JP7433004B2 - all solid state battery - Google Patents

Description

The present invention relates to an all-solid-state battery.

BACKGROUND ART Conventionally, all-solid-state batteries are known that include a solid electrolyte layer between a positive electrode and a negative electrode. Furthermore, various proposals have been made regarding methods of manufacturing such all-solid-state batteries.

For example, in Patent Document 1, a step of forming a first laminate by pressure-bonding a solid electrolyte layer to a positive electrode layer, and a step of forming a second laminate by pressure-bonding a solid electrolyte layer to a negative electrode layer. Disclosed is a method for manufacturing an all-solid-state battery, further comprising a step of integrating a first laminate and a second laminate by facing the solid electrolyte layers of each and bonding them under pressure. ing.

According to such a manufacturing method, by pressurizing and bonding a positive electrode layer and a negative electrode layer to two solid electrolyte layers in a soft state, the gap between the positive electrode layer and the solid electrolyte layer and between the negative electrode layer and the solid Since a dense interface with no gaps between the electrolyte layers can be obtained, an all-solid-state battery with further reduced interfacial resistance can be manufactured.

Japanese Patent Application Publication No. 2015-118870

On the other hand, in the process of pressurizing and bonding the first laminate and the second laminate, since the opposing solid electrolyte layers are solid, appropriate steps must be taken in order to securely bond them and obtain a gap-free interface. It is necessary to apply high pressure. However, when the first laminate and the second laminate are pressurized at high pressure, the active material layer of one pole collapses, especially in the outer periphery, and the collapsed active material layer is transferred to the active material layer of the other pole. This poses a problem as there is a risk of short-circuiting due to contact.

The present invention provides an all-solid-state battery that includes at least two solid electrolyte layers, a solid electrolyte layer on the positive electrode side and a solid electrolyte layer on the negative electrode side, in which the positive electrode and the negative electrode are prevented from shorting when high pressure is applied. The purpose is to provide technology to suppress this.

The all-solid-state battery according to the present invention includes a positive electrode including a positive electrode active material layer, a negative electrode including a negative electrode active material layer, and a solid electrolyte layer interposed between the positive electrode and the negative electrode and composed of at least two layers. at least one cell layer. The outer peripheral edge of the unit cell layer is arranged so that the outer peripheral edge of the solid electrolyte layer is located at the outermost side from the solid electrolyte layer toward at least one of the end in the stacking direction of the positive electrode and the end in the stacking direction of the negative electrode. It has a steep slope.

According to the present invention, the solid electrolyte layer located at the outermost periphery can prevent the material constituting the collapsed active material layer from moving beyond the solid electrolyte layer from the positive electrode to the negative electrode or from the negative electrode to the positive electrode. Therefore, short circuit between the positive electrode and the negative electrode due to collapse of the active material layer can be suppressed.

FIG. 1 is a cross-sectional view illustrating a single cell layer included in the all-solid-state battery of the first embodiment. FIG. 2 is a diagram illustrating the inclination angle of the inclination formed in the cell layer of the first embodiment. FIG. 3 is a cross-sectional view illustrating a single cell layer included in the all-solid-state battery of the second embodiment. FIG. 4 is a diagram illustrating problems associated with conventional all-solid-state batteries.

[First embodiment]
An all-solid-state battery 10 according to a first embodiment of the present invention will be described.

FIG. 1 is a diagram illustrating a single cell layer 19 included in the all-solid-state battery 10 of the first embodiment. The all-solid-state battery 10 of this embodiment is a so-called laminated type all-solid-state battery in which a power generation element in which a plurality of unit cell layers 19 described below are laminated is sealed with a laminate film which is a battery exterior material. It is a solid state battery. By using a stacked structure, the battery can be made more compact and have a higher capacity. However, the unit cell layer 19 accommodated in the all-solid-state battery 10 to which the present invention is applied does not necessarily have to be a plurality of layers, and may be a single layer. Further, the appearance and internal electrical connection state (electrode structure) of the all-solid-state battery 10 of this embodiment are not particularly limited. The appearance of the all-solid-state battery 10 may be, for example, a rectangular flat corner shape, a circle, or an ellipse shape. Alternatively, it may be of a cylindrical type in which a single layer or a plurality of single cell layers 19 are wound and housed. Further, the electrode structure of the all-solid-state battery 10 may be either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). That is, aspects of the all-solid-state battery 10 other than the configuration of the unit cell layer 19 described below are not particularly limited, regardless of whether they are publicly known or not.

FIG. 1 is a schematic cross-sectional view of a portion of the unit cell layer 19 of this embodiment including the outer peripheral end. The unit cell layer 19 includes a positive electrode current collector 11, a negative electrode current collector 12, a positive electrode active material layer 13, a negative electrode active material layer 14, a positive electrode solid electrolyte layer 15, and a negative electrode solid electrolyte layer 16. It consists of:

More specifically, the unit cell layer 19 includes a positive electrode having a structure in which a positive electrode active material layer 13 containing a positive electrode active material is disposed on the surface of the positive electrode current collector 11, and a negative electrode on the surface of the negative electrode current collector 12. A negative electrode having a structure in which a negative electrode active material layer 14 containing an active material is disposed, and further a solid electrolyte layer composed of two layers between the positive electrode and the negative electrode, that is, a solid electrolyte layer on the positive electrode side. 15 (positive electrode side solid electrolyte layer 15) and a negative electrode side solid electrolyte layer 16 (negative electrode side solid electrolyte layer 16). Details of each component of the all-solid-state battery 10 will be described later.

Here, the problem solved by the all-solid-state battery 10 of this embodiment will be explained with reference to FIG. 4, which shows the structure of a conventional all-solid-state battery. Note that the wording indicating the vertical direction used in the following description is an expression that matches the vertical direction in the figure, and is not necessarily intended to match the vertical direction in the actual direction of gravity.

FIG. 4 is a cross-sectional view of a portion of a conventional all-solid-state battery including the outer peripheral edge of a single cell layer. The unit cell layer is configured, for example, in the shape of a rectangular sheet before being accommodated in the battery exterior material, and the illustrated cross-sectional view is a cross-sectional view that includes one side forming the outer periphery of the rectangle. The all-solid-state battery shown here is an example of an all-solid-state battery manufactured by the conventional manufacturing method described above (see Patent Document 1). That is, the illustrated unit cell layer has two solid electrolyte layers between the positive electrode and the negative electrode, a solid electrolyte layer on the positive electrode side and a solid electrolyte layer on the negative electrode side, and these opposing solid electrolyte layers are pressurized. They are integrated and configured by being joined. When joining these opposing solid electrolyte layers under pressure, the directions of the arrows shown in the figure sandwich the cell layers from above and below, that is, from above to below the positive electrode, and from below to above the negative electrode. A strong external force (pressure) is applied that pinches the cell layer from above and below.

More specifically, in the illustrated unit cell layer, in order to reliably bond the solid electrolyte layer on the positive electrode side and the solid electrolyte layer on the negative electrode side, these opposing solid electrolyte layers are added from the outside of each of the positive electrode side and the negative electrode side. A strong external force is applied toward the bonding surface (interface) of the layers. At this time, the stress caused by the applied external force causes the outer periphery (edge) of the single cell layer to collapse, and the collapsed active material layer (for example, the positive electrode active material layer) is replaced by the opposing active material layer (for example, the negative electrode active material layer). There is a risk that the positive electrode and the negative electrode may come into contact with each other (see arrow A). Furthermore, if a stronger external force is applied, the solid electrolyte layer may collapse, and the active material layer may penetrate the solid electrolyte layer and reach the other active material layer, causing a short circuit (see arrow B).

In this way, an all-solid-state battery having at least two solid electrolyte layers formed by pressure-joining opposing solid electrolyte layers is fastened with a restraint jig during or after pressure-joining. Even after manufacturing the all-solid-state battery, strong pressure may be applied to the unit cell layer, especially in the direction from the top and bottom toward the center, for example, when the pressure increases due to a rise in temperature. At that time, in the single cell layer included in the conventional all-solid-state battery, there is a risk that the positive electrode and the negative electrode may be short-circuited due to the active material layer collapsing particularly at the edge portion due to the applied pressure. The all-solid-state battery 10 of this embodiment has a configuration that suppresses occurrence of such a short circuit. Hereinafter, the details of the configuration of the all-solid-state battery 10 will be continued with reference to FIG. 1.

As shown in FIG. 1, the unit cell layer 19 included in the all-solid-state battery 10 of this embodiment extends from the edge of the positive electrode side solid electrolyte layer 15 in the vertical direction ( An inclination toward the end in the stacking direction, that is, the upper end of the positive electrode current collector 11, and an inclination from the end of the negative electrode side solid electrolyte layer 16 toward an end in the stacking direction of the negative electrode, that is, the lower end of the negative electrode current collector 12. has. The slope formed at the edge portion of the unit cell layer 19 increases from the solid electrolyte layers 15 and 16 on the positive electrode side and the negative electrode side toward the end in the stacking direction of the positive electrode and negative electrode, and the area of each structure in plan view increases. is formed so that it becomes small. In other words, the single cell layer 19 included in the all-solid-state battery 10 extends from the outer circumferential edge of the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 to the edge portion in the stacking direction on the positive electrode side and the negative electrode side. The positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 have an inclination such that the outer peripheral ends of the positive electrode solid electrolyte layer 15 and the negative electrode solid electrolyte layer 16 are located at the outermost side toward the end in the stacking direction.

As a result, in the same way as described with reference to FIG. Even if the active material layer of at least one pole collapses, the provision of the above-mentioned slope makes it difficult for the material constituting the collapsed active material layer to reach the active material layer of the other pole. . In other words, the edge portion of the unit cell layer 19 is provided with the above-described slope, so that the end portion of the solid electrolyte layer located at the outermost periphery plays a role like a wall and constitutes a collapsed active material layer. Since the material is prevented from moving beyond the solid electrolyte layer from the positive electrode to the negative electrode or from the negative electrode to the positive electrode, it is possible to suppress a short circuit between the positive electrode and the negative electrode due to collapse of the active material layer.

Next, the angle of inclination (angle of inclination) provided at the edge portion of the unit cell layer 19 will be explained.

FIG. 2 is a diagram illustrating the inclination angle α of the inclination provided in the cell layer 19 of this embodiment. 2(a) shows a cross-sectional view of the unit cell layer 19 similar to FIG. 1, and FIG. 2(b) shows a partially enlarged view of the portion surrounded by a dotted rectangular frame in FIG. 2(a). In addition, in FIG. 2(b), only the positive electrode active material layer 13 and the positive electrode side solid electrolyte layer 15 are shown for explanation, and the configuration of the negative electrode side is omitted. However, the configuration on the negative electrode side is also similar to the configuration described below with reference to FIG. 2(b).

Incidentally, as shown in FIG. 2(b), the inclination angle α is set at the end of the positive electrode solid electrolyte layer 15 in a direction perpendicular to the surface direction of the positive electrode solid electrolyte layer 15 (in the stacking direction). This is the angle between the perpendicular line and the slope formed at the end of the cell layer 19.

As the inclination angle α becomes larger, the gap (clearance) between the positive electrode active material layer 13 at the edge portion of the unit cell layer 19 becomes larger. When the clearance of the positive electrode active material layer 13 increases, the area where one electrode is absent from the other electrode increases, resulting in deterioration of charging and discharging efficiency. Therefore, from the viewpoint of suppressing deterioration of charge/discharge efficiency, it is preferable that an upper limit is set for the inclination angle α.

The inclination angle α in this embodiment is set so as to satisfy the following formula (1), where t1 is the length of the positive electrode side solid electrolyte layer 15 in the thickness direction (stacking direction).

In addition, in the above formula (1), when the thickness t1 of the positive electrode side solid electrolyte layer 15 is, for example, 100 μm, the clearance (t2 in the figure) of the positive electrode active material layer 13 on the positive electrode side solid electrolyte layer 15 side is 5 mm. It is set as follows. This is set according to the results of evaluating the relationship between the decrease in charge/discharge efficiency and the clearance t2 through experiments and simulations. That is, the above formula (1) is set in accordance with the evaluation result that when the clearance t2 exceeds 5 mm, the charging/discharging efficiency decreases significantly. In this way, by setting the inclination angle α within a range that satisfies the above formula (1), while minimizing the decrease in charging and discharging efficiency, there is a possibility that the positive electrode and the negative electrode may short-circuit due to the applied pressure. It is possible to set an appropriate inclination angle α that can reduce the

The details of the configuration of the unit cell layer 19 included in the all-solid-state battery 10 of this embodiment have been described above. However, the above-mentioned configuration, that is, the slope provided at the edge portion of the unit cell layer 19 does not necessarily need to be provided over the entire outer circumference of the unit cell layer 19. The above-described slope is provided over at least a portion of the edge portion of the unit cell layer 19 . Further, the slope does not necessarily need to be provided on both the positive electrode side and the negative electrode side of the unit cell layer 19, and may be provided on at least one electrode. Further, as shown in FIG. 1, the slope formed in the unit cell layer 19 does not necessarily extend from the edge at the interface between the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 to the upper end of the positive electrode current collector 11. And/or it does not necessarily have to be formed up to the lower end of the negative electrode current collector 12. The slope may be formed, for example, from the end of the positive electrode active material layer 13 side of the positive electrode side solid electrolyte layer 15 to the upper end of the positive electrode active material layer 13 in the stacking direction. That is, the slope may be formed at least at the edge portions of the positive electrode active material layer 13 and/or the negative electrode active material layer 14.

Below, the main constituent members of the unit cell layer 19 that constitutes the all-solid-state battery 10 according to this embodiment will be explained.

[Current collector]
The materials constituting the positive electrode current collector 11 and the negative electrode current collector 12 (hereinafter collectively referred to as current collectors) may be any material that functions as a current collector applicable to all-solid-state batteries in the technical field related to the present invention. There are no particular restrictions. As the constituent material of the current collector, a known material may be used, such as a metal or a resin having conductivity.

[Negative electrode active material layer]
The negative electrode active material layer 14 contains a negative electrode active material. The type of negative electrode active material is not particularly limited, but includes carbon materials, metal oxides, and metal active materials. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Furthermore, examples of metal oxides include Nb ₂ O ₅ and Li ₄ Ti ₅ O ₁₂ . Furthermore, a silicon-based negative electrode active material or a tin-based negative electrode active material may be used. Here, silicon and tin belong to Group 14 elements, and are known to be negative electrode active materials that can greatly improve the capacity of nonaqueous electrolyte secondary batteries. Since these simple substances can absorb and release a large number of charge carriers (lithium ions, etc.) per unit volume (mass), they become high-capacity negative electrode active materials. 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 SiOx (0.3≦x≦1.6) that is disproportionated into two phases, a Si phase and a silicon oxide phase. At this time, the range of x is more preferably 0.5≦x≦1.5, and even more preferably 0.7≦x≦1.2. Furthermore, an alloy containing silicon (silicon-containing alloy negative electrode active material) may be used. On the other hand, examples of negative electrode active materials containing the 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 the amorphous tin oxide. Moreover, SnSiO ₃ is exemplified as the tin silicon oxide. Furthermore, a metal containing lithium (Li) may 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 includes metal lithium and lithium-containing alloys. Examples of lithium-containing alloys include alloys of Li and at least one of In, Al, Si, and Sn. In some cases, two or more types of negative electrode active materials may be used together. Note that it goes without saying that negative electrode active materials other than those mentioned above may be used. Note that, in terms of high capacity, the negative electrode active material preferably contains metallic lithium, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably contains metallic lithium.

Examples of the shape of the negative electrode active material include particulate (spherical, fibrous), thin film, and the like. When the negative electrode active material is in the form of particles, the average particle size (D50) is, for example, preferably within the range of 1 nm to 100 μm, more preferably within the range of 10 nm to 50 μm, and still more preferably 100 nm to 100 μm. It is within the range of 20 μm, particularly preferably within the range of 1 to 20 μm. Note that in this specification, the value of the average particle diameter (D50) of the active material can be measured by a laser diffraction scattering method.

The content of the negative electrode active material in the negative electrode active material layer 14 is not particularly limited, but is preferably in the range of 40 to 99% by mass, and preferably in the range of 50 to 90% by mass, for example. is more preferable.

Preferably, the negative electrode active material layer 14 further includes a solid electrolyte. By including the solid electrolyte in the negative electrode active material layer, the ionic conductivity of the negative electrode active material layer can be improved. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and sulfide solid electrolytes are preferred.

Examples of the sulfide solid electrolyte include LiI-Li ₂ S-SiS ₂ , LiI-Li ₂ S-P2O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ S-P ₂ S ₅ , LiI- Li ₃ PS ₄ , LiI-LiBr-Li ₃ PS ₄ , Li ₃ PS ₄ , Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI, Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ OLiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ 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 S-P ₂ S ₅ -Z _m S _n (However, _m and _n are positive numbers, and Z is either 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 positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In), and the like. Note that the description “Li ₂ S—P ₂ S ₅ ” means a sulfide solid electrolyte made 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 the sulfide solid electrolyte 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 the sulfide solid electrolyte having a Li ₄ P ₂ S ₇ skeleton include a Li--P--S solid electrolyte (eg, Li ₇ P ₃ S ₁₁ ) called LPS. Further, as the sulfide solid electrolyte, for example, LGPS represented by Li _(4-x) Ge _(1-x) P _x S ₄ ( _x satisfies 0<x<1) or the like may be used. Among these, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing the element P, and more preferably the sulfide solid electrolyte is a material containing Li ₂ SP ₂ S ₅ as a main component. Furthermore, the sulfide solid electrolyte may contain halogen (F, Cl, Br, I).

In addition, when the sulfide solid electrolyte is Li2S-P2S5 system, the ratio of Li ₂ S and P ₂ S ₅ is within the range of Li ₂ S:P ₂ S ₅ =50:50 to 100:0 in terms of molar ratio. It is preferable that Li ₂ S:P ₂ S ₅ =70:30 to 80:20.

Further, the sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid phase method. Note that sulfide glass can be obtained, for example, by performing mechanical milling (ball mill, etc.) on a raw material composition. Further, 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 (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25° C.) is preferably 1×10 ⁻⁵ S/cm or more, for example, 1×10 ⁻⁴ S/cm or more. More preferably, it is at least cm. Note that the ionic conductivity value of the solid electrolyte can be measured by an AC impedance method.

Examples of the oxide solid electrolyte include compounds having a NASICON type structure. Examples of compounds having a NASICON type structure include a compound represented by the general formula Li _1+x AlxG _e2-x (PO4) ₃ (0≦x≦2) (LAGP), a compound represented by the general formula Li _{1+x Alx} Ti Examples include a compound (LATP) represented by _2-x (PO4) ₃ (0≦x≦2). Other examples of oxide solid electrolytes include LiLaTiO (e.g., Li _0.3 4La _0.5 1TiO ₃ ), LiPON (e.g., Li _{2 .9} PO _{3 .3} N _0.46 ), LiLaZrO (e.g., Li ₇ La ₃ Zr). ₂ O ₁₂ ), etc.

Examples of the shape of the solid electrolyte include particle shapes such as true spheres and ellipsoids, thin film shapes, and the like. When the solid electrolyte has a particle shape, the average particle diameter (D50) 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 (D50) 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 14 is, for example, preferably in the range of 1 to 60% by mass, more preferably in the range of 10 to 50% by mass. However, when using lithium metal as the negative electrode active material constituting the negative electrode active material layer 14, the content of the solid electrolyte in the negative electrode active material layer 14 is preferably zero. The forms of lithium metal used here include, for example, lithium metal foil, lithium alloy metal foil (alloy types include Mg, Al, In, etc.), and lithium deposited on a base material (the base material is SUS foam). , Al foil, etc.).

In addition to the above-described negative electrode active material and solid electrolyte, the negative electrode active material layer 14 may further contain at least one of a conductive aid and a binder.

Examples of conductive aids include metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium; alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers); (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 to these.

Further, the material employed as the binder is not particularly limited, and any material known in the technical field may be employed as long as it functions as a binder that can be applied to the all-solid-state battery 10.

The thickness of the negative electrode active material layer 14 varies depending on the intended configuration of the all-solid-state battery 10, but is preferably within the range of 0.1 to 1000 μm, for example.

[Cathode active material layer]
It is preferable that the positive electrode active material layer 13 contains a positive electrode active material containing sulfur. The type of positive electrode active material containing sulfur is not particularly limited, but in addition to elemental sulfur (S), particles or thin films of organic sulfur compounds or inorganic sulfur compounds may be used. Any material may be used as long as it can release lithium ions during discharge and occlude lithium ions during discharge. Examples of the organic sulfur compound include disulfide compounds, sulfur-modified polyacrylonitrile represented by the compound described in International Publication No. 2010/044437 pamphlet, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), polysulfide carbon, and the like. Among these, 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, or a thioamide group are more preferable. Here, the sulfur-modified polyacrylonitrile is a modified polyacrylonitrile containing sulfur atoms, which is obtained by mixing sulfur powder and polyacrylonitrile and heating the mixture under an inert gas or reduced pressure. The estimated structure can be found, for example, in Chem. Mater. As shown in 2011, 23, 5024-5028, polyacrylonitrile is ring-closed to become polycyclic, and at least a 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 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, and specifically include elemental sulfur (S), S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , NiS, NiS ₂ , CuS, FeS ₂ , Li Examples include _2S , _MoS2 , _MoS3 , and the like. Among these, S, S-carbon composite, TiS ₂ , TiS ₃ , TiS ₄ , FeS ₂ and MoS ₂ are preferred, elemental sulfur (S), S-carbon composite, TiS ₂ and FeS 2 are more preferred, and elemental sulfur (S), S-carbon composite, TiS 2 and FeS ₂ are more preferred; S) is particularly preferred. Here, the S-carbon composite includes sulfur powder and a carbon material, and is in a composite state by subjecting them to heat treatment or mechanical mixing. In more detail, sulfur is distributed on the surface and within the pores of carbon materials, sulfur and carbon materials are uniformly dispersed at the nano level, and they aggregate to form particles, fine sulfur This is a state in which carbon material is distributed on the surface or inside of the powder, or a state in which a plurality of these states are combined.

The cathode active material layer 13 may include a sulfur-free cathode active material instead of the sulfur-containing cathode active material. Examples of sulfur-free positive electrode active materials include layered rock salt active materials such as LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and Li(Ni-Mn-Co)O2, LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 Examples include spinel type active materials such as O ₄ , olivine type active materials such as LiFePO ₄ and LiMnPO ₄ , and Si-containing active materials such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ . Examples of oxide active materials other than those mentioned above include Li ₄ Ti ₅ O ₁₂ .

In some cases, two or more types of positive electrode active materials may be used together. Note that, of course, positive electrode active materials other than those mentioned above may be used.

Examples of the shape of the positive electrode active material include particulate (spherical, fibrous), thin film, and the like. When the positive electrode active material has a particle shape, the average particle diameter (D50) is, for example, preferably within the range of 1 nm to 100 μm, more preferably within the range of 10 nm to 50 μm, and still more preferably 100 nm to 100 μm. It is within the range of 20 μm, particularly preferably within the range of 1 to 20 μm. Note that in this specification, the value of the average particle diameter (D50) of the active material can be measured by a laser diffraction scattering method.

The content of the positive electrode active material in the positive electrode active material layer 13 is not particularly limited, but is preferably in the range of 40 to 99% by mass, and preferably in the range of 50 to 90% by mass, for example. is more preferable.

Similarly to the negative electrode active material layer 14, the positive electrode active material layer 13 may further contain a conductive additive and/or a binder.

[Solid electrolyte layer]
The positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer (hereinafter also simply referred to as solid electrolyte layers) included in the all-solid-state battery 10 according to the present embodiment contain a solid electrolyte as a main component, and have the above-mentioned This is a layer interposed between the positive electrode active material layer 13 and the negative electrode active material layer 14. Since the specific form of the solid electrolyte contained in the solid electrolyte layer is the same as that described above, detailed explanation will be omitted here.

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

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

The respective thicknesses of the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 vary depending on the configuration of the intended all-solid-state battery 10, but are preferably within the range of 0.1 to 1000 μm, for example, More preferably, it is within the range of 0.1 to 300 μm.

Although not shown, the all-solid-state battery 10 may include a positive current collector plate and a negative current collector plate for extracting power from the one or more cell layers 19 contained therein to the outside of the all-solid-state battery 10. . In this case, the material constituting the current collector plate is not particularly limited, and known highly conductive materials conventionally used as current collector plates for secondary batteries may be used.

Although not shown, the positive electrode current collector 11 and the negative electrode current collector 12 and the positive electrode current collector plate and the negative electrode current collector plate may be electrically connected via a positive electrode lead or a negative electrode lead. As the constituent materials of the positive electrode and negative electrode leads, materials used in known lithium ion secondary batteries may be similarly employed.

As described above, the all-solid-state battery 10 of the first embodiment is composed of at least two layers: a positive electrode including the positive electrode active material layer 13; a negative electrode including the negative electrode active material layer 14; and a negative electrode interposed between the positive electrode and the negative electrode. A solid electrolyte layer (15, 16) is provided, and at least one or more unit cell layer 19 is laminated, and the outer peripheral end of the unit cell layer 19 is an end in the stacking direction of the positive electrode from the solid electrolyte layer (15, 16). The solid electrolyte layer (15, 16) has an inclination such that the outer peripheral end of the solid electrolyte layer (15, 16) is located at the outermost side toward at least one of the ends of the negative electrode in the stacking direction. This allows the ends of the solid electrolyte layers (15, 16) located at the outermost periphery to function as walls even if a strong enough pressure is applied in the direction across the cell layer 19 that the active material layer collapses. However, this prevents the material constituting the collapsed active material layer from moving beyond the solid electrolyte layer from the positive electrode to the negative electrode, or from the negative electrode to the positive electrode, resulting in a short circuit between the positive and negative electrodes due to the active material layer collapsing. can be restrained from doing so.

Further, in the all-solid-state battery 10 of the first embodiment, a perpendicular line drawn perpendicularly to the surface direction of the solid electrolyte layer (15, 16) at the outer peripheral end of the solid electrolyte layer (15, 16) and a line between the unit cell layer 19 Assuming that the angle with the inclined surface formed at the outer peripheral end is α (inclination angle α), the inclination angle α is set so as to satisfy the above formula (1). Thereby, it is possible to set an appropriate inclination angle α that can reduce the risk of short-circuiting between the positive electrode and the negative electrode due to the applied pressure while minimizing the decrease in charging and discharging efficiency.

Further, in the all-solid-state battery 10 of the first embodiment, the negative electrode active material contained in the negative electrode active material layer 14 is composed of a metal containing lithium. Thereby, the capacity of the all-solid-state battery 10 can be increased.

[Second embodiment]
The all-solid-state battery 10 of the second embodiment will be described below. The all-solid-state battery 10 of this embodiment differs from the first embodiment in that the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 have different areas in plan view. Details of the second embodiment will be described below with reference to FIG. 3.

FIG. 3 is a diagram illustrating the unit cell layer 19 included in the all-solid-state battery 10 of the second embodiment. As illustrated, the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 of this embodiment have different areas in plan view. In other words, the unit cell layer 19 of this embodiment is configured such that either the positive electrode side solid electrolyte layer 15 or the negative electrode side solid electrolyte layer 16 is located at the outermost peripheral edge. As a result, even if one of the active material layers collapses due to the applied pressure as described above, the solid electrolyte layer located at the outermost edge will Since it functions more strongly as a wall that prevents movement toward the electrode, it is possible to more effectively prevent the collapsed active material layer from moving beyond the solid electrolyte layer from the positive electrode to the negative electrode, or from the negative electrode to the positive electrode. As a result, short-circuiting between the positive electrode and the negative electrode due to collapse of the active material layer can be more preferably suppressed.

Here, the size relationship in plan view between the positive electrode side solid electrolyte layer 15 and the negative electrode side solid electrolyte layer 16 of this embodiment is based on the material constituting the positive electrode active material layer 13, that is, the positive electrode contained in the positive electrode active material layer 13. It is set as follows depending on the type of active material.

That is, when the positive electrode active material layer 13 is made of a material that does not contain lithium, the area of the positive electrode solid electrolyte layer 15 in plan view is made larger than the area of the negative electrode solid electrolyte layer 16 in plan view. Set. An example of a material that does not contain lithium is a positive electrode active material that contains sulfur. The type of cathode active material containing sulfur is not particularly limited, but may include elemental sulfur (S), particles of organic sulfur compounds or inorganic sulfur compounds, and the details of the cathode active material layer are as described above. .

Here, when the positive electrode active material layer 13 is composed of a positive electrode active material containing sulfur, the all-solid-state battery 10 is in a charged state at the time of manufacture, and the positive electrode active material layer 13 does not contain lithium. In this case, the positive electrode active material layer 13 at the time of first use (first discharge) after battery manufacture occludes lithium released from the negative electrode side. At this time, if the area of the active material layer of the electrode on the side that receives lithium is smaller than the active material layer of the electrode on the side that releases lithium, suitable movement of lithium is inhibited and lithium tends to precipitate.

Therefore, when the positive electrode active material layer 13 is made of a material that does not contain lithium, the area of the positive electrode solid electrolyte layer 15 in plan view is set to be larger than the area of the negative electrode solid electrolyte layer 16 in plan view. By doing so, it is possible to increase the size of the positive electrode active material layer 13 on the side that receives lithium at the time of first use (during first discharge), so that precipitation of lithium can be suppressed.

On the other hand, when the positive electrode active material layer 13 is made of a material containing lithium, as shown in FIG. The area is set to be larger than the area of . Examples of the material containing lithium include the above-mentioned layered rock salt type active material.

In this case, the positive electrode active material layer 13 releases lithium to the negative electrode side when used for the first time after manufacturing the battery. Therefore, when the positive electrode active material layer 13 is made of a material containing lithium, the area of the negative electrode solid electrolyte layer 16 in plan view is set to be larger than the area of the positive electrode solid electrolyte layer 15 in plan view. By doing so, the size of the negative electrode active material layer 14 on the side that receives lithium can be increased during the first use, so that precipitation of lithium can be suppressed.

In this way, when the all-solid-state battery 10 is used for the first time after being manufactured (first charge/discharge), by enlarging the active material layer of the electrode on the side that receives lithium, the active material layers of the positive electrode and the negative electrode can be Since the movement of lithium can be prevented from being inhibited due to the difference in size, it is possible to suppress the precipitation of lithium during the first use.

As described above, according to the all-solid-state battery 10 of the second embodiment, the solid electrolyte layers (15, 16) include the first solid electrolyte layer (positive electrode solid electrolyte layer 15) and the second solid electrolyte layer (negative electrode solid electrolyte layer 15). 16), and the first solid electrolyte layer and the second solid electrolyte layer have different areas in plan view. This allows the solid electrolyte layer (15 or 16) located at the outermost edge to function more strongly as a wall that prevents the active material layer, which has collapsed due to the application of strong pressure, from moving to the other pole. Therefore, it is possible to more effectively prevent the collapsed active material layer from moving beyond the solid electrolyte layer from the positive electrode to the negative electrode or from the negative electrode to the positive electrode. As a result, short-circuiting between the positive electrode and the negative electrode due to collapse of the active material layer can be more effectively suppressed.

Further, in the all-solid battery 10 of the second embodiment, the solid electrolyte layer 15 on the positive electrode side is the first solid electrolyte layer, the solid electrolyte layer 16 on the negative electrode side is the second solid electrolyte layer, and the positive electrode When the positive electrode active material contained in the active material layer 13 is made of a material that does not contain lithium, the area of the first solid electrolyte layer in plan view is set to be larger than that of the second solid electrolyte layer. As a result, when the positive electrode active material contained in the positive electrode active material layer 13 is composed of a material that does not contain lithium, the size of the positive electrode active material layer 13 on the side that receives lithium can be increased at the time of first use. Precipitation of lithium at the time of first use can be suppressed.

Further, in the all-solid battery 10 of the second embodiment, the solid electrolyte layer 15 on the positive electrode side is the first solid electrolyte layer, the solid electrolyte layer 16 on the negative electrode side is the second solid electrolyte layer, and the positive electrode When the positive electrode active material contained in the active material layer 13 is made of a material containing lithium, the area of the second solid electrolyte layer in plan view is set to be larger than that of the first solid electrolyte layer. As a result, when the positive electrode active material contained in the positive electrode active material layer 13 is composed of a material containing lithium, the negative electrode active material layer 14 on the side that receives lithium can be made large at the time of first use. Precipitation of lithium during use can be suppressed.

Although the embodiments of the present invention have been described above, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. do not have. Furthermore, the above embodiments can be combined as appropriate.

10... All solid battery 13... Positive electrode active material layer 14... Negative electrode active material layer 15... First solid electrolyte layer (positive electrode side solid electrolyte layer)
16...Second solid electrolyte layer (negative electrode side solid electrolyte layer)
19...Single cell layer

Claims (5)

a positive electrode including a positive electrode active material layer;
a negative electrode including a negative electrode active material layer;
A solid electrolyte layer interposed between the positive electrode and the negative electrode and composed of at least two layers, and at least one or more unit cell layers stacked,
The solid electrolyte layer is composed of two layers: a first solid electrolyte layer on the positive electrode side and a second solid electrolyte layer on the negative electrode side,
The first solid electrolyte layer and the second solid electrolyte layer have different areas in plan view,
The outer peripheral edge of the cell layer is
A slope provided at the outer peripheral edge of the first solid electrolyte layer and the positive electrode, the outer peripheral edge of the first solid electrolyte layer being inclined from the first solid electrolyte layer toward the end in the stacking direction of the positive electrode. An inclination formed to be located outside of the positive electrode, and an inclination formed such that the area of the unit cell layer in plan view becomes smaller toward the end of the positive electrode in the stacking direction, and/or ,
A slope provided at the outer peripheral edge of the second solid electrolyte layer and the negative electrode, the outer peripheral edge of the second solid electrolyte layer being inclined from the second solid electrolyte layer toward the end in the stacking direction of the negative electrode. The slope is formed to be located on the outside of the negative electrode, and the slope is formed such that the area of the unit cell layer in plan view becomes smaller toward the end of the negative electrode in the stacking direction. ,
The outer peripheral end of the solid electrolyte layer is located outside the outer peripheral ends of the positive electrode and the negative electrode,
All-solid-state battery. The all-solid-state battery according to claim 1 ,
When the positive electrode active material contained in the positive electrode active material layer is made of a material that does not contain lithium immediately after manufacturing the all- solid-state battery, the area of the first solid electrolyte layer in plan view is equal to that of the second solid electrolyte layer. set to be larger than the electrolyte layer,
All-solid-state battery. The all-solid-state battery according to claim 1 ,
When the positive electrode active material contained in the positive electrode active material layer is made of a material containing lithium immediately after manufacturing the all- solid-state battery, the area of the second solid electrolyte layer in plan view is equal to the area of the first solid electrolyte. set to be larger than the layer,
All-solid-state battery. The all-solid-state battery according to any one of claims 1 to 3 ,
If α is the angle between a perpendicular drawn perpendicularly to the surface direction of the solid electrolyte layer at the outer peripheral end of the solid electrolyte layer and an inclined plane formed at the outer peripheral end of the unit cell layer, then α is: It is set to satisfy the following formula 1,
The unit of t1 is mm,
All-solid-state battery.

The all-solid-state battery according to any one of claims 1 to 4 ,
Immediately after manufacturing the all-solid-state battery, the negative electrode active material contained in the negative electrode active material layer is composed of a metal containing lithium.
All-solid-state battery.

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