arranged so that the space, the amorphous powder, and the zirconia balls each occupy 1/3 of the total volume of the kneading container. It poured into the next liquid mixture. 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. As a result, an electrolyte layer was formed on the negative electrode structure. The total thickness of the negative electrode structure and the electrolyte layer after drying was around 130 μm.

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

[Thickness measurement]
The thickness of the single cell of Example 1 (thickness excluding the exterior laminate portion. The same applies to Comparative Example 1) was 287 μm. On the other hand, the thickness of the single cell of Comparative Example 1 was 493 μm. FIG. 2 shows a graph comparing these.

[Capacity density measurement]
The capacity density (Ah / kg) of the single cell of Example 1 and the capacity density (Ah / kg) of the single cell of Comparative Example 1 were measured with a charge / discharge evaluation apparatus TOSCAT-3100 manufactured by Toyo System. As a result, the capacity density of the single cell of Example 1 was 24.6 (Ah / kg), and the capacity density of the single cell of Comparative Example 1 was 16.5 (Ah / kg). FIG. 3 shows a graph comparing these.

[Impedance measurement]
The single cells of Example 1 and Comparative Example 1 were charged under the condition of a current density of 0.05 mA / cm ^{2 in} a 25 ° C. thermostat until the voltage reached 4 V, and then the impedance at 1 kHz in the 25 ° C. thermostat. Was measured as the resistance of the solid battery. The measurement was performed with an AUTOLAB impedance analyzer. As a result, the actual impedance component Z ′ of Example 1 was 4.84 (Ω), and the actual impedance component Z ′ of Comparative Example 1 was 8.08 (Ω). FIG. 4 shows a graph comparing these.

[Evaluation]
According to the above measurement results, the single cell of Example 1 has a higher filling (thickness is smaller) than the single cell of Comparative Example 1, and the energy density and actual impedance component Z ′ are higher than those of the single cell of Comparative Example 1. Is also big. That is, the characteristics of the single cell of Example 1 are greatly improved as compared with the single cell of Comparative Example 1.

  In Comparative Example 1, since the second binder is not included in the negative electrode layer, the binding property between the negative electrode layer and the negative electrode current collector is poor. Furthermore, since the first binder (binder D) in the negative electrode layer and the electrolyte layer binder (binder C) are different, the binding between the negative electrode layer and the electrolyte layer is also poor. On the other hand, in Example 1, since the negative electrode layer 6 contains the second binder, the binding property between the negative electrode layer 6 and the negative electrode current collector 7 is good. Furthermore, since the electrolyte layer binder (binder C, binder A) includes the first binder (binder A) in the negative electrode layer 6, the negative electrode layer 6 and the electrolyte layer 5 The binding property is also good. For these reasons, it is considered that the characteristics of the single cell of Example 1 are greatly improved as compared with the single cell of Comparative Example 1. Table 1 summarizes the materials and evaluations of Example 1 and Comparative Example 1.

  As described above, the negative electrode layer 6 of the present embodiment, that is, the negative electrode 20 is bound to the electrolyte layer 5 containing the sulfide-based solid electrolyte, and the first binder that is inactive to the solid electrolyte and the negative electrode current collector. The negative electrode active material and the 2nd binder whose binding property to the member 7 is superior to the 1st binder are included. Therefore, since the first binder is bound to the electrolyte layer 5 and the second binder is bound to the negative electrode current collector member 7, the negative electrode 20 is firmly attached to the negative electrode current collector member 7 and the electrolyte layer 5. Can be bound.

  Furthermore, since the negative electrode active material is a graphite-based active material, even if the sulfide-based solid electrolyte reacts with the second binder in the negative electrode 20, deterioration of the solid battery 1 is prevented. That is, no sulfide-based solid electrolyte is required for the negative electrode 20.

  Further, since the first binder is composed of a nonpolar resin having no polar functional group, the first binder can be firmly bound by the electrolyte layer 5.

  Further, since the second binder is composed of a polar functional group-containing resin having a polar functional group, it can be firmly bound by the negative electrode current collector member 7.

  Furthermore, since the electrolyte layer binder contains the first binder, the first binder in the negative electrode 20 can be firmly bound to the electrolyte layer 5.

  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 or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Solid battery 2 Positive electrode current collection member 3 Adhesion layer 4 Positive electrode layer 5 Electrolyte layer 6 Negative electrode layer 7 Negative electrode current collection member

Claims (7)

  A second binder that binds to an electrolyte layer containing a solid electrolyte and is more inert than the first binder and has a binding property to the negative electrode current collector that is inert to the solid electrolyte. A negative electrode for a solid battery, comprising: a binder as described above; and a negative electrode active material.   The negative electrode for a solid battery according to claim 1, wherein the negative electrode active material is a graphite-based active material.   The negative electrode for a solid battery according to claim 1 or 2, wherein the first binder is composed of a nonpolar resin having no polar functional group.   The electrode for a solid battery according to any one of claims 1 to 3, wherein the second binder is made of a polar functional group-containing resin having a polar functional group.   A solid battery comprising the negative electrode for a solid battery according to claim 1, and an electrolyte layer containing a solid electrolyte and an electrolyte layer binder.   The solid electrolyte battery according to claim 5, wherein the electrolyte layer binder includes a first binder. The solid battery electrode according to claim 5 or 6, wherein the solid electrolyte is a sulfide solid electrolyte.

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