JP7296302B2 - All-solid battery - Google Patents

Description

The present invention relates to all-solid-state batteries.

In recent years, in order to cope with global warming, reduction of the amount of carbon dioxide is earnestly desired. In the automobile industry, expectations are gathering for the reduction of carbon dioxide emissions through the introduction of electric vehicles (EV) and hybrid electric vehicles (HEV). Development of electrolyte secondary batteries has been actively carried out.

Secondary batteries for motor driving are required to have extremely high output characteristics and high energy compared to consumer lithium-ion secondary batteries used in mobile phones, notebook computers, and the like. Therefore, lithium-ion secondary batteries, which have the highest theoretical energy among all practical batteries, have attracted attention and are being rapidly developed.

Lithium ion secondary batteries, which are currently in widespread use, use a combustible organic electrolyte as an electrolyte. Such a liquid-type lithium ion secondary battery requires stricter safety measures against liquid leakage, short circuit, overcharge, etc. than other batteries.

Therefore, in recent years, research and development on all-solid-state batteries such as all-solid-state lithium-ion secondary batteries using oxide-based or sulfide-based solid electrolytes have been actively carried out. A solid electrolyte is a material composed mainly of an ionic conductor capable of conducting ions in a solid. Therefore, in all-solid-state lithium ion secondary batteries, in principle, various problems due to combustible organic electrolytes do not occur unlike conventional liquid-type lithium ion secondary batteries. In general, the use of a high-potential, large-capacity positive electrode material and a large-capacity negative electrode material can significantly improve the output density and energy density of the battery. All-solid-state lithium-ion secondary batteries using elemental sulfur (S) or sulfide-based materials as positive electrode active materials are promising candidates.

Here, the solid electrolyte layer that constitutes the all-solid-state battery, unlike the separator that constitutes the liquid-based battery, can be formed on the surface of either the positive or negative electrode active material layer by a method such as a coating method or a vapor deposition method. be. A solid electrolyte layer formed by such a method can be thinned. As a result, the ohmic resistance in the solid electrolyte layer can be reduced, and the cell volume can also be reduced, which is advantageous for increasing the output and capacity of the all-solid-state battery.

On the other hand, according to the method of forming the solid electrolyte layer as described above, the solid electrolyte layer cannot exist as a self-supporting film. must be endorsed by Therefore, when the all-solid-state battery is viewed from above, the outer peripheral edge of the solid electrolyte layer coincides with the outer peripheral edge of the active material layer serving as the underlying layer.

By the way, in a lithium ion secondary battery, the negative electrode potential decreases as the charging progresses. When the negative electrode potential drops below 0 V (vs. Li/Li+), metallic lithium precipitates on the negative electrode and dendrite (dendritic) crystals precipitate (this phenomenon is also referred to as metallic lithium electrodeposition). In particular, in an all-solid-state battery using metallic lithium or a lithium-containing alloy as a negative electrode active material, the electrodeposition of metallic lithium is the charging reaction itself. Here, when excessive electrodeposition of metallic lithium occurs in an all-solid-state battery, the deposited dendrite may penetrate the solid electrolyte layer and cause internal short-circuiting of the battery.

For the purpose of preventing such electrodeposition of metallic lithium in an all-solid-state battery, for example, Patent Document 1 discloses that the interface between a solid electrolyte layer and a negative electrode active material layer is stabilized for a long period of time to allow the electrodeposition of metallic lithium. For the purpose of preventing the occurrence of an internal short circuit due to sedimentation, a technique has been disclosed in which a sacrificial layer is provided between these layers and is made of a material that has lithium ion conductivity and can be alloyed with the negative electrode active material layer. there is

U.S. Patent Application Publication No. 2018/0123181

Here, with the technique disclosed in Patent Document 1, the contact resistance between the solid electrolyte layer and the negative electrode active material layer cannot be sufficiently reduced, and the internal resistance of the battery may increase. .

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide means for minimizing the increase in contact resistance between a solid electrolyte layer and a negative electrode active material layer in an all-solid-state battery, thereby preventing an increase in the internal resistance of the battery. and

The present inventors have made intensive studies to solve the above problems. As a result, in an all-solid battery containing metallic lithium or a lithium-containing alloy as a negative electrode active material and a solid electrolyte layer containing a sulfide solid electrolyte, lithium (Li), phosphorus (P), sulfur (S) and oxygen (O) and the atomic ratio (O/S ratio) of oxygen (O) atoms to sulfur (S) atoms is greater than 0.4 and less than 0.8 on the surface of the solid electrolyte layer on the negative electrode active material layer side The present inventors have found that the above-mentioned problems can be solved by providing .

That is, according to one aspect of the present invention, a positive electrode in which a positive electrode active material layer containing a positive electrode active material is disposed on the surface of the positive electrode current collector, and metallic lithium or a lithium-containing alloy is provided on the surface of the negative electrode current collector. and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a sulfide solid electrolyte. An all-solid-state battery comprising the element is provided. The solid electrolyte layer contains lithium (Li), phosphorus (P), sulfur (S) and oxygen (O) on at least part of the surface on the negative electrode active material layer side, and sulfur (S) atoms It is characterized in that it has a region in which the atomic ratio (O/S ratio) of oxygen (O) atoms with respect to is greater than 0.4 and less than 0.8.

In the solid electrolyte layer constituting the all-solid-state battery according to the present invention, the region where the O / S ratio is greater than 0.4 and less than 0.8 has a low contact resistance with the negative electrode active material layer, and lithium ions. can contribute to the uniformity of the interface because of its good wettability. Therefore, the presence of such a region on the surface of the solid electrolyte layer on the side of the negative electrode active material layer reduces the contact resistance between the solid electrolyte layer and the negative electrode active material layer, preventing an increase in the internal resistance of the battery. has the advantage of being

FIG. 1 is a perspective view showing the appearance of a flat laminated battery that is one embodiment of an all-solid-state battery according to the present invention. FIG. 2 is a cross-sectional view along line 2-2 shown in FIG. FIG. 3 is a cross-sectional view schematically showing a bipolar all-solid-state lithium-ion secondary battery (bipolar secondary battery), which is an embodiment of the all-solid-state battery according to the present invention.

One embodiment of the present invention includes a positive electrode in which a positive electrode active material layer containing a positive electrode active material is arranged on the surface of a positive electrode current collector, and a negative electrode active material layer containing metallic lithium or a lithium-containing alloy on the surface of the negative electrode current collector. A power generating element having a negative electrode on which a negative electrode active material layer containing a substance is arranged, and a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a sulfide solid electrolyte, The solid electrolyte layer contains lithium (Li), phosphorus (P), sulfur (S) and oxygen (O) on at least a part of the surface on the negative electrode active material layer side, and The all-solid battery has a region in which the atomic ratio of (O) atoms (O/S ratio) is greater than 0.4 and less than 0.8.

Hereinafter, the embodiments of the present embodiment described above will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims and is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios.

FIG. 1 is a perspective view showing the appearance of a flat laminated battery that is one embodiment of an all-solid-state battery according to the present invention. FIG. 2 is a cross-sectional view along line 2-2 shown in FIG. By using a laminate type, the battery can be made compact and have a high capacity. In the present specification, a flat laminated non-bipolar lithium ion secondary battery (hereinafter also simply referred to as a “laminated battery”) shown in FIGS. 1 and 2 will be described in detail as an example. However, when viewed from the electrical connection form (electrode structure) inside the all-solid-state battery according to this embodiment, both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries applicable.

As shown in FIG. 2, the laminated battery 10a has a rectangular flat shape, and from both sides thereof, a positive collector plate 25 and a negative collector plate 27 for extracting electric power are pulled out. there is The power generation element 21 is wrapped by the battery exterior material (laminate film 29) of the laminated battery 10a, and the periphery thereof is heat-sealed. It is sealed in the pulled out state.

In addition, the all-solid-state battery according to the present embodiment is not limited to a laminated flat shape. The wound-type all-solid-state battery may have a cylindrical shape, or may have a flat rectangular shape obtained by deforming such a cylindrical shape. It is not particularly limited. In the case of the cylindrical container, a laminate film may be used as the exterior material, or a conventional cylindrical can (metal can) may be used. Preferably, the power generation element is housed inside a laminate film containing aluminum. Weight reduction can be achieved by this configuration.

In addition, there are no particular restrictions on how the collector plates (25, 27) shown in FIG. 1 can be taken out. The positive current collecting plate 25 and the negative current collecting plate 27 may be pulled out from the same side, or the positive current collecting plate 25 and the negative current collecting plate 27 may be divided into a plurality of pieces and pulled out from each side. It is not limited to those shown in FIGS. 1 and 2, such as good. In a wound type lithium ion battery, terminals may be formed using, for example, cylindrical cans (metal cans) instead of tabs.

As shown in FIG. 2, the laminate type battery 10a of the present embodiment has a structure in which a flat and substantially rectangular power generation element 21 in which charge/discharge reactions actually progress is sealed inside a laminate film 29 that is a battery exterior material. have Here, the power generation element 21 has a structure in which a positive electrode, a solid electrolyte layer 17, and a negative electrode are laminated. In this embodiment, the solid electrolyte layer 17 contains Li ₃ PS ₄ which is one type of sulfide solid electrolyte. The positive electrode has a structure in which positive electrode active material layers 13 containing a positive electrode active material are arranged on both sides of a positive electrode current collector 11'. The negative electrode has a structure in which negative electrode active material layers 15 containing a negative electrode active material (here, metallic lithium) are arranged on both sides of a negative electrode current collector 11 ″. Specifically, one positive electrode active material layer 13 . The positive electrode, the solid electrolyte layer, and the negative electrode are laminated in this order such that the adjacent negative electrode active material layer 15 faces the solid electrolyte layer 17. As a result, the adjacent positive electrode and solid electrolyte The layer and the negative electrode constitute one single cell layer 19. Therefore, the stacked battery 10a shown in Fig. 2 has a configuration in which a plurality of single cell layers 19 are stacked and electrically connected in parallel. It can be said that

As shown in FIG. 2, the positive electrode active material layer 13 is arranged only on one side of each of the outermost positive electrode current collectors located on both outermost layers of the power generating element 21, but the active material layer is provided on both sides. may be That is, a current collector having active material layers on both sides may be used as it is as the current collector for the outermost layer, instead of using the current collector exclusively for the outermost layer having the active material layer on only one side.

The positive electrode current collector 11 and the negative electrode current collector 12 are respectively attached with a positive electrode current collector plate (tab) 25 and a negative electrode current collector plate (tab) 27 electrically connected to each electrode (positive electrode and negative electrode). It has a structure in which it is pulled out of the laminate film 29 so as to be sandwiched between the ends of the laminate film 29 . The positive electrode current collector 25 and the negative electrode current collector 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 13 of each electrode via the positive electrode lead and the negative electrode lead (not shown), respectively, as required. or resistance welding.

As described above _, the solid electrolyte layer 17 contains Li ₃ PS ₄ which is a type of sulfide solid electrolyte _. Specifically, the O/S ratio) is controlled to a specific composition (details of this "specific composition" will be described later). As a result, the contact resistance between the solid electrolyte layer and the negative electrode active material layer is reduced, and an advantage of preventing an increase in the internal resistance of the battery is obtained.

In addition, in the laminated battery 10a according to the present embodiment, the outer peripheral edge of the solid electrolyte layer 17 is arranged so as to match the outer peripheral edge of the positive electrode active material layer 13 when viewed from above. Such a configuration can be obtained by forming the solid electrolyte layer 17 on the surface of the positive electrode active material layer 13 by a technique such as coating or vapor deposition. Here, the outer peripheral end of the positive electrode current collector 11 ′ also has a solid state in plan view, except for a portion that extends outward and is electrically connected to the positive electrode current collector plate 25 . It is arranged so as to match the outer peripheral edge of the electrolyte layer 17 (and the positive electrode active material layer 13).

As described above, in this embodiment, the composition (specifically, the O/S ratio) of Li ₃ PS ₄ forming the solid electrolyte layer 17 is controlled to a specific composition. That is, the composition of Li ₃ PS ₄ (specifically, the O/S ratio) is controlled to a specific composition over the entire surface of the solid electrolyte layer 17 on the negative electrode active material layer 15 side. As a result, the outer peripheral edge of the negative electrode active material layer 15 is included in a region where the composition of Li ₃ PS ₄ (specifically, the O/S ratio) is controlled to a specific composition when viewed from above. there is With such a structure, the entire exposed surface of the negative electrode active material layer 15 exhibits excellent interfacial contact with the solid electrolyte layer, which can effectively contribute to the reduction of the internal resistance of the battery. . Furthermore, in the laminate type battery 10a according to the present embodiment, the outer peripheral edge of the negative electrode active material layer 15 is positioned inside the outer peripheral edge of the solid electrolyte layer 17 over the entire circumference. As a result, when viewed from above, the outer peripheral edge of the negative electrode active material layer 15 is included in the region in which the O/S ratio is controlled to a specific composition in the solid electrolyte layer 17 . With such a configuration, the entire surface of the negative electrode active material layer 15 involved in charge/discharge forms a good interface with the solid electrolyte layer 17, which can contribute to reducing the contact resistance.

Main constituent members of the all-solid-state battery according to the present embodiment will be described below.

[Current collector]
The current collector has a function of mediating transfer of electrons from one surface in contact with the positive electrode active material layer to the other surface in contact with the negative electrode active material layer. There are no particular restrictions on the material that constitutes the current collector. As the constituent material of the current collector, for example, a metal or a conductive resin can be used.

Specifically, metals include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or the like may be used. Alternatively, a foil in which a metal surface is coated with aluminum may be used. Among them, aluminum, stainless steel, copper, and nickel are preferable from the viewpoint of electronic conductivity, battery operating potential, adhesion of the negative electrode active material to the current collector by sputtering, and the like.

As the latter conductive resin, a resin obtained by adding a conductive filler to a non-conductive polymeric material as necessary can be used.

Examples of non-conductive polymer materials include polyethylene (PE; high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), and polyimide. (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethylacrylate (PMA), polymethylmethacrylate (PMMA) , polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such non-conductive polymeric materials can have excellent electrical potential or solvent resistance.

Conductive fillers may be added to the conductive polymer material or non-conductive polymer material as necessary. In particular, when the resin serving as the base material of the current collector consists of only a non-conductive polymer, a conductive filler is inevitably essential in order to impart conductivity to the resin.

Any electrically conductive filler can be used without particular limitation. Examples of materials having excellent conductivity, potential resistance, or lithium ion blocking properties include metals and conductive carbon. The metal is not particularly limited, but includes at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or these metals. It preferably contains alloys or metal oxides. Also, the conductive carbon is not particularly limited. Preferably, it is selected from the group consisting of acetylene black, Vulcan (registered trademark), Black Pearl (registered trademark), carbon nanofiber, Ketjenblack (registered trademark), carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. At least one type is included.

The amount of the conductive filler added is not particularly limited as long as it is an amount that can impart sufficient conductivity to the current collector, and is generally 5 to 80% by mass with respect to 100% by mass of the total mass of the current collector. is.

The current collector may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of these materials are appropriately combined. From the viewpoint of reducing the weight of the current collector, it is preferable to include at least a conductive resin layer made of a resin having conductivity. Moreover, from the viewpoint of blocking movement of lithium ions between the single cell layers, a metal layer may be provided on a part of the current collector.

[Negative electrode active material layer]
The negative electrode active material layer contains a negative electrode active material. In the present invention, the negative electrode active material essentially contains metallic lithium (Li) or a lithium-containing alloy. The types of these negative electrode active materials are not particularly limited, but lithium-containing alloys include, for example, alloys of lithium and at least one material that can be alloyed with lithium. Examples of materials that can be alloyed with lithium include Si, Au, In, Ge, Sn, Pb, Al, Zn, H, Ca, Sr, Ba, Ru, Rh, Ir, Pd, Pt, Ag, Cd, Hg, Ga, Tl, C, N, Sb, Bi, O, S, Se, Te, Cl and the like. Among these, the material that can be alloyed with lithium is at least one selected from the group consisting of Si, Au, In, Ge, Sn, Pb, Al and Zn, from the viewpoint of constructing a battery with excellent capacity and energy density. It preferably contains a seed element, more preferably Si, Au or In. In some cases, two or more kinds of negative electrode active materials may be used together. Needless to say, negative electrode active materials other than those described above may be used as long as they essentially contain metallic lithium or a lithium-containing alloy.

Examples of the shape of the negative electrode active material include particulate (spherical, fibrous), thin film, and the like, and thin film is preferred. When the negative electrode active material is in the form of particles, the average particle size (D ₅₀ ) thereof is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, and even more preferably. is in the range from 100 nm to 20 μm, particularly preferably in the range from 1 to 20 μm. In addition, in this specification, the value of the average particle diameter ( _D50 ) of the active material can be measured by a laser diffraction scattering method.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited. more preferred.

The negative electrode active material layer may further contain a solid electrolyte. By including the solid electrolyte in the negative electrode active material layer, the ion conductivity of the negative electrode active material layer can be improved. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, and sulfide solid electrolytes are preferred.

Examples of sulfide solid electrolytes include LiI—Li ₂ S—SiS ₂ , LiI—Li ₂ SP ₂ O ₅ , LiI—Li ₃ PO ₄ —P ₂ S ₅ , Li ₂ SP ₂ S ₅ , LiI _{- Li3PS4} , _{LiI - LiBr - Li3PS4 , Li3PS4 , Li2SP2S5 , Li2SP2S5} -LiI _{, Li2SP2S5-} Li ₂ O, Li ₂ SP ₂ S ₅ —Li ₂ O—LiI, Li ₂ S—SiS ₂ , Li ₂ S—SiS ₂ —LiI, Li ₂ S—SiS ₂ —LiBr, Li ₂ S—SiS ₂ -LiCl, _Li2S - _SiS2 - _{B2S3 - LiI} , _{Li2S - SiS2 - P2S5} -LiI, _Li2S - _B2S3 , _{Li2SP2S5 -} Z _m S _n (where m and n are positive numbers and Z is one of Ge, Zn and Ga), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Li _x MO _y (where x and y are positive numbers and M is any one of P, Si, Ge, B, Al, Ga and In), and the like. . The description of “Li ₂ SP ₂ S ₅ ” means a sulfide solid electrolyte using a raw material composition containing Li ₂ S and P ₂ S ₅ , and the same applies to other descriptions.

The sulfide solid electrolyte may have, for example, a Li ₃ PS ₄ skeleton, a Li ₄ P ₂ S ₇ skeleton, or a Li ₄ P ₂ S ₆ skeleton. . Examples of sulfide solid electrolytes having a Li ₃ PS ₄ skeleton include LiI--Li ₃ PS ₄ , LiI--LiBr--Li ₃ PS _{4 and} Li ₃ PS ₄ . Examples of sulfide solid electrolytes having a Li ₄ P ₂ S ₇ skeleton include Li—P—S solid electrolytes called LPS (eg, Li ₇ P ₃ S ₁₁ ). As the sulfide solid electrolyte, for example, LGPS represented by Li _(4-x) Ge _(1-x) P _x S ₄ (where x satisfies 0<x<1) may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing the element P, and more preferably a material containing Li ₂ SP ₂ S ₅ as a main component. Furthermore, the sulfide solid electrolyte may contain halogens (F, Cl, Br, I).

When the sulfide solid electrolyte is Li ₂ S—P ₂ S ₅ system, the molar ratio of Li ₂ S and P ₂ S ₅ is Li ₂ S:P ₂ S ₅ =50:50 to 100. :0, and more preferably Li ₂ S:P ₂ S ₅ =70:30 to 80:20.

The sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. The sulfide glass can be obtained, for example, by subjecting the raw material composition to mechanical milling (such as a ball mill). Crystallized sulfide glass can be obtained, for example, by heat-treating sulfide glass at a temperature equal to or higher than the crystallization temperature. Further, the ionic conductivity (eg, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25° C.) is, for example, preferably 1×10 ⁻⁵ S/cm or more, and 1×10 ⁻⁴ S/cm or more. cm or more is more preferable. Incidentally, the value of the ionic conductivity of the solid electrolyte can be measured by the AC impedance method.

Examples of oxide solid electrolytes include compounds having a NASICON structure. Examples of compounds having a NASICON structure include compounds represented by the general formula Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (0≦x≦2) (LAGP) and general formula Li _1+x Al _x Ti _{2 -x} (PO ₄ ) ₃ (0≦x≦2) (LATP) and the like. Other examples of oxide solid electrolytes include LiLaTiO (e.g., Li _0.34 La _0.51 TiO ₃ ), LiPON (e.g., Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (e.g., , Li ₇ La ₃ Zr ₂ O ₁₂ ) and the like.

Examples of the shape of the solid electrolyte include particle shapes such as spherical and ellipsoidal shapes, and thin film shapes. When the solid electrolyte is in the form of particles, the average particle size (D ₅₀ ) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. On the other hand, the average particle diameter (D ₅₀ ) is preferably 0.01 μm or more, more preferably 0.1 μm or more.

The content of the solid electrolyte in the negative electrode active material layer is, for example, preferably in the range of 0 to 60% by mass, more preferably in the range of 0 to 50% by mass.

The negative electrode active material layer may further contain at least one of a conductive aid and a binder in addition to the negative electrode active material and solid electrolyte described above.

Examples of conductive aids include metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys containing these metals, or metal oxides; carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, activated carbon fiber, etc.), carbon nanotubes (CNT), carbon black (specifically, acetylene black, Ketjenblack (registered trademark) , furnace black, channel black, thermal lamp black, etc.), but are not limited thereto. In addition, a particulate ceramic material or resin material coated with the above metal material by plating or the like can also be used as a conductive aid. Among these conductive aids, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon. , silver, gold, and carbon, and more preferably at least one carbon. These conductive aids may be used alone or in combination of two or more.

The shape of the conductive aid is preferably particulate or fibrous. When the conductive agent is particulate, the shape of the particles is not particularly limited, and may be powdery, spherical, rod-like, needle-like, plate-like, columnar, amorphous, scaly, spindle-like, or the like. I don't mind.

The average particle size (primary particle size) of the conductive additive in the form of particles is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical characteristics of the battery. In this specification, the "particle diameter of the conductive aid" means the maximum distance L among the distances between any two points on the outline of the conductive aid. The value of the "average particle size of the conductive aid" is the particle size of particles observed in several to several tens of fields using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). shall be calculated as the average value of

When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative electrode active material layer is not particularly limited, but is preferably 0 to 10% by mass with respect to the total mass of the negative electrode active material layer. , more preferably 2 to 8% by mass, more preferably 4 to 7% by mass. Within such a range, it becomes possible to form a stronger electron conduction path in the negative electrode active material layer, which can effectively contribute to the improvement of battery characteristics.

On the other hand, the binder is not particularly limited, but includes, for example, the following materials.

Polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are replaced with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, polytetrafluoroethylene, Polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and hydrogenated products thereof , thermoplastic polymers such as styrene/isoprene/styrene block copolymers and their hydrogenated products, tetrafluoroethylene/hexafluoropropylene copolymers (FEP), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymers (PFA) , ethylene/tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene/chlorotrifluoroethylene copolymer (ECTFE), fluorine resins such as polyvinyl fluoride (PVF), vinylidene fluoride- Hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluororubber (VDF-PFP-TFE fluororubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluororubber ( VDF-PFMVE-TFE fluororubber), vinylidene fluoride-chlorotrifluoroethylene fluororubber (VDF-CTFE fluororubber) and other vinylidene fluoride fluororubbers, and epoxy resins. Among them, polyimide, styrene-butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

One preferred embodiment of the negative electrode active material layer has a first active material layer containing metallic lithium or a lithium-containing alloy, and a second active material layer containing a material that can be alloyed with lithium. A material layer is disposed between the solid electrolyte layer and the first active material layer. With such a configuration, it is possible to minimize the decrease in the capacity of the negative electrode active material layer and prevent the occurrence of a short circuit due to the growth of metallic lithium dendrites in the solid electrolyte layer. Here, specific examples and preferred forms of the material that can be alloyed with lithium are as described above, and detailed description thereof will be omitted here.

Although the thickness of the negative electrode active material layer varies depending on the configuration of the intended all-solid-state battery, it is preferably in the range of 0.1 to 1000 μm, for example.

[Positive electrode active material layer]
The positive electrode active material layer contains a positive electrode active material. The type of the positive electrode active material is not particularly limited, but elemental sulfur (S ₈ ) or a reduction product of sulfur containing lithium (any of Li ₂ S ₈ to Li ₂ S compounds) is preferably used. Here, for example, elemental sulfur (S ₈ ) has an extremely large theoretical capacity of about 1670 mAh/g, and has the advantage of being low cost and abundant as a resource. In this case, when the all-solid-state battery is provided in a charged state, elemental sulfur (S ₈ ) is included as the positive electrode active material. In addition, when the all-solid-state battery is provided in a discharged state, the positive electrode active material contains a reduction product of sulfur containing lithium (any of the compounds of Li ₂ S ₈ to Li ₂ S described above). .

The positive electrode active material layer contains a positive electrode active material other than the above-described elemental sulfur (S ₈ ) or a reduction product of sulfur containing lithium (any of the compounds of Li ₂ S ₈ to Li ₂ S described above). may contain. However, the ratio of the sulfur element or the reduction product of sulfur containing lithium to the positive electrode active material contained in the positive electrode active material layer is preferably 50 to 100% by mass, more preferably 80 to 100% by mass. , More preferably 90 to 100% by mass, still more preferably 95 to 100% by mass, particularly preferably 98 to 100% by mass, most preferably 100% by mass.

Positive electrode active materials other than elemental sulfur or reduction products of sulfur containing lithium include, for example, disulfide compounds, sulfur-modified polyacrylonitrile and sulfur-modified polyisoprene represented by compounds described in WO 2010/044437 pamphlet. , rubeanic acid (dithiooxamide), carbon polysulfide, and the like. Inorganic sulfur compounds such as S-carbon composites, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , MoS ₂ and MoS ₃ can also be used. Furthermore, examples of positive electrode active materials containing no sulfur include layered rock salt type active materials such as LiCoO ₂ , LiMnO _{2 , LiNiO 2} , LiVO _{2 ,} Li(Ni—Mn—Co)O ₂ , LiMn ₂ O ₄ , LiNi spinel-type active materials such _{as 0.5Mn1.5O4} ; olivine-type active materials such _{as LiFePO4} and _{LiMnPO4 ;} and Si-containing active materials such _{as Li2FeSiO4} and _Li2MnSiO4 . As an oxide active material other than the above, for example, Li ₄ Ti ₅ O ₁₂ can be mentioned. In some cases, two or more positive electrode active materials may be used together. It goes without saying that positive electrode active materials other than those described above may be used.

Examples of the shape of the positive electrode active material include particulate (spherical, fibrous), thin film, and the like. When the positive electrode active material is in the form of particles, its average particle size (D ₅₀ ) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, and still more preferably 100 nm. to 20 μm, particularly preferably 1 to 20 μm. In addition, in this specification, the value of the average particle diameter ( _D50 ) of the active material can be measured by a laser diffraction scattering method.

The content of the positive electrode active material in the positive electrode active material layer is not particularly limited. more preferred.

The positive electrode active material layer may also further contain a conductive aid and/or a binder, similar to the negative electrode active material layer.

[Solid electrolyte layer]
The solid electrolyte layer of the all-solid-state battery according to the present embodiment is a layer containing a solid electrolyte as a main component and interposed between the positive electrode active material layer and the negative electrode active material layer described above. Moreover, the solid electrolyte layer of the all-solid-state battery according to the present embodiment essentially contains a sulfide solid electrolyte, but may contain other solid electrolytes. However, the proportion of the sulfide solid electrolyte in the solid electrolyte contained in the solid electrolyte layer is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass. Yes, more preferably 95 to 100% by mass, particularly preferably 98 to 100% by mass, most preferably 100% by mass. Since the specific forms of the sulfide solid electrolyte and other solid electrolytes contained in the solid electrolyte layer are the same as those described above, detailed description thereof is omitted here.

The content of the solid electrolyte in the solid electrolyte layer is, for example, preferably in the range of 10 to 100% by mass, more preferably in the range of 50 to 100% by mass, and in the range of 90 to 100% by mass. is more preferable.

The solid electrolyte layer may further contain a binder in addition to the solid electrolyte described above. Since the specific form of the binder that can be contained in the solid electrolyte layer is the same as described above, detailed description is omitted here.

The thickness of the solid electrolyte layer varies depending on the configuration of the intended all-solid-state battery.

(Region where O/S ratio is controlled)
As described above, in the all-solid-state battery according to this embodiment, the composition (specifically, the O/S ratio) of Li ₃ PS ₄ constituting the solid electrolyte layer 17 is controlled to a specific composition. Specifically, in this embodiment, the solid electrolyte forming the solid electrolyte layer 17 is based on Li ₃ PS ₄ . However, sulfide solid electrolytes generally inevitably contain a certain amount of oxygen (O) atoms during the manufacturing process. Therefore, the solid electrolyte forming the solid electrolyte layer 17 inevitably contains oxygen (O) atoms in addition to lithium (Li), phosphorus (P) and sulfur (S). That is, in the all-solid-state battery according to this embodiment, the solid electrolyte layer 17 essentially contains lithium (Li), phosphorus (P), sulfur (S) and oxygen (O). In the stacked battery 10a according to the embodiment shown in FIGS. 1 and 2, the solid electrolyte constituting the solid electrolyte layer 17 has an atomic ratio of oxygen (O) atoms to sulfur (S) atoms (O /S ratio) is greater than 0.4 and less than 0.8. Although the O/S ratio in the entire solid electrolyte may be set to a value within this range as in the present embodiment, the O/S ratio in the entire solid electrolyte need not be a value within this range. do not have. In this case, at least part of the surface of the solid electrolyte layer on the side of the negative electrode active material layer has an atomic ratio of oxygen (O) atoms to sulfur (S) atoms (O/S ratio) greater than 0.4 and 0.8. It suffices if there is a region that is less than . The value of the O/S ratio is preferably more than 0.4 and 0.75 or less, more preferably more than 0.4 and 0.7 or less.

Here, according to the studies of the present inventors, it is possible to charge a battery using a sulfide solid electrolyte containing Li, P, S and O and having an O/S ratio of greater than 0.4 for the solid electrolyte layer. A discharge test revealed that the average charge voltage at a constant current density was lower than when a sulfide solid electrolyte having an O/S ratio of 0.4 or less was used. In view of Ohm's law (V=I×R), this means that the resistance in the solid electrolyte (lithium ion diffusion resistance) decreases when the O/S ratio becomes a value greater than 0.4. It is assumed that By providing the region where the diffusion resistance of lithium ions is reduced in this way on the surface of the solid electrolyte layer on the side of the negative electrode active material layer, the contact resistance between these layers is reduced, effectively contributing to the reduction of the internal resistance of the battery. It is considered to be possible.

Similarly, according to the studies of the present inventors, the sulfide solid electrolyte containing Li, P, S and O and having an O/S ratio of less than 0.8 has excellent wettability to metallic lithium. found. As a result of attempting to form a thin film of metallic lithium by vacuum evaporation on the surface of a sulfide solid electrolyte with a varied O/S ratio, it was found that when the O/S ratio was 0.8 or more, the thin film It was found that the formation of By providing the region with improved wettability to metallic lithium in this way on the surface of the solid electrolyte layer on the side of the negative electrode active material layer, the contact resistance between these layers is also reduced, which is effective in reducing the internal resistance of the battery. It is thought that it can contribute.

Here, there is no particular limitation on the method of obtaining a sulfide solid electrolyte containing Li, P, S and O and having an O/S ratio of greater than 0.4 and less than 0.8, and conventional technical common sense It can be taken into consideration as appropriate. One example is a method of adjusting the press treatment conditions for a sulfide solid electrolyte containing Li, P and S (actually, it also inevitably contains oxygen (O)). According to such a method, the value of the O/S ratio in the sulfide solid electrolyte containing Li, P and S (and O) can be controlled. Specific conditions for such press treatment are not particularly limited. 10 to 50° C.) for 0.5 to 15 minutes, preferably 1 to 10 minutes. Here, the pressurizing condition for the press treatment may be about 10 to 500 MPa, preferably 50 to 450 MPa. By subjecting the constituent material of the solid electrolyte layer to such press treatment to form the solid electrolyte layer, the value of the O/S ratio in the entire solid electrolyte layer can be controlled as shown in FIGS. 1 and 2, for example. It is possible to obtain an all-solid-state battery.

On the other hand, when a sulfide solid electrolyte containing Li, P and S (actually, inevitably also containing oxygen (O)) is left in an oxygen-containing atmosphere, the surface of the solid electrolyte is oxidized. and the amount of oxygen (O) near the surface increases. Therefore, the surface of the sulfide solid electrolyte containing Li, P and S (which inevitably also contains oxygen (O)) is polished using sandpaper, a polishing machine, or the like. As a result, the oxide film existing on the surface is removed, and as a result, the amount of oxygen (O) in the vicinity of the surface of the solid electrolyte is reduced, and the O/S ratio in the vicinity of the surface of the sulfide solid electrolyte is reduced. can be made By applying such polishing treatment to the surface of the solid electrolyte layer on the side of the negative electrode active material layer while adjusting the degree of polishing, a region having a desired O/S ratio is polished to the negative electrode active material layer side of the solid electrolyte layer. can be provided on the surface of These treatments may be performed multiple times, or the above-described press treatment and polishing treatment may be performed in combination so that a region having a desired O/S ratio is provided.

The O/S ratio can also be controlled by appropriately selecting the type of jig used when producing the solid electrolyte layer by press treatment. For example, press processing is performed using a sleeve made of SLD steel (manufactured by Hitachi Metals Tool Steel Co., Ltd.) and an SLD steel pin having hard chrome plating on both ends, which is used in the Examples section described later. Thus, it is possible to control the O/S ratio within the predetermined range of the present application. At this time, if the solid electrolyte to be press-treated is similarly press-treated with the SUS foil sandwiched between both ends, it is possible to control the O/S ratio to be small. SLD steel is an alloy steel corresponding to SKD-11 according to JIS, and is also called die steel. This SLD steel is a high carbon steel with a carbon content of 1.4-1.6%, in addition to this, chromium 11-13%, vanadium 0.2-0.5%, molybdenum 0.8-1.2% is the basic composition.

[Positive collector plate and negative collector plate]
The material constituting the current collectors (25, 27) is not particularly limited, and known highly conductive materials conventionally used as current collectors for secondary batteries can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable as the constituent material of the current collector plate. From the viewpoint of light weight, corrosion resistance and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. The same material or different materials may be used for the positive collector plate 25 and the negative collector plate 27 .

[Positive lead and negative lead]
Although not shown, the current collectors (11, 12) and the current collector plates (25, 27) may be electrically connected via a positive lead or a negative lead. Materials used in known lithium-ion secondary batteries can also be employed as the constituent materials of the positive and negative electrode leads. In addition, the parts taken out from the exterior should be heat-shrunk with heat-resistant insulation so that they do not come into contact with peripheral equipment or wiring and cause electric leakage and affect the product (for example, automobile parts, especially electronic equipment, etc.). Covering with a tube or the like is preferred.

[Battery exterior material]
As the battery exterior material, a known metal can case can be used, and as shown in FIGS. 1 and 2, a bag-like case using a laminate film 29 containing aluminum that can cover the power generation element is used. can be The laminate film may be, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order, but is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high power output and cooling performance and can be suitably used for batteries for large equipment for EV and HEV. Moreover, since the group pressure applied to the power generating element from the outside can be easily adjusted, the outer package is more preferably a laminate film containing aluminum.

The stacked battery according to the embodiment shown in FIG. 2 has a structure in which a plurality of single cell layers are connected in parallel, so that it has a high capacity and excellent cycle durability. Therefore, the stacked battery according to this embodiment is suitably used as a power source for driving EVs and HEVs.

Although one embodiment of the all-solid-state battery has been described above, the present invention is not limited to the configuration described in the above-described embodiment, and can be appropriately modified based on the description of the claims. be.

For example, as a type of battery to which the all-solid-state battery according to the present invention is applied, a positive electrode active material layer electrically coupled to one side of the current collector and a positive electrode active material layer electrically coupled to the opposite side of the current collector A bipolar battery including a bipolar electrode having a negative electrode active material layer with a

FIG. 3 schematically shows a bipolar all-solid-state lithium-ion secondary battery (hereinafter also simply referred to as “bipolar secondary battery”), which is an embodiment of the all-solid-state battery according to the present invention. It is a cross-sectional view. A bipolar secondary battery 10b shown in FIG. 3 has a structure in which a substantially rectangular power generation element 21 in which charge/discharge reactions actually progress is sealed inside a laminate film 29 that is a battery exterior body.

As shown in FIG. 3, the power generation element 21 of the bipolar secondary battery 10b of the present embodiment has a positive electrode active material layer 13 electrically coupled to one surface of the current collector 11, and the current collector 11 It has a plurality of bipolar electrodes 23 with a negative electrode active material layer 15 electrically coupled to the opposite surface. Each bipolar electrode 23 is laminated via the solid electrolyte layer 17 to form the power generation element 21 . In addition, the solid electrolyte layer 17 has a structure in which a solid electrolyte is formed into a layer. In addition, the solid electrolyte layer 17 contains Li ₃ PS ₄ which is a kind of sulfide solid electrolyte, and the composition of the Li ₃ PS ₄ constituting the solid electrolyte layer 17 (specifically, O/S ratio) is controlled to the "specific composition" described above. At this time, the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23 face each other with the solid electrolyte layer 17 interposed therebetween. , bipolar electrodes 23 and solid electrolyte layers 17 are alternately stacked. That is, the solid electrolyte layer 17 is sandwiched between the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of the other bipolar electrode 23 adjacent to the one bipolar electrode 23. It is

Adjacent positive electrode active material layer 13 , solid electrolyte layer 17 , and negative electrode active material layer 15 constitute one cell layer 19 . Therefore, it can be said that the bipolar secondary battery 10b has a structure in which the cell layers 19 are stacked. The positive electrode active material layer 13 is formed only on one side of the outermost current collector 11 a on the positive electrode side located in the outermost layer of the power generating element 21 . In addition, the negative electrode active material layer 15 is formed only on one side of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generating element 21 .

Furthermore, in the bipolar secondary battery 10b shown in FIG. 3, a positive electrode current collector plate (positive electrode tab) 25 is arranged adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form the battery exterior. It is led out from the laminate film 29 . On the other hand, a negative electrode current collector plate (negative electrode tab) 27 is arranged adjacent to the outermost layer current collector 11 b on the negative electrode side, and is similarly extended to lead out from the laminate film 29 .

Note that the number of times the cell layers 19 are stacked is adjusted according to the desired voltage. Further, in the bipolar secondary battery 10b, the number of stacking of the cell layers 19 may be reduced if sufficient output can be secured even if the thickness of the battery is made as thin as possible. In the bipolar secondary battery 10b as well, in order to prevent external shocks and environmental deterioration during use, the power generation element 21 is enclosed under reduced pressure in a laminate film 29, which is a battery outer body, and a positive electrode collector plate 25 and a negative electrode collector are enclosed. A structure in which the electric plate 27 is taken out of the laminate film 29 is preferable.

[Assembled battery]
An assembled battery is an object configured by connecting a plurality of batteries. Specifically, at least two or more are used, and serialization or parallelization or both of them are used. By connecting in series and in parallel, it is possible to freely adjust the capacity and voltage.

A plurality of batteries can be connected in series or in parallel to form a small detachable assembled battery. Then, a plurality of these detachable small assembled batteries are further connected in series or in parallel to form a large-capacity, large-capacity battery suitable for a vehicle drive power supply or an auxiliary power supply that requires high volumetric energy density and high volumetric output density. An assembled battery with an output can also be formed. How many batteries are connected to make an assembled battery, and how many stages of small assembled batteries are stacked to make a large-capacity assembled battery, depends on the battery capacity of the vehicle (electric vehicle) in which it is installed. It should be decided according to the output.

[vehicle]
INDUSTRIAL APPLICABILITY The all-solid-state battery according to the present invention maintains discharge capacity even after long-term use, and has good cycle characteristics. Furthermore, it has a high volumetric energy density. Vehicle applications such as electric vehicles, hybrid electric vehicles, fuel cell vehicles, and hybrid fuel cell vehicles require higher capacity, larger size, and longer life compared to electrical and portable electronic equipment applications. . Therefore, the non-aqueous electrolyte secondary battery can be suitably used as a power source for vehicles, for example, a power source for driving a vehicle or an auxiliary power source.

Specifically, a battery or an assembled battery formed by combining a plurality of these batteries can be mounted on a vehicle. In the present invention, it is possible to configure a long-life battery with excellent long-term reliability and output characteristics, so when such a battery is installed, a plug-in hybrid electric vehicle with a long EV driving range and an electric vehicle with a long driving range per charge can be configured. . Batteries or assembled batteries made by combining a plurality of these, for example, in the case of automobiles, hybrid vehicles, fuel cell vehicles, electric vehicles (all four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.) , two-wheeled vehicles (motorcycles) and three-wheeled vehicles) will provide a long-lasting and highly reliable automobile. However, the application is not limited to automobiles, for example, it can be applied to various power sources for other vehicles, such as moving bodies such as trains, and power sources for installation such as uninterruptible power supplies. It can also be used as

[Experimental example 1]
100 mg of a sulfide solid electrolyte (β-Li ₃ PS ₄ ) was weighed, placed in a sleeve made of SLD steel (manufactured by Hitachi Metals Tool Steel Co., Ltd., steel equivalent to SKD-11), and sandwiched between SLD pins plated with hard Cr at both ends. , at room temperature (25°C) and a pressure of 390 MPa for 1 minute to obtain an electrolyte pellet (1) of this experimental example.

[Experimental example 2]
After pressing by the method of Experimental Example 1 described above, the electrolyte pellet (2) of this Experimental Example was obtained by further hot-pressing at 280° C. and a pressure of 90 MPa for 15 minutes.

[Experimental example 3]
After hot pressing by the method of Experimental Example 2 described above, one surface of the pellet was polished using #600 sandpaper to obtain the electrolyte pellet (3) of this Experimental Example. .

[Experimental example 4]
100 mg of a sulfide solid electrolyte (β-Li ₃ PS ₄ ) was weighed, placed in an SLD sleeve, sandwiched between SUS foils at both ends, and sandwiched between hard Cr-plated SLD pins, and 390 MPa at room temperature (25 ° C.). The electrolyte pellet (4) of this experimental example was obtained by pressing for 1 minute at a pressure of .

[Evaluation example]
(Analysis of surface composition of electrolyte pellet by XPS method)
The surface compositions of the electrolyte pellets (1) to (4) obtained in Experimental Examples 1 to 4 were analyzed by X-ray photoelectron spectroscopy (XPS). Also, from the obtained analysis results, the ratio (atomic ratio) of the amount of oxygen (O) atoms to the amount of sulfur (S) atoms was calculated. The results are shown in Table 1 below. Among the surface compositions shown in Table 1, the value of the electrolyte pellet (3) obtained in Experimental Example 3 is the composition of the polished surface.

(Formation of metal thin film by vacuum deposition method)
Au An attempt was made to form two metal thin films, a thin film (thickness of 30 nm) and a Li thin film (thickness of 1 μm). As a result, these metal thin films could be formed on the surfaces of electrolyte pellet (1), electrolyte pellet (3) and electrolyte pellet (4), but these metal thin films were formed on the surface of electrolyte pellet (2). could not be formed. This is probably because the surface O/S ratio of the electrolyte pellet (2) showed a large value of 0.8 or more, and as a result, the wettability between the surface and the metals (Au and Li) deteriorated. .

(Charging and discharging test; measurement of limiting current density)
An evaluation cell using the electrolyte pellet (1) or the electrolyte pellet (3) as a solid electrolyte layer was produced by the following method, and a charge/discharge test was performed.

The electrolyte pellet was enclosed in a Macor tube (battery protection tube), and a metal lithium foil (thickness: 200 μm) was attached to both sides. Then, a Li symmetrical cell was produced by sandwiching each lithium metal foil with pins made of SKD-11. The confining pressure during cell assembly was set to 0.2 MPa.

Using the Li symmetric cell fabricated in this way, at a measurement temperature of 60 ° C., while changing the current density _by 0.1 mA / _cm in the range of 0.1 to 10 mA / cm A charge/discharge test was performed for each cycle at each current density, with charging and discharging as one cycle. Then, the current density (limiting current density) at which the battery voltage stopped increasing even when the current density was increased was determined. The results are shown in Table 1 below.

As shown in Table 1, in Experimental Example 3 using the electrolyte pellet (3), the limiting current density showed a small value of 0.3 mA/cm ² . This is probably because the O/S ratio on the surface of the electrolyte pellet (3) showed a small value of 0.4 or less, and as a result, the diffusion resistance of lithium ions in the electrolyte pellet increased.

From the above, lithium (Li), phosphorus (P), sulfur (S) and oxygen (O) are contained, and the atomic ratio (O / S ratio) of oxygen (O) atoms to sulfur (S) atoms is 0 By providing the region larger than .4 and less than 0.8 on the surface of the solid electrolyte layer on the side of the negative electrode active material layer, an increase in the contact resistance between the solid electrolyte layer and the negative electrode active material layer is suppressed, and the battery It is expected that it will be possible to prevent an increase in the internal resistance of the

10 all-solid lithium ion secondary battery,
10a, 50 stacked secondary battery,
10b bipolar secondary battery,
11 current collector,
11' positive electrode current collector,
11″ negative electrode current collector,
11a outermost current collector on the positive electrode side,
11b outermost current collector on the negative electrode side,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21, 57 power generation element,
23 bipolar electrodes,
25 positive collector plate (positive tab),
27 negative electrode current collector (negative electrode tab),
29 Laminate film.

Claims (6)

a positive electrode in which a positive electrode active material layer containing a positive electrode active material is arranged on the surface of a positive electrode current collector;
a negative electrode in which a negative electrode active material layer containing a negative electrode active material containing metallic lithium or a lithium-containing alloy is arranged on the surface of a negative electrode current collector;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a sulfide solid electrolyte;
comprising a power generation element having
The solid electrolyte layer contains lithium (Li), phosphorus (P), sulfur (S) and oxygen (O) on at least a part of the surface on the negative electrode active material layer side, and An all-solid-state battery having a region in which the atomic ratio of (O) atoms (O/S ratio) is greater than 0.4 and less than 0.8. 2. The all-solid battery according to claim 1, wherein said solid electrolyte layer has said region over the entire surface on the side of said negative electrode active material layer. When viewed from above, the outer peripheral edge of the solid electrolyte layer coincides with the outer peripheral edge of the positive electrode active material layer, and at least a portion of the outer peripheral edge of the negative electrode active material layer is located inside the outer peripheral edge of the solid electrolyte layer. The all-solid-state battery according to claim 1 or 2. 4. The all-solid-state battery according to claim 1, wherein an outer peripheral edge of said negative electrode active material layer is included in said region when viewed from above. The negative electrode active material layer is
a first active material layer comprising metallic lithium or a lithium-containing alloy;
a second active material layer containing a material that can be alloyed with lithium;
, wherein the second active material layer is arranged between the solid electrolyte layer and the first active material layer. The all-solid-state battery according to any one of claims 1 to 5, which is an all-solid-state lithium ion secondary battery.

Images