JP2023048547A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery with excellent cycle durability.SOLUTION: An all-solid battery comprises: a positive electrode active material layer 15; a negative electrode active material layer 13; a solid electrolyte layer 17 arranged between the positive electrode active material layer 15 and the negative electrode active material layer 13, containing a solid electrolyte; and a structure-maintaining body 18 located over the solid electrolyte layer 17 and the negative electrode active material layer 13. A surface of a portion located at least on the solid electrolyte layer 17, of the structure-maintaining body 18 is formed of an insulating substance.SELECTED DRAWING: Figure 4

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, notebook 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 in widespread use, 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 all-solid-state secondary batteries, in principle, various problems caused by combustible organic electrolytes do not occur unlike conventional liquid-type lithium secondary batteries. 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, since solid electrolytes are generally hard and brittle, there is a problem that it is difficult to obtain a large-sized powder-molded sheet as a solid electrolyte layer. In order to solve such problems, there is known a technique of stably maintaining a solid electrolyte sheet by introducing a woven fabric as a core material of the solid electrolyte sheet. For example, in Patent Document 1, a woven fabric for supporting a solid electrolyte is used as a core material of a solid electrolyte, in which the surface layer of a woven fabric woven with monofilament synthetic fiber yarn is coated with a material containing a polymer. Techniques are disclosed.

JP 2005-005024 A

However, as a result of investigation by the present inventors, it was found that the all-solid-state battery using the technology described in Patent Document 1 may have a problem that the discharge capacity of the battery is significantly reduced by repeating the charge-discharge cycle. found.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an all-solid-state battery that is excellent in cycle durability when charging and discharging cycles are repeated.

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 structure-maintaining member at a position extending over the solid electrolyte layer and 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 disposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte, and A structure-maintaining member positioned over the solid electrolyte layer and the negative electrode active material layer is provided, and at least the surface of the portion of the structure-maintaining member positioned on the solid electrolyte layer is made of an insulating material.

ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state battery excellent in cycle durability at the time of repeating the cycle of charging/discharging 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 schematic view showing an enlarged cross-section of a single cell layer constituting a power generation element of the stacked battery shown in FIGS. 1 and 2. FIG. FIG. 4 is a schematic view of the single cell layer of FIG. 3 as viewed obliquely from above.

One embodiment of the present invention includes a positive electrode active material layer, a negative electrode active material layer, a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte, and A structure-maintaining body positioned over a negative electrode active material layer, wherein the surface of at least a portion of the structure-maintaining body positioned on the solid electrolyte layer is made of an insulating material.

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 type (internal parallel connection type) flat laminated type all-solid secondary battery (hereinafter also simply referred to as a “laminated battery”), which is one form of an all-solid-state battery, will be taken as an example of the present invention. explain. 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, 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 shape, the laminate film 29 may be used as the exterior material, or a conventional cylindrical can (metal can) may be used. Preferably, the power generation element 21 is housed inside a laminate film 29 containing aluminum. Weight reduction can be achieved by this configuration.

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. Moreover, in a winding-type all-solid-state battery, instead of tabs, for example, cylindrical cans (metal cans) may be used to form terminals.

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 ₆ PS ₅ Cl, which is a type of sulfide solid electrolyte. The positive electrode has a structure in which positive electrode active material layers 15 containing a positive electrode active material (here, elemental sulfur (S)) are arranged on both sides of a positive electrode current collector 11″. The negative electrode has a negative electrode current collector 11′. A negative electrode active material layer 13 containing a negative electrode active material (here, metal Li) is arranged on both sides of the positive electrode active material layer 15. Specifically, one positive electrode active material layer 15 and the adjacent negative electrode active material layer 15 The positive electrode, the solid electrolyte layer 17, and the negative electrode are laminated in this order so that the positive electrode, the solid electrolyte layer 17, and the negative electrode face each other with the solid electrolyte layer 17 interposed therebetween. 2 can be said to have a configuration in which a plurality of single cell layers 19 are stacked and electrically connected in parallel. 2 , a structure-maintaining body is provided between all the solid electrolyte layers 17 included in the power generation element 21 and the negative electrode active material layer 13 so as to cover both layers.

A positive collector plate (tab) 27 and a negative collector plate (tab) 25 are attached to the positive electrode current collector 11″ and the negative electrode current collector 11′, respectively. It has a structure in which it is sandwiched between the ends of the laminate film 29, which is the battery exterior material, and led out to the outside of the laminate film 29. The positive electrode current collector plate 27 and the negative electrode current collector plate 25 are provided as necessary. may be attached to the positive electrode current collector 11″ and the negative electrode 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).

FIG. 3 is a schematic view showing an enlarged cross section of the single cell layer 19 that constitutes the power generation element 21 of the stacked battery 10a shown in FIGS. 1 and 2. FIG. Moreover, FIG. 4 is a schematic view of the unit cell layer 19 viewed obliquely from above. Although the negative electrode active material layer 13 and the solid electrolyte layer 17 are shown separated from each other in FIG. 4 for convenience of explanation, they actually have a laminated structure as shown in FIG.

As shown in FIGS. 3 and 4, in the present embodiment, a positive electrode current collector 11″ constituting a cell layer 19, a positive electrode active material layer 15, a solid electrolyte layer 17, and a negative electrode active material layer 13 , and the negative electrode current collector 11′ are stacked in this order, and the structure maintaining body 18 is positioned over two layers, the solid electrolyte layer 17 and the negative electrode active material layer 13, as shown in FIG. More specifically, as shown in FIG. 4, the contact surface between the solid electrolyte layer 17 and the negative electrode active material layer 13 (the area surrounded by the outer peripheral edge of the solid electrolyte layer and the negative electrode The structure-maintaining body 18 is disposed so as to cover most (about 90%) of the region surrounded by the outer peripheral edge of the active material layer. Cracking of the solid electrolyte layer 17 and peeling of the solid electrolyte layer 17 and the negative electrode active material layer 13 due to expansion and contraction of the negative electrode active material layer 13 due to charge/discharge can be prevented by providing it so as to extend over the This improves the cycle durability of the battery.

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, examples of 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 negative electrode active material layer contains a negative electrode active material. Such a negative electrode active material absorbs ions released from the positive electrode during charging, and releases ions during discharging.

The type of negative electrode active material is not particularly limited, but carbon materials, metal oxides, and metal active materials can be mentioned. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, soft carbon, and the like. Moreover, as a metal oxide, _Nb2O5 , _{Li4Ti5O12 etc.} are mentioned _, for _example . Furthermore, a silicon-based negative electrode active material or a tin-based negative electrode active material may be used. Here, it is preferable to use simple Si as the silicon-based negative electrode active material. Similarly, it is also preferable to use a silicon oxide such as SiO _x (0.3≦x≦1.6) disproportionated into two phases of Si phase and silicon oxide phase. At this time, the range of x is more preferably 0.5≦x≦1.5, and more preferably 0.7≦x≦1.2. Furthermore, an alloy containing silicon (silicon-containing alloy-based negative electrode active material) may be used. On the other hand, examples of negative electrode active materials containing a tin element (tin-based negative electrode active materials) include Sn alone, tin alloys (Cu—Sn alloys, Co—Sn alloys), amorphous tin oxides, tin silicon oxides, and the like. Among these, SnB _0.4 P _0.6 O _3.1 is exemplified as an amorphous tin oxide. SnSiO ₃ is exemplified as tin silicon oxide. A metal containing lithium may also be used as the negative electrode active material. Such a negative electrode active material is not particularly limited as long as it is an active material containing lithium, and examples thereof include metallic lithium and lithium-containing alloys. Lithium-containing alloys include, for example, alloys of Li and at least one of In, Al, Si and Sn. 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. The present invention exhibits particularly excellent effects when the expansion and contraction of the negative electrode active material during charging and discharging are large. Thus, from the viewpoint of large expansion and contraction and high capacity, the negative electrode active material contained in the negative electrode active material layer is at least one selected from the group consisting of metallic lithium, graphite, and silicon-based negative electrode active materials. It is preferably contained, more preferably at least one selected from the group consisting of metallic lithium, graphite and a silicon-based negative electrode active material, and particularly preferably metallic lithium.

The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but when the negative electrode active material is graphite, a silicon-based negative electrode active material, or the like, it is, for example, within the range of 40 to 99% by mass. more preferably in the range of 50 to 90% by mass.

The negative electrode active material layer preferably further contains 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 -} LiI, _Li2SP2S5 - _Li2O , _{Li2SP 2S5} - _Li2O -LiI, Li2S _- SiS2, Li2S- _SiS2 -LiBr, _{Li2S - SiS2 -} LiCl, _{Li2S - SiS2} - _{B2S3 -} LiI, Li _2S —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 , Ge, Zn, or 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 is a positive number, and M is any one of P, Si, Ge, B, Al, Ga, and 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 contained in the active material layer is preferably a sulfide solid electrolyte containing the element P, and the sulfide solid electrolyte is a material containing Li ₂ SP ₂ S ₅ as a main component. It is more preferable to have Furthermore, the sulfide solid electrolyte may contain halogens (F, Cl, Br, I). In one preferred embodiment, the sulfide solid electrolyte comprises _Li6PS5X , where X is Cl, Br or I, preferably _Cl .

When the sulfide solid electrolyte is Li ₂ SP 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. 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 1 to 60% by mass, more preferably in the range of 10 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 the solid electrolyte described above.

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

[Solid electrolyte layer]
In the secondary battery according to the present embodiment, the solid electrolyte layer is a layer interposed between the positive electrode active material layer and the negative electrode active material layer and essentially containing a solid electrolyte.

The specific form of the solid electrolyte contained in the solid electrolyte layer is not particularly limited, and the solid electrolytes exemplified in the column of the negative electrode active material layer and their preferred forms can be similarly employed. In some cases, solid electrolytes other than the solid electrolytes described above may be used together. However, the ratio of the content of the sulfide solid electrolyte to 100% by mass of the total amount of the solid electrolyte is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more. , more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

The solid electrolyte layer may further contain a binder in addition to the solid electrolyte described above.

The thickness of the solid electrolyte layer varies depending on the configuration of the intended all-solid secondary 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. , and more preferably 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 10 μm or more.

[Positive electrode active material layer]
In the secondary battery according to this embodiment, the positive electrode active material layer contains a sulfur-containing positive electrode active material. The type of the positive electrode active material containing sulfur is not particularly limited, but examples thereof include elemental sulfur (S) and particles or thin films of organic sulfur compounds or inorganic sulfur compounds. Any material may be used as long as it can release ions at times and store ions at the time of discharge. 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 preferable. 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, elemental sulfur (S), Li ₂ S, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , MoS ₂ , MoS ₃ and the like. Among them, S, Li ₂ S, S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , FeS ₂ and MoS ₂ are preferred, and elemental sulfur (S), Li ₂ S, TiS ₂ and FeS ₂ are more preferred, Elementary sulfur (S) or Li ₂ S is particularly preferable from the viewpoint of high capacity. As the elemental sulfur (S), α-sulfur, β-sulfur, or γ-sulfur having an _S8 structure may be used. These simple elements of sulfur (S) occlude ions and exist in the positive electrode active material layer in the form of sulfides during discharge.

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 section on the negative electrode active material layer can be similarly employed. Furthermore, the positive electrode active material layer may further contain a conductive aid and/or a binder.

[Structural maintenance body]
The all-solid-state battery according to this embodiment is characterized in that a structure-maintaining body is provided across the solid electrolyte layer and the negative electrode active material layer. That is, at least one structure-maintaining body is arranged in a state of being embedded in both the solid electrolyte layer and the negative electrode active material layer. By arranging the structure maintainers in this way, the cycle durability of the all-solid-state battery can be improved.

Although the details of the reason why this effect is produced are unknown, the following mechanism is conceivable. The decrease in capacity due to repeated charge-discharge cycles in conventional all-solid-state batteries is due to repeated expansion and contraction of the negative electrode active material layer due to charge and discharge, which causes cracking of the solid electrolyte layer, and the separation of the solid electrolyte layer and the negative electrode active material layer. can be caused by deviation in the contact surface of On the other hand, according to the all-solid-state battery according to the present embodiment, the structure maintainer is provided over the solid electrolyte layer and the negative electrode active material layer. By arranging the structure-maintaining member in the solid electrolyte layer, the structure of the solid electrolyte layer is maintained, and cracking of the solid electrolyte layer due to expansion of the negative electrode active material layer can be suppressed. Further, by arranging the structure maintainer over the solid electrolyte layer and the negative electrode active material layer, the surface of the solid electrolyte layer facing the negative electrode active material layer and the surface of the negative electrode active material layer facing the solid electrolyte layer contact can be maintained with In particular, when the negative electrode active material layer is metallic lithium (when the negative electrode is a so-called lithium deposition type in which metallic lithium is deposited on the negative electrode current collector in the charging process), the structure maintainer is present. As a result, metallic lithium can be deposited more uniformly in the planar direction of the negative electrode (thickness of the deposited metallic lithium becomes more uniform in the planar direction) as compared with the case where the structure-maintaining body is not provided. As a result, even if the expansion and contraction of the negative electrode active material layer are repeated, the separation at the contact surface can be suppressed.

At least the surface of the structure-maintaining body located on the solid electrolyte layer is made of an insulating material. Since the surface of the portion located in the solid electrolyte layer is made of an insulating material, it is possible to prevent the all-solid-state battery from short-circuiting and the potential decomposition of the solid electrolyte. The insulating substance is not particularly limited as long as it has insulating properties, but is preferably a non-conductive thermoplastic resin. As non-conductive thermoplastic resins, various substances such as polyolefins such as polypropylene (PP) and polyethylene (PE), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) are used. be able to. Among them, polypropylene, polyethylene, and polyvinylidene fluoride are preferable, and polypropylene and polyethylene are more preferable from the viewpoint of having high potential resistance.

The structure-maintaining body of the present embodiment preferably has a metal skeleton. In this case, the insulating material may cover at least the surface of the skeleton that is located in the solid electrolyte layer. It is preferable that The metal used for the skeleton of the structure-maintaining body is preferably a metal having a Vickers hardness of 90 or more, specifically at least one selected from the group consisting of copper, stainless steel, nickel, titanium and aluminum. is preferred. By using these metals for the skeleton, the strength of the structure-maintaining body becomes sufficient, and distortion of the solid electrolyte layer caused by expansion and contraction of the negative electrode active material layer can be suppressed.

The shape of the structure maintaining body of the present embodiment is not particularly limited, and a mesh shape (including a two-dimensional mesh structure and a three-dimensional mesh shape), a block shape, a hook shape, a needle shape, and the like can be used as appropriate. , preferably in a mesh shape. Specific examples of the mesh shape include punching metal shapes and expanded metal shapes. Since the structure-maintaining body has a mesh shape, a good contact state between the solid electrolyte layer and the negative electrode active material layer is maintained when charging and discharging are repeated. In particular, when the negative electrode active material layer is metallic lithium (when the negative electrode is a so-called lithium deposition type in which metallic lithium is deposited on the negative electrode current collector in the charging process), the mesh-shaped structure maintaining body Metallic lithium is deposited in the voids of the At this time, although the detailed reason is unknown, the thickness of the metallic lithium deposited in each gap can become more uniform compared to the case where the structure maintaining body is not provided. Therefore, a more uniform metallic lithium layer is formed in the surface direction of the negative electrode, and a good contact state between the solid electrolyte layer and the negative electrode active material layer is maintained. As a result, the cycle durability of the all-solid-state battery can be further improved.

From the viewpoint of improving the strength of the solid electrolyte layer, the lower limit of the thickness of the structure maintainer is preferably 5 μm or more, more preferably 10 μm or more, and particularly preferably 15 μm or more. On the other hand, the upper limit of the thickness of the structure maintainer is preferably 100 μm or less, more preferably 50 μm or less, and more preferably 25 μm or less, from the viewpoint of improving the volume energy density of the battery. .

As shown in FIG. 3, the structure maintainer of the present embodiment is positioned over the solid electrolyte layer and the negative electrode active material layer. It is preferable that the proportion of the solid electrolyte layer is higher than that of the solid electrolyte layer. In the case where a plurality of structure maintainers are arranged, the ratio of the number of structure maintainers of the above configuration is preferably 50% or more, more preferably 75% or more, and still more preferably 90% or more. Yes, particularly preferably 100%. Positioning the structure-maintaining body in this manner can further increase the strength of the solid electrolyte layer. In addition, in this specification, the said ratio is obtained by the measuring method using the scanning electron microscope (SEM) described in the column of an Example.

The structure maintainer of the present embodiment is arranged so as to cover part or all of the contact surface between the solid electrolyte layer and the negative electrode active material layer. That is, when the power generating element is viewed in plan, the overlapping portion (1) between the area (a) surrounded by the outer peripheral edge of the solid electrolyte layer and the area (b) surrounded by the outer peripheral edge of the negative electrode active material layer A part or the whole overlaps with the area (c) surrounded by the outer peripheral edge of the structure maintainer. At this time, the overlapping portion between the overlapping portion (1) and the area (c) surrounded by the outer peripheral edge of the structure maintaining member is defined as an overlapping portion (2). In addition, when a plurality of structure maintenance bodies are arranged, the smallest area among the areas enclosed so as to include all of the plurality of structure maintenance bodies is defined as the "area surrounded by the outer peripheral edge of the structure maintenance bodies ( c)”. Here, the ratio of the area of the overlapping portion (2) to the area of the overlapping portion (1) is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. , 100%. The area (c) surrounded by the outer peripheral edge of the structure maintaining body may be larger than the area of the overlapping portion (1). However, from the viewpoint of improving the volume energy density of the battery, the ratio of the area (c) to the area of the overlapping portion (1) is preferably 100% or more and 120% or less, and is 100% or more and 110% or less. is more preferably 100% or more and 105% or less. By arranging the structure-maintaining bodies in this way, it is possible to more effectively prevent separation between the solid electrolyte layer and the negative electrode active material layer.

[Method for manufacturing all-solid-state battery]
The all-solid secondary battery according to this embodiment can be produced, for example, according to the following production method. First, a solid electrolyte layer is temporarily formed by pressing a solid electrolyte powder material. Next, these materials are arranged in the order of the solid electrolyte layer, the positive electrode active material, and the positive electrode current collector on one surface of the temporarily molded solid electrolyte layer. Then, by pressurizing these, a laminate composed of the solid electrolyte layer, the positive electrode active material layer, and the positive electrode current collector is temporarily formed. Subsequently, the structure-maintaining body, the negative electrode active material, and the negative electrode current collector are arranged in this order from the solid electrolyte layer on the side of the solid electrolyte layer on which the positive electrode active material layer and the positive electrode current collector do not exist in the laminate. . Then, by pressurizing these, the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the structure maintaining body, the negative electrode active material layer, and the negative electrode current collector (the structure maintaining body is the solid electrolyte layer and the negative electrode active material layer). An all-solid-state battery is obtained having a single cell layer consisting of a single cell layer arranged so as to be positioned over the entire surface.

[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 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 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 configured, 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 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

The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited only to the following examples. In the following, the instruments and devices used in the glove box were thoroughly dried in advance.

《Creation of structural maintenance body》
Polyethylene (PE) powder was melted at 130° C. using a heat press and pressed into an expanded metal made of stainless steel (SUS) (minor diameter: 0.7 mm, major diameter: 1.3 mm, thickness: 20 μm). After the press-fitting, the material was further heated at 130° C. to partially dissolve the PE, thereby producing a PE-coated SUS structure-maintaining body (1).

By the same method, a polypropylene (PP)-coated SUS structure-maintaining body (2) and a polyvinylidene fluoride (PVDF)-coated SUS structure-maintaining body (3) were also produced.

Using expanded metals made of copper (Cu), nickel (Ni), and titanium (Ti) having the same shape as the above-mentioned expanded metal made of SUS and coated with PP according to the method described above, a Cu structure-maintaining body ( 4) A PVDF-coated Cu structure-maintaining body (5), a PVDF-coated Ni-made structural-maintaining body (6), and a PVDF-coated Ti structural-maintaining body (7) were prepared.

<<Fabrication of all-solid secondary battery>>
All-solid secondary batteries of Examples 1 to 7 and Comparative Examples 1 and 2 were produced in a glove box of an argon atmosphere with a dew point of −68° C. or less by the following method.

(Adjustment of sulfur-impregnated porous conductor)
Add 1.20 g of sulfur (manufactured by Aldrich) to 0.200 g of a porous conductor (Ketjenblack, manufactured by Lion Corporation) in an argon atmosphere glove box with a dew point of −68° C. or less, and thoroughly with an agate mortar. After mixing, the mixed powder was placed in a sealed pressure-resistant autoclave container and heated at 170° C. for 3 hours to melt sulfur and impregnate the porous conductor with sulfur to obtain a sulfur-impregnated porous conductor.

(Preparation of sulfur-containing positive electrode mixture)
In an argon atmosphere glove box with a dew point of −68° C. or less, 40 g of zirconia balls with a diameter of 5 mm, 0.130 g of a sulfur-impregnated porous conductor, and 0.070 g of a solid electrolyte (Li ₆ PS ₅ Cl, manufactured by Ampcera). The powder was placed in a zirconia container with a capacity of 45 ml and treated with a planetary ball mill (Premium line P-7 manufactured by Fritsch) at 370 rpm for 6 hours to obtain a sulfur-containing positive electrode mixture powder. The composition of the sulfur mixture was sulfur:solid electrolyte:carbon=50:40:10.

(Example 1)
A SUS cylindrical convex punch (10 mm diameter) was inserted into one side of a Macor cylindrical tube jig (inner diameter 10 mm, outer diameter 23 mm, height 20 mm), and a sulfide solid electrolyte ( 80 mg of Li ₆ PS ₅ Cl (manufactured by Ampcera) was added. After that, another SUS cylindrical convex punch was inserted to sandwich the solid electrolyte, and a solid electrolyte layer with a diameter of 10 mm and a thickness of 20 μm was formed into a cylindrical tube jig by pressing for 3 minutes at a pressure of 75 MPa using a hydraulic press. formed inside.

Next, the cylindrical convex punch inserted from the upper side is once extracted, 7.5 mg of the sulfur-containing positive electrode mixture prepared above is put on one side of the solid electrolyte layer in the cylindrical tube, and the cylindrical convex punch ( A positive electrode current collector) was inserted and pressed at a pressure of 100 MPa for 3 minutes to form a positive electrode active material layer 15 having a diameter of 10 mm and a thickness of about 0.06 mm on one side of the solid electrolyte layer.

Next, the lower cylindrical convex punch (which also serves as a negative electrode current collector) is extracted, and a lithium foil (manufactured by Nilaco Corporation, thickness 0.20 mm) punched to a diameter of 8 mm as a negative electrode is placed on the lithium foil as a structure maintainer. The PE-coated SUS structure-maintaining body (1) is placed, and the SUS structure-maintaining body (1) is placed on the solid electrolyte layer side from the bottom of the cylindrical tube jig. By inserting a punch and pressing for 3 minutes at a pressure of 300 MPa, a negative electrode current collector (punch), a lithium negative electrode, a PE-coated SUS structural maintenance body (1), a solid electrolyte layer, a positive electrode active material layer 15, and a positive electrode. An all-solid secondary battery was produced in which current collectors (punches) were stacked in this order.

(Example 2)
An all-solid secondary battery was produced in the same manner as in Example 1, except that the SUS structure-maintaining body (2) coated with PVDF was used as the structure-maintaining body.

(Example 3)
An all-solid secondary battery was produced in the same manner as in Example 1, except that a PP-coated SUS structure-maintaining body (3) was used as the structure-maintaining body.

(Example 4)
An all-solid secondary battery was produced in the same manner as in Example 1, except that a Cu structure-maintaining body (4) coated with PP was used as the structure-maintaining body.

(Example 5)
An all-solid secondary battery was produced in the same manner as in Example 1, except that the Cu structure-maintaining body (5) coated with PVDF was used as the structure-maintaining body.

(Example 6)
An all-solid secondary battery was produced in the same manner as in Example 1, except that the Ni structure-maintaining body (6) coated with PVDF was used as the structure-maintaining body.

(Example 7)
An all-solid secondary battery was produced in the same manner as in Example 1, except that a Ti structure-maintaining body (7) coated with PVDF was used as the structure-maintaining body.

(Comparative example 1)
An all-solid secondary battery was produced in the same manner as in Example 1, except that the structure-maintaining body was not included.

(Comparative example 2)
An all-solid secondary battery was produced in the same manner as in Example 1, except that an uncoated SUS structure-maintaining body was used as the structure-maintaining body.

<<Observation of cross section of all-solid secondary battery>>
When the cross section of the all-solid secondary battery of Examples 1 to 7 described above was observed using a scanning electron microscope (SEM), it was found that the thickness of the structure maintaining body in the stacking direction was located in the negative electrode active material layer. It was confirmed that the proportion located in the solid electrolyte layer was higher than the proportion.

<<Evaluation example of discharge capacity retention rate>>
Using an electrochemical diagnostic device (BioLogic, VSP-300), in a constant temperature bath set at 25° C., the discharge capacity retention rate of the all-solid secondary battery produced above was evaluated by the following method.

The battery was fully charged at 25° C. with a 0.05C-3.1V constant current and constant voltage charge under the condition of a cutoff current of 0.01C, and then discharged at a cutoff voltage of 1.1V to 0.05C. Then, the 50th cycle discharge capacity retention rate [%] was calculated as a percentage of the discharge capacity at the 50th cycle to the discharge capacity at the first cycle. The results are shown in Table 1 below.

In Comparative Example 1 containing no structure-maintaining body and Comparative Example 2 in which the surface of the structure-maintaining body was not coated with an insulating substance, a failure occurred during the process of repeating charging and discharging, and the battery did not reach the 50th cycle. On the other hand, Examples 1 to 7, which were coated with an insulating material, reached the 50th cycle, and therefore showed sufficient improvement in cycle durability compared to Comparative Examples. In particular, Examples 1 to 3, in which SUS was used as the skeleton of the structure-maintaining body, exhibited particularly excellent discharge capacity retention.

10a laminated battery,
11' negative electrode current collector,
11″ cathode current collector,
13 negative electrode active material layer,
15 positive electrode active material layer,
17 solid electrolyte layer,
18 structure maintenance body 19 cell layer,
21 power generation element,
25 negative electrode current collector,
27 positive current collector,
29 Laminate film.

Claims (7)

positive electrode active material layer,
negative electrode active material layer,
a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer and containing a solid electrolyte; and a structure maintainer positioned over the solid electrolyte layer and the negative electrode active material layer,
An all-solid-state battery, wherein a surface of at least a portion of the structure-maintaining member located on the solid electrolyte layer is made of an insulating material. The all-solid-state battery according to claim 1, wherein the structure-maintaining body has a metal skeleton. 3. The all solid state battery according to claim 2, wherein said metal is at least one selected from the group consisting of copper, stainless steel, nickel, titanium and aluminum. The all-solid-state battery according to any one of claims 1 to 3, wherein said insulating substance is at least one selected from the group consisting of polypropylene and polyethylene. The all-solid-state battery according to any one of claims 1 to 4, wherein said structure maintainer has a mesh shape. The all-solid according to any one of claims 1 to 5, wherein a ratio of the thickness in the stacking direction of the structure maintaining body that is located in the solid electrolyte layer is higher than a ratio that is located in the negative electrode active material layer. battery. The all-solid-state battery according to any one of claims 1 to 6, wherein the negative electrode active material layer contains at least one selected from the group consisting of metallic lithium, graphite, and silicon-based negative electrode active materials.

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