JP2023119151A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery in which short-circuiting at an outer peripheral end portion is suppressed.SOLUTION: An all-solid battery is provided, comprising: a positive electrode active material layer 15; a negative electrode active material layer 13; a solid electrolyte layer 17 interposed between the positive electrode active material layer 15 and the negative electrode active material layer 13, and including a solid electrolyte; a carbon-containing layer 12 arranged between the negative electrode active material layer 13 and the solid electrolyte layer 17, and including carbon material; and a metal portion 14 which is provided at an outer peripheral edge portion of the negative electrode active material layer and can be alloyed with lithium.SELECTED DRAWING: Figure 7

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 as compared with consumer lithium secondary batteries used in mobile phones, laptop computers, and the like. Therefore, lithium secondary batteries, which have the highest theoretical energy among all practical batteries, have attracted attention and are being rapidly developed.

Lithium secondary batteries, which are currently widely used, use a combustible organic electrolyte as an electrolyte. Such a liquid-type lithium 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 secondary batteries using oxide-based or sulfide-based solid electrolytes have been actively conducted. A solid electrolyte is a material composed mainly of an ionic conductor capable of conducting ions in a solid. Therefore, in the all-solid secondary battery, in principle, various problems due to the combustible organic electrolyte, unlike the conventional liquid-type lithium secondary battery, do not occur. In general, the use of high-potential, large-capacity positive electrode materials and large-capacity negative electrode materials can significantly improve the output density and energy density of the battery.

However, the all-solid secondary battery has a problem that dendrites deposited in the battery grow during repeated charging and discharging, and this causes a short circuit due to communication between the positive electrode and the negative electrode. To address this problem, a layer containing carbon is provided between the solid electrolyte layer and the negative electrode active material layer of the all-solid secondary battery to suppress the deposition and growth of dendrites, thereby suppressing the short circuit. A technique is known (for example, Patent Document 1).

U.S. Patent Application Publication No. 2019/0157723

However, as a result of investigation by the present inventors, the all-solid-state battery provided with a layer containing carbon between the solid electrolyte layer and the negative electrode active material layer as described above has an edge short circuit at the outer peripheral edge of the all-solid-state battery. was found not to be adequately suppressed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an all-solid-state battery in which edge short-circuiting at the outer peripheral edge is suppressed.

The present inventors have made intensive studies to solve the above problems. As a result, the present inventors have found that the above problems can be solved by providing a metal portion that can be alloyed with lithium in the outer peripheral portion of the negative electrode active material layer in an all-solid-state battery, and have completed the present invention.

An all-solid-state battery according to one embodiment of the present invention includes a positive electrode active material layer, a negative electrode active material layer, a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte, A carbon-containing layer containing a carbon material, which is arranged between the negative electrode active material layer and the solid electrolyte layer, and a metal portion which is provided at the outer peripheral edge of the negative electrode active material layer and which can be alloyed with lithium. Prepare.

ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state battery which suppressed the edge short circuit in the outer peripheral edge part can be provided.

FIG. 1 is a perspective view showing the appearance of a stacked battery according to one embodiment of the present invention. FIG. 2 is a cross-sectional view along line 2-2 shown in FIG. FIG. 3 is a graph showing charge/discharge curves of the test cell A. FIG. 4 is a cross-sectional view of the test cell B. FIG. FIG. 5 is a graph showing charge/discharge curves of the test cell B. FIG. FIG. 6 is a plan view of a layer composed of a negative electrode active material layer and a metal portion. FIG. 7 is a schematic view showing an enlarged cross-section of a single cell layer that constitutes a power generating element of the stacked battery shown in FIGS. 1 and 2. FIG.

One embodiment of the present invention includes a positive electrode active material layer, a negative electrode active material layer, a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte, a negative electrode active material layer and The all-solid-state battery includes a carbon-containing layer containing a carbon material disposed between solid electrolyte layers, and a metal portion provided on the outer peripheral edge portion of the negative electrode active material layer and capable of being alloyed with lithium.

Hereinafter, the above-described embodiments of the present invention 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 only 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. In the following, a non-bipolar (internal parallel connection type) flat laminated all-solid secondary battery (hereinafter also simply referred to as “laminated battery” or “all-solid battery”), which is one form of all-solid-state battery, will be described. The present invention will be explained by way of example. As described above, the solid electrolyte that constitutes the all-solid secondary battery is a material that is mainly composed of an ionic conductor capable of conducting ions in a solid state. Therefore, in the all-solid secondary battery, there is an advantage that, in principle, various problems due to the combustible organic electrolyte, unlike conventional liquid-type lithium secondary batteries, do not occur. In general, the use of high-potential, high-capacity positive electrode materials and high-capacity negative electrode materials also has the advantage that the power density and energy density of the battery can be greatly improved.

FIG. 1 is a perspective view showing the appearance of a stacked battery according to one embodiment of 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.

As shown in FIG. 1, the laminated battery 10a has a rectangular flat shape, and from both sides thereof, a positive collector plate 27 and a negative collector plate 25 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, there are no particular restrictions on how the collector plates (27, 25) shown in FIG. 1 can be taken out. The positive current collecting plate 27 and the negative current collecting plate 25 may be pulled out from the same side, or the positive current collecting plate 27 and the negative current collecting plate 25 may be divided into a plurality of pieces and pulled out from each side. It is not limited to what is shown in FIG. 1, such as good.

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 configuration in which a positive electrode, a solid electrolyte layer 17, a carbon-containing layer 12, and a negative electrode are laminated. The positive electrode has a structure in which positive electrode active material layers 15 containing a positive electrode active material are arranged on both sides of a positive electrode current collector 11″. The negative electrode contains a negative electrode active material on both sides of a negative electrode current collector 11′. It has a structure in which an active material layer 13 is arranged, and a metal portion 14 is provided at the outer peripheral portion of the negative electrode active material layer 13 so as to surround the entire circumference of the negative electrode active material layer 13 .

More specifically, the single cell layer 19 that constitutes the stacked battery 10a shown in FIG. 17 and the carbon-containing layer 12 are laminated so as to face each other. That is, the single cell layer 19 includes the positive electrode current collector 11″, the positive electrode active material layer 15, the solid electrolyte layer 17, the carbon-containing layer 12, the negative electrode active material layer 13, and the metal part 14, and the negative electrode current collector 11. ' are laminated in this order.Therefore, it can be said that the laminated battery 10a shown in FIG.

A positive electrode current collector (tab) 27 and a negative electrode current collector (tab) 25 are attached to the positive electrode current collector 11″ and the negative electrode current collector 11′, respectively. , and is led out of the laminate film 29 so as to be sandwiched between the ends of the laminate film 29, which is a battery exterior material. Accordingly, they may be attached to the positive current collector 11″ and the negative current collector 11′ of each electrode by ultrasonic welding, resistance welding, or the like, via a positive electrode lead and a negative electrode lead (not shown).

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

[Current collector]
The current collector has a function of mediating transfer of electrons from the 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.

Moreover, as the resin having conductivity, a resin obtained by adding a conductive filler to a non-conductive polymer material can be used.

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. Furthermore, if the negative electrode active material layer and the positive electrode active material layer to be described later themselves have conductivity and can exhibit a current collecting function, a current collector is used as a member separate from these electrode active material layers. No need. In such a form, the negative electrode active material layer to be described later constitutes the negative electrode as it is, and the positive electrode active material layer to be described later constitutes the positive electrode as it is.

[Negative electrode active material layer]
The all-solid-state battery according to this embodiment is a so-called lithium deposition type battery in which lithium metal is deposited on the negative electrode current collector during the charging process. In this case, the layer composed of lithium metal deposited on the negative electrode current collector during the charging process becomes the negative electrode active material layer. Therefore, the thickness of the negative electrode active material layer increases as the charging process progresses, and the thickness of the negative electrode active material layer decreases as the discharging process progresses. Although the negative electrode active material layer does not have to exist at the time of complete discharge, depending on the situation, a certain amount of the negative electrode active material layer made of lithium metal may be arranged at the time of complete discharge.

The thickness of the negative electrode active material layer at the time of full charge varies depending on the configuration of the intended all-solid-state battery, but is preferably in the range of 0.1 to 1000 μm, for example.

[Solid electrolyte layer]
The solid electrolyte layer is a layer containing a solid electrolyte as a main component and interposed between the negative electrode active material layer and the positive electrode active material layer. The solid electrolyte is not particularly limited, but includes, for example, a sulfide solid electrolyte and an oxide solid electrolyte. From the viewpoint of high ionic conductivity, the solid electrolyte preferably contains a sulfide solid electrolyte.

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 -} LiI, _Li2SP2S5 - _Li2O , _{Li2SP 2S5} - _Li2O -LiI, Li2SP2S5-LiCl _{, Li2SP2S5 - LiBr , Li2S - SiS2} , _{Li2S - SiS2 -} LiI, _Li2 S—SiS ₂ —LiBr, Li ₂ S—SiS ₂ —LiCl, Li ₂ S—SiS ₂ —B ₂ S ₃ —LiI, Li ₂ S—SiS ₂ —P ₂ S ₅ —LiI, Li ₂ S—B ₂ S ₃ , Li ₂ SP ₂ S ₅ -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 P, Si, Ge, B, Al, Ga or In). 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 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. Examples of the binder include, but are not limited to, 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 copolymers and their hydrogenated products, thermoplastic polymers such as styrene/isoprene/styrene block copolymers and their hydrogenated products, tetrafluoroethylene/hexafluoropropylene copolymers (FEP), tetrafluoroethylene・Perfluoroalkyl vinyl ether copolymer (PFA), ethylene/tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene/chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride ( PVF) and other fluororesins, vinylidene fluoride-hexafluoropropylene fluororubbers (VDF-HFP fluororubbers), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluororubbers (VDF-HFP-TFE fluororubbers) , vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluororubber (VDF-PFP-TFE fluororubber), vinylidene fluoride-per Vinylidene fluoride fluororubber such as fluoromethyl vinyl ether-tetrafluoroethylene fluororubber (VDF-PFMVE-TFE fluororubber), vinylidene fluoride-chlorotrifluoroethylene fluororubber (VDF-CTFE fluororubber), epoxy resin, carboxymethyl cellulose, and the like. Among them, polyimide, styrene-butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

The thickness of the solid electrolyte layer varies depending on the configuration of the target all-solid-state battery, but from the viewpoint of improving the volume energy density of the battery, it is preferably 600 μm or less, more preferably 500 μm or less, More preferably, it is 400 μm or less. On the other hand, the lower limit of the thickness of the solid electrolyte layer is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more.

[Positive electrode active material layer]
The positive electrode active material layer contains a positive electrode active material. The type of positive electrode active material is not particularly limited, but 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 and LiNi _{0 Spinel} -type active materials such as _.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. Among them, composite oxides containing lithium and nickel are preferably used, and more preferably Li(Ni--Mn--Co) O ₂ and those in which a part of these transition metals are replaced with other elements (hereinafter , also simply referred to as “NMC composite oxide”) is used. The NMC composite oxide has a layered crystal structure in which a lithium atomic layer and a transition metal (Mn, Ni and Co are arranged in an orderly manner) atomic layer are alternately stacked via an oxygen atomic layer. It contains one Li atom, and the amount of Li that can be extracted is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, and a high capacity can be obtained.

NMC composite oxides also include composite oxides in which a portion of the transition metal element is replaced with another metal element, as described above. Other elements in that case include Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, and Cu. , Ag, Zn, etc., preferably Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, more preferably Ti, Zr, P, Al, Mg, Cr, more preferably Ti, Zr, Al, Mg, or Cr from the viewpoint of improving cycle characteristics.

Furthermore, it is also one of preferred embodiments that a sulfur-based positive electrode active material is used. Examples of the sulfur-based positive electrode active material include particles or thin films of organic sulfur compounds or inorganic sulfur compounds, which can release lithium ions during charging and absorb lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur. Any substance that can Examples of organic sulfur compounds include disulfide compounds, sulfur-modified polyacrylonitrile represented by compounds described in WO 2010/044437, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), polysulfide carbon, and the like. Among them, disulfide compounds, sulfur-modified polyacrylonitrile, and rubeanic acid are preferred, and sulfur-modified polyacrylonitrile is particularly preferred. As the disulfide compound, those having a dithiobiurea derivative, a thiourea group, a thioisocyanate group, or a thioamide group are more preferred. Here, sulfur-modified polyacrylonitrile is sulfur-atom-containing modified polyacrylonitrile obtained by mixing sulfur powder and polyacrylonitrile and heating the mixture under an inert gas or under reduced pressure. Its putative structure is described, for example, in Chem. Mater. 2011, 23, 5024-5028, polyacrylonitrile is ring-closed to form a polycyclic structure, and at least part of S is bonded to C. The compound described in this document has strong peak signals near 1330 cm ^-1 and 1560 cm ^-1 in the Raman spectrum, and further peaks near 307 cm ^-1 , 379 cm ^-1 , 472 cm ^-1 and 929 cm ^-1 . do. On the other hand, inorganic sulfur compounds are preferable because of their excellent stability. Specifically, sulfur (S), S-carbon composites, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , Li ₂ S, MoS ₂ , MoS ₃ and the like. Among them, S, S-carbon composites, TiS ₂ , TiS ₃ , TiS ₄ , FeS ₂ and MoS ₂ are preferred, and S-carbon composites, TiS ₂ and FeS ₂ are more preferred. Here, the S-carbon composite includes a sulfur powder and a carbon material, and is in a composite state by subjecting them to heat treatment or mechanical mixing. More specifically, the state in which sulfur is distributed on the surface and in the pores of the carbon material, the state in which sulfur and the carbon material are uniformly dispersed at the nano level and are aggregated into particles, and the state in which fine sulfur It is a state in which the carbon material is distributed on the surface or inside the powder, or a state in which a plurality of these states are combined.

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. However, the ratio of the content of the sulfur-containing positive electrode active material to 100% by mass of the total amount of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass. more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

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 also preferably contains a solid electrolyte, and more preferably the solid electrolyte contains a sulfide solid electrolyte. As for the specific form and preferred form of the solid electrolyte such as the sulfide solid electrolyte, those described in the above section of the solid electrolyte layer can be similarly employed.

The positive electrode active material layer may further contain at least one of a conductive aid and a binder in addition to the positive electrode active material and the solid electrolyte. As the binder, those described in the section of the solid electrolyte layer can be appropriately used.

The conductive aid is not particularly limited, but for example, metals such as aluminum, stainless steel (SUS), silver, gold, copper, titanium, alloys or metal oxides containing these metals; carbon fiber (specifically, Vapor grown carbon fiber (VGCF), polyacrylonitrile carbon fiber, pitch carbon fiber, rayon carbon fiber, activated carbon fiber, etc.), carbon nanotubes (CNT), carbon black (specifically, acetylene black, Ketjen black (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 positive electrode active material layer contains a conductive aid, the content of the conductive aid in the positive electrode active material layer is not particularly limited, but is preferably 0 to 10% by mass with respect to the total weight of the positive electrode active material layer. , more preferably 2 to 8% by mass, more preferably 4 to 7% by mass. Within such a range, it is possible to form a stronger electron conduction path in the positive electrode active material layer, which can effectively contribute to the improvement of battery characteristics.

The thickness of the positive electrode active material layer varies depending on the configuration of the intended all-solid-state battery, but for example, it is preferably in the range of 0.1 to 1000 μm, more preferably 40 to 100 μm.

[Carbon-containing layer]
The all-solid-state battery according to this embodiment has a carbon-containing layer that is arranged between the negative electrode active material layer and the solid electrolyte layer and contains a carbon material. Precipitation and growth of dendrites can be suppressed by having the carbon-containing layer in the all-solid-state battery.

The carbon material is not particularly limited, but carbon black (specifically, acetylene black, Ketjenblack (registered trademark), furnace black, channel black, thermal lamp black, etc.), carbon nanotubes (CNT), graphite, hard carbon etc. Of these, carbon black is preferred, and at least one selected from the group consisting of acetylene black, Ketjenblack (registered trademark), furnace black, channel black and thermal lamp black is more preferred.

The content of the carbon material in the carbon-containing layer is not particularly limited, but is preferably in the range of 50 to 100% by mass, more preferably in the range of 70 to 100% by mass, and 90 to 100% by mass. is more preferably within the range of , particularly preferably 95 to 100% by mass.

The carbon-containing layer may consist of only a carbon material as long as a self-supporting film can be produced only from the carbon material, and may contain a binder as necessary. Since the specific form of the binder contained in the carbon-containing layer is the same as described above, detailed description is omitted here.

Although the content of the binder in the carbon-containing layer is not particularly limited, it is preferably in the range of 1 to 10% by mass, more preferably in the range of 2 to 5% by mass. If the content of the binder is 1% by mass or more, a carbon-containing layer having sufficient strength can be formed. If the content of the binder is 10% by mass or less, a decrease in energy density can be suppressed.

The carbon-containing layer preferably does not contain components other than the carbon material and the binder. Therefore, according to a preferred embodiment, the carbon-containing layer consists of only the carbon material, or consists of the carbon material and the binder.

Although the thickness of the carbon-containing layer is not particularly limited, it is preferably in the range of 1 to 50 μm, more preferably in the range of 5 to 40 μm, even more preferably in the range of 10 to 30 μm. . When the thickness of the carbon-containing layer is 1 μm or more, the precipitation and growth of dendrites can be further suppressed. When the thickness of the carbon-containing layer is 50 μm or less, it is possible to suppress a decrease in energy density.

The outer peripheral edge of the carbon-containing layer is positioned so as to overlap with the outer peripheral edge of the solid electrolyte layer, or is positioned inside the outer peripheral edge of the solid electrolyte layer when the all-solid-state battery according to the present embodiment is viewed in plan. is preferably located in In addition, when the all-solid-state battery according to the present embodiment is viewed from above, the outer peripheral edge of the carbon-containing layer is positioned so as to overlap with the outer peripheral edge of the metal part, or is positioned closer to the outer peripheral edge of the metal part than the outer peripheral edge of the metal part. It is preferably located on the outside. Having the outer edges of the carbon-containing layer at these locations can increase the energy density of the all-solid-state battery.

[Metal part]
The all-solid-state battery according to this embodiment has a metal part that is provided on the outer peripheral edge of the negative electrode active material layer and that can be alloyed with lithium. By arranging the metal parts in this way, it is possible to prevent end short circuits in the all-solid-state battery. Moreover, it is preferable that the metal portion is provided over the entire circumference of the outer peripheral portion of the negative electrode active material layer as in the present embodiment. As a result, dendrites can be prevented from being generated over the entire periphery of the outer peripheral edge of the negative electrode active material layer.

From the results of Experiments 1 and 2 below, the present inventors have found that arranging the metal part on the outer peripheral edge of the negative electrode active material layer can suppress end short circuits in an all-solid-state battery.

<Experiment 1>
<<Preparation of test cell A>>
First, as the test cell A, a lithium symmetrical cell was produced. More specifically, under an inert atmosphere, a positive electrode current collector (SUS foil), metallic lithium, a solid electrolyte layer (Li ₆ PS ₅ Cl), a carbon-containing layer (prepared using furnace black), metallic lithium, Negative electrode current collectors (SUS foil) were laminated in this order. Then, it was sandwiched between the positive electrode current collector (made of SUS) and the negative electrode current collector (made of SUS), and sealed in a pressurized container capable of blocking the outside air while applying a restraining pressure of 20 MPa. was made.

《Charging and discharging test》
Next, the test cell A was subjected to a charge/discharge test by the following method. In addition, the measurement was performed in a constant temperature constant temperature bath set at 25°C. The charging/discharging conditions are as follows.
[Voltage range] -2.0 to 2.0V
[Charging process] 0.2 mA/cm ²
[Discharge process] 0.2 mA/cm ²
[Terminal conditions] Current capacity 6.0 mAh/cm ² .

FIG. 3 is a graph showing charge/discharge curves of the test cell A. FIG. When charging was performed as the first operation, as shown in FIG. 3, charging and subsequent discharging could be performed. It was found that when discharging was performed as the first operation, as shown in FIG. 3, the overvoltage increased and the battery did not function.

From the results of Experiment 1, in an all-solid-state battery having a carbon-containing layer on the negative electrode side, lithium released from the positive electrode active material during the initial charge is occluded by the carbon material in the carbon-containing layer. It turns out that a function expresses.

<Experiment 2>
<<Preparation of test cell B>>
Next, a lithium/indium asymmetric cell (22 in FIG. 4) was produced as a test cell B. More specifically, as shown in FIG. 4, a positive electrode current collector 11″ (SUS foil), a lithium metal foil layer 15′, a solid electrolyte layer 17, a carbon-containing layer 12 (made using furnace black), An indium (In) foil 14' and a negative electrode current collector 11' (SUS foil) were laminated in this order, and sandwiched between the positive electrode current collector (made of SUS) and the negative electrode current collector (made of SUS). A test cell B was prepared by encapsulating in a pressurized container that can be shut off under a confining pressure of 20 MPa.

《Charging and discharging test》
Next, the test cell B was subjected to a charge/discharge test by the following method. In addition, the measurement was performed in a constant temperature constant temperature bath set at 25°C. The charging/discharging conditions are as follows.
In this test, charging was performed as the first operation, and then discharging was performed.
[Voltage range] -2.0 to 2.0V
[Charging process] 0.2 mA/cm ²
[Discharge process] 0.2 mA/cm ²
[Terminal conditions] Current capacity 8.0 mAh/cm ²

<<Evaluation result of test cell B>>
FIG. 5 is a graph showing charge/discharge curves of the test cell B. FIG. As shown in FIG. 5, the charging as the first operation proceeded without any problem, but when the discharging operation was performed after the rest of 30 minutes, the discharging could not be performed. Considering the results of Experiment 1 described above, this means that although lithium is occluded by the carbon material contained in the carbon-containing layer during charging, the movement of lithium from the negative electrode side is hindered for some reason during discharging. do. Comparing the configurations on the negative electrode side of Experiments 1 and 2 described above, in Experiment 1, the carbon-containing layer and metallic lithium are adjacent to each other, while in Experiment 2, the carbon-containing layer and indium are adjacent to each other. They are different in that respect.

In Experiment 2, the present inventors found that the lithium absorbed by the carbon material during charging moved to indium adjacent to the carbon-containing layer and was alloyed, so that the carbon-containing layer lost its lithium conductivity ( It is speculated that the carbon-containing layer was deactivated) and the test cell B became incapable of discharging. The reason why the carbon-containing layer loses lithium conductivity is that the state in which lithium is alloyed with the metal portion has a higher potential than the state in which lithium is occluded in the carbon-containing layer, and is energetically stable. As a result, the lithium ions once occluded in the carbon-containing layer move from the carbon-containing layer to the more energetically stable metal portion, so that the carbon-containing layer loses lithium conductivity (the carbon-containing layer is deactivated). ).

From these results, by disposing lithium metal as the negative electrode active material layer and providing a metal portion such as indium that can be alloyed with lithium in the outer peripheral portion of the negative electrode active material layer of the all-solid-state battery, lithium metal The carbon-containing layer in the portion adjacent to the metal portion loses the lithium conductivity (deactivated) while maintaining the lithium conductivity that allows charging and discharging. ). As a result, charging and discharging of the outer peripheral end portion of the all-solid-state battery are not performed, thereby preventing the generation of dendrites that cause a short circuit and suppressing the end-short circuit in the all-solid-state battery.

A substance that can be used for the metal part is not particularly limited as long as it can be alloyed with lithium. However, from the viewpoint that the potential in the alloyed state is higher and more stable than in the case where lithium is present alone, and is easily alloyed, the substances that can be used for the metal portion include indium (In), tin (Sn), It is preferably selected from the group consisting of zinc (Zn), aluminum (Al), silicon (Si), silver (Ag), gold (Au) and platinum (Pt). In addition, it can be used for the metal portion from the viewpoint that lithium can be efficiently extracted from the carbon-containing layer because the potential in the alloyed state is higher than that in the state where lithium is occluded in the carbon-containing layer. More preferably, the material is selected from the group consisting of indium (In), tin (Sn), aluminum (Al), and silicon (Si), with indium being particularly preferred.

In this specification, the term “peripheral edge of the negative electrode active material layer” refers to the negative electrode active material layer located outside the outer peripheral edge of the negative electrode active material layer when the all-solid-state battery according to the present embodiment is viewed in plan. It means the peripheral area of the material layer. Preferably, the "peripheral edge of the negative electrode active material layer" is outside the outer peripheral edge of the negative electrode active material layer and the outer peripheral edge of the carbon-containing layer when the all-solid-state battery according to the present embodiment is viewed from above. It may be a region inside the portion. More specifically, when the negative electrode active material layer is rectangular in plan view, as shown in FIG. It has a shape (frame shape). Here, the inner peripheral end portion of the metal portion 14 is in contact with the outer peripheral end portion of the negative electrode active material layer 13 over the entire circumference of the negative electrode active material layer 13 . The width W of the metal portion 14 is preferably more than 0 mm and 50 mm or less, more preferably 1 mm or more and 25 mm or less, and even more preferably 2 mm or more and 10 mm or less.

When the all-solid-state battery according to the present embodiment is viewed in plan, the metal part has an inner peripheral edge located outside the outer peripheral edge of the positive electrode active material layer, and an outer peripheral edge of the metal part is located outside the outer peripheral edge of the positive electrode active material layer. , preferably located within the outer peripheral edge of the solid electrolyte layer. Here, the expression that the outer peripheral end portion of the metal portion is positioned within the outer peripheral end portion of the solid electrolyte layer means that when the all-solid-state battery according to the present embodiment is viewed from above, the outer peripheral end portion of the metal portion is positioned within the outer peripheral end portion of the solid electrolyte layer. It means that it exists at a position overlapping with the edge, or that the outer peripheral edge of the metal part is located inside the outer peripheral edge of the solid electrolyte layer. In particular, when the all-solid-state battery according to the present embodiment is viewed from above, it is more preferable that the outer peripheral end portion of the metal portion be located inside the outer peripheral end portion of the solid electrolyte layer.

FIG. 7 is a schematic view showing an enlarged cross section of the single cell layer 19 that constitutes the power generating element 21 of the stacked battery 10a shown in FIGS. In FIG. 7, the inner peripheral edge of the metal portion (indicated by a dotted line in FIG. 7; 14a) is located outside the outer peripheral edge of the positive electrode active material layer 15, and the outer peripheral edge of the metal portion 14 ( 14b) shown in dashed lines is located inside the outer peripheral edge of the solid electrolyte layer 17, a schematic view of an embodiment of the cell layer 19 is shown. Moreover, as shown in FIG. 7 , the metal portion 14 is arranged so that at least a portion of the metal portion 14 is in contact with the carbon-containing layer 12 .

Since the inner peripheral edge of the metal part is located outside the outer peripheral edge of the positive electrode active material layer, the region not related to charging and discharging where the carbon-containing layer loses lithium conductivity overlaps with the positive electrode active material layer. disappears. As a result, the positive electrode active material in the positive electrode active material layer can be efficiently used for charge-discharge reactions, and the energy density of the all-solid-state battery increases. In addition, since the outer peripheral edge of the metal part is positioned within the outer peripheral edge of the solid electrolyte layer, the extra metal part can be reduced, so that the energy density of the all-solid-state battery can be further increased.

The thickness of the metal part is preferably equal to or less than the thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio (C _An /C _ca ). Here, the "thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio" can be calculated by the following method.

First ^{, the} AC ratio is a _ratio ( _{C An} /C _ca ). The AC ratio is generally designed to be 1 or more. When the AC ratio is 1 or less, part of the capacity of the positive electrode active material layer is left unused for charging and discharging. Since the positive electrode active material is generally expensive, in order to use the positive electrode active material without waste, the AC ratio should be 1 or more, that is, the electrode capacity basis weight of the negative electrode active material layer should be equal to the electrode capacity of the positive electrode active material layer. It is generally designed to be the same as or greater than the basis weight. Here, the "negative electrode surplus capacity of the negative electrode active material layer" based on the AC ratio is a value obtained by multiplying the difference between the AC ratio and 1 by _Cca , which is obtained from the following formula (1).

Next, this negative electrode surplus capacity (mAh/cm ² ) is calculated by dividing the theoretical capacity per mass of the material used for the negative electrode active material (mAh/g; for example, 3862 mAh/g in the case of lithium) and the density (g/cm ³ ; for example, 0.534 g/cm ³ for lithium) and divided by the product (theoretical capacity per volume (mAh/cm ³ )). Thus, the thickness (cm) of the negative electrode surplus capacity is calculated from the surplus capacity of the negative electrode active material layer.

The reason why the thickness of the metal portion is preferably thinner than the thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio is considered to be due to the following mechanism.

In general, the negative electrode active material layer (especially when the negative electrode active material is lithium metal or lithium-containing alloy) expands upon charging and contracts upon discharging. Therefore, in the all-solid-state battery, surface pressure is applied in the stacking direction to prevent the negative electrode active material layer from separating from the stack including the positive electrode active material layer and the solid electrolyte layer. Here, when the thickness of the metal part is greater than the thickness calculated from the excess capacity of the negative electrode active material layer based on the AC ratio, the thickness of the negative electrode active material layer when completely discharged (that is, the thickness of the negative electrode active material is the thinnest) It is considered that the thickness of the metal part becomes thicker than in the state where it is flat), and it becomes an obstacle when the surface pressure is applied to the negative electrode active material layer. Conversely, if the thickness of the metal part is thinner than the thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio, it does not hinder the application of surface pressure to the negative electrode active material layer. It is considered that sufficient pressure can be applied to the negative electrode active material layer, and the negative electrode active material layer can be sufficiently adhered to the laminate. In other words, it can be said that the thickness of the metal part is preferably thinner than the thickness of the negative electrode active material layer, which is the thinnest when completely discharged.

As described above, the thickness of the metal portion is preferably thinner than the thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio. More specifically, the upper limit of the thickness of the metal portion is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 50 μm or less. On the other hand, the lower limit of the thickness of the metal portion is not particularly limited as long as it has a capacity capable of alloying the lithium ions contained in the carbon-containing layer in the region in contact with the metal portion. Specifically, the lower limit of the thickness of the metal portion is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

The above AC ratio is preferably 1 to 2, more preferably 1 to 1.5, still more preferably 1 to 1.2, from the viewpoint of improving energy density and reducing costs.

[Positive collector plate and negative collector plate]
The material constituting the current collector 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 electrode current collector plate and the negative electrode current collector plate.

[Positive lead and negative lead]
Although not shown, the current collector and the current collector plate 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 containing aluminum that can cover the power generation element is used. sell.

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

For example, in the all-solid secondary battery according to the present embodiment, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolytic solution). The amount of the liquid electrolyte (electrolyte solution) that can be contained in the solid electrolyte layer is not particularly limited, but the amount is such that the shape of the solid electrolyte layer formed by the solid electrolyte is maintained and the liquid electrolyte (electrolyte solution) does not leak. is preferably the amount of

[Assembled battery]
An assembled battery is 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 becomes 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. It is also possible to form assembled batteries (battery modules, battery packs, etc.) with output. 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]
A battery or an assembled battery formed by combining a plurality of these batteries can be mounted on a vehicle. In the present invention, since a long-life battery with excellent long-term reliability can be constructed, a plug-in hybrid electric vehicle with a long EV driving range and an electric vehicle with a long driving distance per charge can be constructed by mounting such a battery. 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

10a laminated battery,
11' negative electrode current collector,
11″ cathode current collector,
12 carbon-containing layer,
13 negative electrode active material layer,
14 metal part,
14' indium foil,
15 positive electrode active material layer,
15' lithium metal foil layer,
17 solid electrolyte layer,
19 cell layer,
21 power generation element,
22 test cell B,
25 negative electrode current collector,
27 positive current collector,
29 Laminate film.

Claims (5)

a positive electrode active material layer;
a negative electrode active material layer;
a solid electrolyte layer interposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte;
a carbon-containing layer disposed between the negative electrode active material layer and the solid electrolyte layer and containing a carbon material;
An all-solid-state battery, comprising: a metal part that is provided on the outer peripheral edge of the negative electrode active material layer and that can be alloyed with lithium. When viewed from above, the inner peripheral end of the metal portion is located outside the outer peripheral end of the positive electrode active material layer, and the outer peripheral end of the metal portion is within the outer peripheral end of the solid electrolyte layer. The all-solid-state battery according to claim 1, located at . The all-solid-state battery according to claim 1 or 2, wherein the thickness of the metal portion is equal to or less than the thickness calculated from the surplus capacity of the negative electrode active material layer based on the AC ratio (C _An /C _ca ). The all-solid-state battery according to any one of claims 1 to 3, wherein the negative electrode active material contained in the negative electrode active material layer is lithium metal. The all-solid-state battery according to any one of claims 1 to 4, wherein the metal part contains at least one selected from the group consisting of indium, tin, zinc, aluminum, silicon, silver, gold, and platinum. .