All-solid-state batteries

Abstract

To provide an all-solid battery capable of suppressing a short circuit between electrodes while suppressing an increase in the internal resistance of a solid electrolyte layer.SOLUTION: In an all-solid battery in which a negative electrode layer 1 containing a metallic lithium 12, a solid electrolyte layer 3, and a positive electrode layer 2 are laminated, in plan view, the outer periphery of the solid electrolyte layer 3 is located outside the outer periphery 11 of the negative electrode layer 1, and only a region of the solid electrolyte layer 3 overlapping the outer periphery of the negative electrode layer 1 includes a reaction area 4 containing a substance that reacts with the metallic lithium 12.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] Conventionally, all-solid-state batteries with a solid electrolyte layer between the positive and negative electrodes are known. When the negative electrode is metallic lithium, repeated charging causes the metallic lithium (lithium dendrites) to expand, and the stress associated with this expansion is applied to the solid electrolyte layer, causing cracks in the solid electrolyte layer. Furthermore, repeated charging is known to cause metallic lithium to penetrate into the cracks, causing a short circuit between the negative and positive electrodes.

[0003] Regarding the above problem, Patent Document 1 discloses that a sulfur-excess component layer is provided in a solid electrolyte layer, and when metallic lithium enters the sulfur-excess component layer, it reacts with sulfur to change it into lithium sulfide (LiS), which is an insulator, and the insulator acts as a barrier against metallic lithium, thereby suppressing a short circuit between the negative electrode and the positive electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2011 / 010552 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the configuration of Patent Document 1 has the effect of suppressing short circuits, the sulfur-excess component layer increases the internal resistance of the solid electrolyte layer.

[0006] An object of the present invention is to provide an all-solid-state battery that can suppress an increase in the internal resistance of a solid electrolyte layer while suppressing short circuits between electrodes. [Means for solving the problem]

[0007] The all-solid-state battery according to the present invention is an all-solid-state battery in which an anode layer containing metallic lithium, a solid electrolyte layer, and a cathode layer are stacked, and in plan view, the outer periphery of the solid electrolyte layer is located outside the outer periphery of the anode layer, and The area from the outer periphery of the negative electrode layer to the inner periphery of the negative electrode layer a reaction region containing a substance that reacts with metallic lithium; The reaction region has another region inside it where the concentration of the substance is lower than that of the reaction region, and the reaction region is in contact with the negative electrode layer. [Effects of the Invention]

[0008] According to the present invention, In a configuration in which the outer periphery of the solid electrolyte layer is located outside the outer periphery of the negative electrode layer in a plan view, The stress applied by the negative electrode layer to the solid electrolyte layer is shown in plan view. a region extending from the outer periphery of the solid electrolyte layer to the inner side of the outer periphery of the negative electrode layer; Therefore, even if cracks occur in the solid electrolyte layer, the cracks are generated intensively in the region where the stress is concentrated, and the occurrence of cracks in the central portion when the solid electrolyte layer is viewed from above can be reduced. Therefore, in the central portion where the current density is high, an increase in internal resistance due to cracks can be suppressed, and an increase in the internal resistance of the entire all-solid-state battery can be suppressed. In a configuration in which the outer periphery of the solid electrolyte layer is located outside the outer periphery of the negative electrode layer in a plan view, In response to the above-mentioned concentration of stress, the reaction region in the solid electrolyte layer is, in plan view, a region extending from the outer periphery of the solid electrolyte layer to the inner side of the outer periphery of the negative electrode layer; Therefore, in the central portion of the solid electrolyte layer, which is located inside the reaction region, an increase in internal resistance due to the reaction region can be avoided, and an increase in the internal resistance of the entire all-solid-state battery can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are schematic diagrams illustrating a cell layer included in the all-solid-state battery of the first embodiment, in which FIG. 1A is a side view, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1C is a partial plan view illustrating cracks formed in the solid electrolyte layer. [Figure 2]2A and 2B are side views of a cell layer included in the all-solid-state battery of the first embodiment, in which FIG. 2A is a diagram for explaining a crack formed in the solid electrolyte layer, and FIG. 2B is a diagram for explaining a case where metallic lithium has entered the crack shown in FIG. 2A. [Figure 3] 3A and 3B are cross-sectional views taken along line AA in FIG. 1A, where FIG. 3A is a diagram for explaining a crack formed in the solid electrolyte layer, and FIG. 3B is a diagram and a partially enlarged view for explaining a case where metallic lithium has entered the crack shown in FIG. 3A. [Figure 4] 4A and 4B are cross-sectional views of a cell layer included in the all-solid-state battery of the first comparative example, in which FIG. 4A is a cross-sectional view of the cell layer, FIG. 4B is a diagram for explaining a crack formed in the sulfur-excess component layer 31, and FIG. 4C is a diagram and a partially enlarged view for explaining a case where metallic lithium has entered the crack shown in FIG. 4B. [Figure 5] 5A and 5B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer included in the all-solid-state battery of the second comparative example, where FIG. 5A is a cross-sectional view of the cell layer, FIG. 5B is a diagram for explaining a crack formed in the solid electrolyte layer, and FIG. 5C is a diagram and a partially enlarged view for explaining a case where metallic lithium has entered the crack shown in FIG. 5B. [Figure 6] 6A and 6B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer included in the all-solid-state battery of the second embodiment, in which FIG. 6A is a cross-sectional view of the cell layer, FIG. 6B is a diagram for explaining a crack formed in the solid electrolyte layer, and FIG. 6C is a diagram and a partially enlarged view for explaining a case where metallic lithium has entered the crack shown in FIG. 6B. [Figure 7] 7A and 7B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer included in an all-solid-state battery according to a third embodiment, in which FIG. 7A is a cross-sectional view of the cell layer, FIG. 7B is a diagram for explaining a crack formed in the solid electrolyte layer, and FIG. 7C is a diagram and a partially enlarged view for explaining a case where metallic lithium has entered the crack shown in FIG. 7B. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Outline of the first embodiment] An all-solid-state battery 100 according to a first embodiment of the present invention will be described.

[0011] 1A and 1B are schematic diagrams illustrating a cell layer 9 included in an all-solid-state battery 100 according to the first embodiment, in which FIG. 1A is a side view, FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A, and FIG. 1C is a partial plan view illustrating cracks 5 formed in a solid electrolyte layer 3.

[0012] The all-solid-state battery 100 of this embodiment is a so-called stacked-type all-solid-state battery 100 that houses a power generating element in which a plurality of unit cell layers 9 described below are stacked and sealed with a laminate film that is a battery exterior material. The stacked-type battery can make the battery compact and increase its capacity.

[0013] However, the unit cell layer 9 housed in the all-solid-state battery 100 to which the present invention is applied does not necessarily have to be a multi-layer structure, and may be a single layer. The unit cell layer 9 is configured in the shape of, for example, a circular or rectangular sheet before being housed in the battery exterior material. Furthermore, the appearance and the internal electrical connection state (electrode structure) of the all-solid-state battery 100 of this embodiment are not particularly limited.

[0014] The appearance of the all-solid-state battery 100 may be circular, elliptical, or rectangular in plan view. Alternatively, it may be cylindrical in shape, in which a single or multiple cell layers 9 are wound and housed. The electrode structure of the all-solid-state battery 100 may be either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). In other words, the configuration of the all-solid-state battery 100 other than the configuration of the cell layers 9 described below is not particularly limited, regardless of whether it is publicly known or not.

[0015] The cell layer 9 includes a laminated structure of an anode layer 1 containing metallic lithium 12, a solid electrolyte layer 3, and a cathode layer 2. Although not shown, the cell layer 9 further includes a cathode current collector and an anode current collector. The cathode current collector is in contact with the cathode layer 2 and is disposed so as to sandwich the cathode layer 2 together with the solid electrolyte layer 3. The anode current collector is in contact with the anode layer 1 and is disposed so as to sandwich the anode layer 1 together with the solid electrolyte layer 3. Details of each component of the all-solid-state battery 100 will be described later.

[0016] [First Comparative Example] Here, the problem solved by the all-solid-state battery 100 of the first embodiment will be described with reference to Fig. 4 showing the structure of an all-solid-state battery 100A of a first comparative example. Note that the terms indicating the up-down direction (e.g., top surface, bottom surface) used in the following description are expressions that correspond to the up-down direction in the drawing, and are not necessarily intended to correspond to the up-down direction in the actual direction of gravity.

[0017] 4A and 4B are cross-sectional views of a cell layer 9A included in an all-solid-state battery 100A of a first comparative example, where Fig. 4A is a cross-sectional view of the cell layer 9A, Fig. 4B is a diagram for explaining a crack 5 formed in the sulfur-excess component layer 31, and Fig. 4C is a diagram and a partially enlarged view for explaining a case where metallic lithium 12 has entered the crack 5 shown in Fig. 4B. The cell layer 9A of the first comparative example is similar to that disclosed in Patent Document 1.

[0018] As shown in FIG. 4(a), the cell layer 9A is configured such that a solid electrolyte layer 3 is sandwiched between a positive electrode layer 2 and an anode layer 1 containing metallic lithium 12. A sulfide-based solid electrolyte or the like is used for the solid electrolyte layer 3. The sulfur concentration in the solid electrolyte layer 3 is set to less than 10 mol %. A sulfur-excess component layer 31 containing elemental sulfur is formed in an intermediate region in the thickness direction of the solid electrolyte layer 3, and the sulfur concentration in the sulfur-excess component layer 31 is set to 10 mol % or more.

[0019] 4(a), consider a case where metallic lithium 12 (lithium dendrite) contained in the negative electrode layer 1 elongates each time charging is repeated, causing the solid electrolyte layer 3 to receive stress from the negative electrode layer 1, resulting in the occurrence of cracks 5 in the solid electrolyte layer 3 that reach the sulfur-excess component layer 31, as shown in FIG. 4(b). In this case, if charging is further repeated in the cell layer 9, metallic lithium 12 will enter the cracks 5 and reach the sulfur-excess component layer 31.

[0020] 4(c), when the metallic lithium 12 reaches the sulfur-excess component layer 31, the metallic lithium 12 reacts with sulfur to form LiS (insulator 6). Therefore, the insulator 6 acts as a barrier to the metallic lithium 12, thereby reducing short circuits between the negative electrode layer 1 and the positive electrode layer 2.

[0021] Incidentally, when the solid electrolyte layer 3 is entirely covered with the anode layer 1 as in the cell layer 9A shown in FIG. 4(a), it is difficult to predict which part of the solid electrolyte layer 3 the stress applied by the anode layer 1 to the solid electrolyte layer 3 will concentrate on and cause cracks 5 to occur. For this reason, it is necessary to form the sulfur-excess component layer 31 over the entire surface of the solid electrolyte layer 3 of the cell layer 9A shown in FIG. 4(a). However, the sulfur-excess component layer 31 has lower lithium ion conductivity and higher resistivity than the parts of the solid electrolyte layer 3 other than the sulfur-excess component layer 31, and therefore the internal resistance of the entire cell layer 9A increases.

[0022] Therefore, in the present invention, the location of stress concentration is limited to a specific region, and a reaction region 4 that reacts with metallic lithium 12 is formed only in that region, thereby realizing a single cell layer 9 (all-solid-state battery 100) in which an increase in internal resistance is suppressed.

[0023] [Details of the first embodiment] 1, the negative electrode layer 1 is disposed so as to be located inside the outer periphery of the solid electrolyte layer 3 in a plan view (viewed from the stacking direction). In other words, the outer periphery of the solid electrolyte layer 3 is disposed so as to be located outside the outer periphery 11 of the negative electrode layer 1 in a plan view.

[0024] Also, as shown in Figure 1(b), flat In person, In the region from the outer periphery of the solid electrolyte layer 3 to the inner periphery of the negative electrode layer 1, A reaction region 4 containing a substance that reacts with metallic lithium 12 contained in the negative electrode layer 1 is disposed. Furthermore, in a region inside the reaction region 4, another region in which the concentration of the substance is lower than that of the reaction region 4 is arranged.

[0025] Reaction region 4 is shown in plan view as follows: A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 More specifically, the reaction region 4 is formed as follows in a plan view: A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 It is formed in a circumferential frame shape, for example. A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 If is circular, it will be formed into a circular ring, A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 If is rectangular, it is formed into a rectangular frame shape.

[0026] The reaction region 4 is applied as a structure in which sulfur or carbon is at a higher concentration than in other parts of the solid electrolyte layer 3, or as a structure in which an ionic liquid is impregnated into the solid electrolyte layer 3 as an impregnation material. When the reaction region 4 contains sulfur, the metallic lithium 12 that reaches the reaction region 4 changes into an insulator 6 (Li2S). When the reaction region 4 contains carbon, the metallic lithium 12 that reaches the reaction region 4 changes into an insulator 6 (Li2S). x C) changes to

[0027] Note that any substance other than sulfur or carbon can be used as long as it has a higher potential than lithium, is solid within the operating temperature range of the cell layer 9 (all-solid-state battery 100), and does not react with hydrogen sulfide or the like that may be generated within the cell layer 9. For example, aluminum, stainless steel, metal oxide (LTO), etc. can be used.

[0028] The reaction region 4 can be formed using these substances alone, or the reaction region 4 can be formed by adding these substances at a high concentration to the portion of the solid electrolyte layer 3 that will become the reaction region 4.

[0029] The impregnating material is a material that is impregnated into the portion of the solid electrolyte layer 3 that will become the reaction region 4, and an ionic liquid is used. Ionic liquids have the characteristics of salts, such as high polarity, non-volatility, flame retardancy, heat resistance, and conductivity, and also have a low melting point and remain liquid even at around room temperature. In this embodiment, an ionic liquid that reacts with Li ions is used. In addition, in this embodiment, an ionic liquid with a viscosity coefficient of approximately several tens to 100 [mPa·s] is used, which makes it possible to realize a configuration that is relatively easy to impregnate and that is less likely to leak after impregnation.

[0030] As an ionic liquid (salt of cation and anion), for example, the cation is ethylmethylimidazole (EMI) and the anion is one of Cl, Br, CF3SO3, PF6, BF4, or a combination thereof. Other ionic liquids that can be used include a combination of pyridinium (cation) with one of the above anions and TFSI (anion), and a combination of a tetraalkylammonium derivative (cation) with TFSI (anion).

[0031] When metallic lithium 12 comes into contact with the impregnating material made of ionic liquid, it changes into lithium salt (insulator 6).

[0032] When the anode layer 1 is disposed on the solid electrolyte layer 3 as shown in Figures 1(a) and 1(b), the inventors of the present application have found that the anode layer 1 (metallic lithium 12) extends in the planar direction toward the outer periphery 11 due to charging of the cell layer 9, but that stress is concentrated in the solid electrolyte layer 3 at the portion of the anode layer 1 that contacts the outer periphery 11, causing cracks 5 to occur centered around that portion.

[0033] 1(c), the anode layer 1 applies a stress to the solid electrolyte layer 3 at a position where the solid electrolyte layer 3 contacts the outer periphery 11 of the anode layer 1, which compresses the anode layer 1 in the radial direction (diameter expansion) and a stress to expand the anode layer 1 in the circumferential direction, which causes the crack 5. The crack 5 tends to extend in the radial direction (diameter expansion) of the anode layer 1 from the position where the solid electrolyte layer 3 contacts the outer periphery 11 of the anode layer 1.

[0034] On the other hand, the inventors of the present application have also found that it is possible to suppress the concentration of stress in areas other than the area where stress is concentrated, for example, in the center of the surface direction of the solid electrolyte layer 3. Therefore, as shown in FIG. 1(b), the reaction region 4 has a shape similar to that shown in FIG. From the outer periphery of the solid electrolyte layer 3 to the region inside the outer periphery of the negative electrode layer 1 Just placing it is enough.

[0035] Fig. 2 is a side view of a cell layer 9 included in the all-solid-state battery 100 of the first embodiment, Fig. 2(a) is a diagram for explaining a crack 5 formed in the solid electrolyte layer 3, and Fig. 2(b) is a diagram for explaining a case where metallic lithium 12 has entered the crack 5 shown in Fig. 2(a). Fig. 3 is a cross-sectional view taken along line AA in Fig. 1(a), Fig. 3(a) is a diagram for explaining a crack 5 formed in the solid electrolyte layer 3, and Fig. 3(b) is a diagram and a partially enlarged view for explaining a case where metallic lithium 12 has entered the crack 5 shown in Fig. 3(a).

[0036] As described above, when charging the cell layer 9, cracks 5 occur in the solid electrolyte layer 3 at positions where the solid electrolyte layer 3 contacts the outer periphery 11 of the negative electrode layer 1, as shown in Figures 2(a) and 3(a), and the cracks 5 reach the reaction region 4.

[0037] When the cell layer 9 is further repeatedly charged, metallic lithium 12 (lithium dendrites) penetrates the cracks 5 and reaches the reaction region 4. As shown in FIGS. 2(b) and 3(b), the metallic lithium 12 that reaches the reaction region 4 reacts with sulfur in the reaction region 4 and transforms into an insulator 6 (e.g., LiS). Therefore, the insulator 6 prevents further penetration of the metallic lithium 12, thereby reducing short circuits between the anode layer 1 and the cathode layer 2. Meanwhile, the region of the solid electrolyte layer 3 that is inside the reaction region 4 is the region where the current density is highest, but this region, like the reaction region 4, has a low concentration of sulfur components and a low resistivity. Therefore, an increase in the internal resistance of the entire cell layer 9, i.e., the entire all-solid-state battery 100, can also be suppressed.

[0038] [Effects of the first embodiment] According to the all-solid-state battery 100 of the first embodiment, in the all-solid-state battery 100 (single cell layer 9) in which the negative electrode layer 1 containing metallic lithium 12, the solid electrolyte layer 3, and the positive electrode layer 2 are stacked, the outer periphery of the solid electrolyte layer 3 is located outside the outer periphery 11 of the negative electrode layer 1 in a plan view, and From the outer periphery to the region inside the outer periphery of the negative electrode layer 1 A reaction region 4 containing a substance that reacts with metallic lithium 12 is provided. The reaction region 4 is in contact with the negative electrode layer 1. .

[0039] With the above configuration, In a configuration in which the outer periphery of the solid electrolyte layer 3 is located outside the outer periphery of the negative electrode layer 1 in a plan view, The stress applied to the solid electrolyte layer 3 by the negative electrode layer 1 is expressed as the stress of the solid electrolyte layer 3 in plan view. The region from the outer periphery to the inner periphery of the negative electrode layer 1 Therefore, even if cracks 5 occur in the solid electrolyte layer 3, the cracks 5 are generated intensively in the region where the stress is concentrated, and the occurrence of cracks 5 in the center when the solid electrolyte layer 3 is viewed from above can be reduced. Therefore, in the center where the current density is high, an increase in internal resistance caused by the cracks 5 can be suppressed, and an increase in the internal resistance of the entire all-solid-state battery 100 can be suppressed. In addition, In a configuration in which the outer periphery of the solid electrolyte layer is located outside the outer periphery of the negative electrode layer in a plan view, In response to the above-mentioned concentration of stress, the reaction region 4 in the solid electrolyte layer 3 has the following characteristics in plan view: A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 It is sufficient to form the insulating layer 6 on the central portion of the solid electrolyte layer 3, and it is not necessary to form it on the entire surface of the solid electrolyte layer 3. Therefore, an increase in internal resistance due to the reaction region 4 can be avoided in the central portion of the solid electrolyte layer 3, which is located inside the reaction region 4, and an increase in the internal resistance of the entire all-solid-state battery 100 can be suppressed. Furthermore, since the reaction region 4 is arranged so as to overlap the region where the crack 5 is formed, even if the metallic lithium 12 enters the crack 5, the metallic lithium 12 becomes the insulator 6 in the reaction region 4, and the insulator 6 acts as a barrier against the metallic lithium 12, thereby reducing short circuits between the electrodes.

[0040] In the first embodiment, the reaction region 4 is A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 For example, A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1 is rectangular in plan view, the reaction region 4 may be formed in the shape of a rectangular frame that surrounds the rectangular shape, A region extending from the outer periphery of the solid electrolyte layer 3 to the inner side of the outer periphery of the negative electrode layer 1is circular in plan view, reaction region 4 may be formed in a ring shape that surrounds the circular shape. Therefore, in the central part of solid electrolyte layer 3 that is inside frame-shaped (ring-shaped) reaction region 4, an increase in internal resistance due to reaction region 4 can be avoided, and an increase in the internal resistance of the entire all-solid-state battery 100 can be suppressed.

[0041] In the first embodiment, the reaction region 4 is formed by making the concentration of sulfur or carbon higher than that in other parts of the solid electrolyte layer 3. In another embodiment, the reaction region 4 is formed by impregnating the solid electrolyte layer 3 with an impregnation material made of an ionic liquid. This allows the reaction region 4 to be formed with a simple configuration.

[0042] [Second Comparative Example] 5A and 5B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer 9 included in an all-solid-state battery 100 of the second comparative example, in which FIG. 5A is a cross-sectional view of the cell layer 9, FIG. 5B is a diagram for explaining a crack 5 formed in the solid electrolyte layer 3, and FIG. 5C is a diagram and a partially enlarged view for explaining a case where metallic lithium 12 has entered the crack 5 shown in FIG. 5B.

[0043] 5(a), the second comparative example has the same configuration as the first embodiment, except that the reaction region 4 is disposed in the center in the thickness direction of the solid electrolyte layer 3. Therefore, the outer periphery 11 of the anode layer 1 and the reaction region 4 are spaced apart from each other in the thickness direction.

[0044] When charging is repeated in the above configuration, as shown in FIG. 5(b), cracks 5 originate from the position where the solid electrolyte layer 3 contacts the outer periphery 11 of the anode layer 1. However, the direction of the cracks may not be along the thickness direction of the solid electrolyte layer 3 but may be inclined toward the center of the solid electrolyte layer 3 in a plan view. In this case, the cracks 5 avoid the reaction region 4 and form inside the reaction region 4. Therefore, by further repeating charging, metallic lithium 12 enters the cracks 5 as shown in FIG. 5(c), but because the metallic lithium 12 does not contact the reaction region 4, it does not transform into the insulator 6 (FIG. 3). This can cause a short circuit between the anode layer 1 and the cathode layer 2.

[0045] The second embodiment described below has a configuration that reduces short circuits between the negative electrode layer 1 and the positive electrode layer 2 even when the crack 5 occurs.

[0046] [Second embodiment] 6A and 6B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer 9 included in an all-solid-state battery 100 according to a second embodiment, in which FIG. 6A is a cross-sectional view of the cell layer 9, FIG. 6B is a diagram for explaining a crack 5 formed in the solid electrolyte layer 3, and FIG. 6C is a diagram and a partially enlarged view for explaining a case where metallic lithium 12 has entered the crack 5 shown in FIG. 6B.

[0047] As shown in FIG. 6(a), in the cell layer 9 of the all-solid-state battery 100 of the second embodiment, the reaction region 4 of the solid electrolyte layer 3 is exposed on the upper surface and is in contact with the anode layer 1 (particularly the outer periphery 11 of the anode layer 1). As shown in FIG. 6(a), the reaction region 4 is arranged to extend inside the outer periphery 11 of the negative electrode layer 1 in a cross-sectional view. 6(b), even if a crack 5 occurs, the starting point of the crack 5 is the reaction region 4. Therefore, as shown in FIG. 6(c), metallic lithium 12 that has entered the crack 5 comes into contact with the reactant in the reaction region 4 at a position relatively shallow from the upper surface of the solid electrolyte layer 3, and becomes an insulator 6.

[0048] In addition, in FIG. 6(b) and FIG. 6(c), the crack 5 is inclined so as to extend toward the outer periphery of the solid electrolyte layer 3. However, even if the crack 5 extends toward the inside of the solid electrolyte layer 3, Since the reaction region 4 is disposed inside the outer periphery 11 of the negative electrode layer 1, The starting point of the crack 5 is the reaction region 4. As a result, the metallic lithium 12 extending from the anode layer 1 to the crack 5 comes into contact with the reactants in the reaction region 4 and becomes an insulator 6, and the insulator 6 acts as a barrier against the metallic lithium 12, thereby reducing short circuits between the anode layer 1 and the cathode layer 2.

[0049] [Third embodiment] 7A and 7B are cross-sectional views (corresponding to the cross-sectional view along line AA in FIG. 1A) of a cell layer 9 included in an all-solid-state battery 100 according to a third embodiment, in which FIG. 7A is a cross-sectional view of the cell layer 9, FIG. 7B is a diagram for explaining a crack 5 formed in the solid electrolyte layer 3, and FIG. 7C is a diagram and a partially enlarged view for explaining a case where metallic lithium 12 has entered the crack 5 shown in FIG. 7B.

[0050] The cell layer 9 of the third embodiment is configured to be able to further reduce short circuits between electrodes than the cell layer 9 of the second embodiment.

[0051] That is, as shown in Fig. 7(a), in the third embodiment, reaction region 4 is arranged in a cross-sectional view so as to include a tapered region whose apex is a position where it contacts the outer periphery 11 of negative electrode layer 1 and whose width increases toward positive electrode layer 2. More specifically, as shown in Fig. 7(a), reaction region 4 is formed so that dashed line 7 indicating the boundary of the tapered region intersects with the bottom surface of reaction region 4 (the surface facing positive electrode layer 2). In particular, reaction region 4 is formed so that dashed line 7 does not intersect with inner circumferential surface 41 of reaction region 4. In other words, the inner circumferential surface 41 of the reaction region 4 is located inside the outer circumferential surface 11 of the negative electrode layer 1 .

[0052] As a result, the length of the crack 5 becomes longer than at least the thickness of the reaction region 4, which increases the opportunities for contact between the metallic lithium 12 and the reaction material and for the formation of the insulator 6, thereby reducing short circuits between the negative electrode layer 1 and the positive electrode layer 2.

[0053] The inventors of the present application have found that the stress applied by the outer periphery 11 of the anode layer 1 to the solid electrolyte layer 3 (reaction region 4) originates from the contact position of the reaction region 4 with the outer periphery 11 of the anode layer 1 and initially extends in any direction with a half apex angle of 45 degrees or less with respect to the thickness direction (the direction toward the cathode layer 2). Therefore, the inventors of the present application have found that the crack 5 that occurs in the reaction region 4 originates from the contact position of the reaction region 4 with the outer periphery 11 of the anode layer 1 and initially extends in any direction with a half apex angle of 45 degrees or less with respect to the thickness direction (the direction toward the cathode layer 2).

[0054] 7(a), (b), and (c), the reaction region 4 may be formed to include a tapered region where the inclination angle of the broken line 7 is 45 degrees. This prevents the tip of the crack 5 from protruding from the inner circumferential surface 41 of the reaction region 4, thereby reducing short circuits between the negative electrode layer 1 and the positive electrode layer 2 caused by the penetration of metallic lithium 12 into the tip side of the crack 5.

[0055] As shown in Figure 7(b), even if crack 5 is formed at an inclination angle of 45 degrees from the position where it contacts the outer periphery 11 of the negative electrode layer 1 in reaction region 4 toward the center of solid electrolyte layer 3, its end will not protrude from the inner periphery 41 of reaction region 4.

[0056] Therefore, as shown in FIG. 7(c), even if metallic lithium 12 enters crack 5, it reacts with the reactant in reaction region 4 at the tip of crack 5, for example, and turns into insulator 6, and this insulator 6 acts as a barrier against metallic lithium 12, thereby reducing short-circuiting between negative electrode layer 1 and positive electrode layer 2.

[0057] The main components of the cell layer 9 that constitutes the all-solid-state battery 100 according to this embodiment will be described below.

[0058] [Current collector] The material constituting the positive electrode current collector (not shown) and the negative electrode current collector (not shown) (hereinafter collectively referred to as current collectors) is not particularly limited as long as it functions as a current collector applicable to the all-solid-state battery 100 in the technical field related to the present invention. Known materials may be used as the constituent material of the current collectors, and for example, metals and conductive resins may be used.

[0059] [Negative electrode layer 1] The negative electrode layer 1 contains a negative electrode active material. The type of the negative electrode active material is not particularly limited, but examples thereof include 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. Examples of metal oxides include Nb2O5, Li4Ti5O 12 Examples include silicon-based negative electrode active materials and tin-based negative electrode active materials. Silicon and tin belong to Group 14 elements and are known to be negative electrode active materials that can significantly improve the capacity of nonaqueous electrolyte secondary batteries. These elements can absorb and release a large number of charge carriers (such as lithium ions) per unit volume (mass), resulting in high-capacity negative electrode active materials. As the silicon-based negative electrode active material, it is preferable to use Si as the negative electrode active material. Similarly, it is also preferable to use silicon oxides such as SiOx (0.3≦x≦1.6) disproportionated into two phases: a Si phase and a silicon oxide phase. In this case, the range of x is more preferably 0.5≦x≦1.5, and even more preferably 0.7≦x≦1.2. Furthermore, silicon-containing alloys (silicon-containing alloy-based negative electrode active materials) may be used. On the other hand, examples of negative electrode active materials containing tin (tin-based negative electrode active materials) include simple Sn, tin alloys (Cu-Sn alloys, Co-Sn alloys), amorphous tin oxides, and tin silicon oxides. Among these, amorphous tin oxides include SnB 0.4 P 0.6 O 3.1Examples of tin silicon oxides include SnSiO3. Metals containing lithium (Li) may also be used as the negative electrode active material. Such negative electrode active materials are not particularly limited as long as they are active materials containing lithium, and examples include metallic lithium 12 and lithium-containing alloys. Examples of lithium-containing alloys include alloys of Li with at least one of In, Al, Si, and Sn. In some cases, two or more negative electrode active materials may be used in combination. Of course, negative electrode active materials other than those mentioned above may also be used. In terms of high capacity, the negative electrode active material preferably contains metallic lithium 12, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably contains metallic lithium 12.

[0060] The shape of the negative electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the negative electrode active material is particulate, its average particle size (D50) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D50) of the active material can be measured by a laser diffraction scattering method.

[0061] The content of the negative electrode active material in the negative electrode layer 1 is not particularly limited, but is preferably within the range of 40 to 99 mass %, and more preferably within the range of 50 to 90 mass %, for example.

[0062] The negative electrode layer 1 preferably further includes a solid electrolyte. When the negative electrode layer 1 includes a solid electrolyte, the ionic conductivity of the negative electrode layer 1 can be improved. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and a sulfide solid electrolyte is preferred.

[0063] Examples of sulfide solid electrolytes include LiI-Li2S-SiS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2OLiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, and Li2S-SiS2-LiC l , Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (however, m , n is a positive number, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (however, x , y is a positive number, and M is any of P, Si, Ge, B, Al, Ga, and In. The term "LiS-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing LiS and P2S5, and the same applies to other terms.

[0064] The sulfide solid electrolyte may have, for example, a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of sulfide solid electrolytes having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes known as LPS (for example, Li7P3S 11 ) can be mentioned. In addition, examples of sulfide solid electrolytes include Li (4-x) Ge (1-x) P x S4( xIt is also possible to use an LGPS or the like represented by (where 0 < x < 1). Among these, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing P element, and more preferably a material mainly composed of Li2S-P2S5. Furthermore, the sulfide solid electrolyte may contain a halogen (F, Cl, Br, I).

[0065] Also, when the sulfide solid electrolyte is a Li2S-P2S5 system, the ratio of Li2S and P2S5 is preferably within the range of Li2S:P2S5 = 50:50 to 100:0 in terms of molar ratio, and more preferably Li2S:P2S5 = 70:30 to 80:20.

[0066] Also, the sulfide solid electrolyte may be a sulfide glass, a crystallized sulfide glass, or a crystalline material obtained by a solid-phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (such as a ball mill) on a raw material composition. Also, the crystallized sulfide glass can be obtained, for example, by performing heat treatment on the sulfide glass at a temperature above the crystallization temperature. Also, the ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25 °C) is, for example, 1×10 -5 S / cm or more is preferable, and 1×10 -4 S / cm or more is more preferable. The value of the ionic conductivity of the solid electrolyte can be measured by an alternating current impedance method.

[0067] Examples of the oxide solid electrolyte include compounds having a NASICON-type structure. As an example of a compound having a NASICON-type structure, 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 A lx Ti 2-x (PO4)3 (0 ≤ x ≤ 2) (LATP), etc. are mentioned. Also, as another example of the oxide solid electrolyte, LiLaTiO (for example, Li 0.3 4La0.5 1TiO3), LiPON (e.g., Li2.9PO3.3N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O 12 ) etc.

[0068] The shape of the solid electrolyte may be, for example, a particulate shape such as a spherical shape or an oval spherical shape, or a thin film shape. When the solid electrolyte is particulate, its average particle size (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 size (D50) is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

[0069] The content of the solid electrolyte in the negative electrode layer 1 is, for example, preferably in the range of 1 to 60 mass %, and more preferably in the range of 10 to 50 mass %. However, when lithium metal is used as the negative electrode active material constituting the negative electrode layer 1, the content of the solid electrolyte in the negative electrode layer 1 is preferably zero. Note that examples of the form of the lithium metal used here include lithium metal foil, lithium alloy metal foil (alloy species: Mg, Al, In, etc.), and lithium vapor-deposited on a substrate (substrate: SUS foil, Al foil, etc.).

[0070] The negative electrode layer 1 may further contain at least one of a conductive additive and a binder in addition to the above-mentioned negative electrode active material and solid electrolyte.

[0071] Examples of conductive additives 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-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.), carbon nanotubes (CNTs), and carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.), but are not limited to these.

[0072] Furthermore, the material used as the binder is not particularly limited, and any known material in the technical field may be used as long as it functions as a binder applicable to the all-solid-state battery 100.

[0073] The thickness of the negative electrode layer 1 varies depending on the intended configuration of the all-solid-state battery 100, but is preferably within the range of 0.1 to 1000 μm, for example.

[0074] [Positive electrode layer 2] The positive electrode layer 2 preferably contains a sulfur-containing positive electrode active material. The type of sulfur-containing positive electrode active material is not particularly limited, but examples include elemental sulfur (S) as well as particles or thin films of organic or inorganic sulfur compounds. Any material can be used as long as it utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging. Examples of organic sulfur compounds include disulfide compounds, sulfur-modified polyacrylonitrile, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), and polycarbon sulfide, as typified by the compounds described in International Publication No. 2010 / 044437. Among these, disulfide compounds, sulfur-modified polyacrylonitrile, and rubeanic acid are preferred, with sulfur-modified polyacrylonitrile being particularly preferred. As disulfide compounds, dithiobiurea derivatives, compounds having a thiourea group, a thioisocyanate group, or a thioamide group are more preferred. Here, sulfur-modified polyacrylonitrile is a modified polyacrylonitrile containing sulfur atoms, which is obtained by mixing sulfur powder with polyacrylonitrile and heating the mixture under an inert gas or under reduced pressure. Its estimated structure is, for example, as shown in Chem. Mater. 2011, 23, 5024-5028, in which polyacrylonitrile is ring-closed to form a polycyclic ring, and at least a part of S is bonded to C. The compound described in this document has a peak at 1330 cm in the Raman spectrum. -1 and 1560cm -1 There is a strong peak signal near 307 cm -1 , 379cm-1 , 472cm -1 , 929cm -1 A peak is present around 1000 s. On the other hand, inorganic sulfur compounds are preferred due to their excellent stability. Specific examples include elemental sulfur (S), S-carbon composites, TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, Li2S, MoS2, and MoS3. Among these, S, S-carbon composites, TiS2, TiS3, TiS4, FeS2, and MoS2 are preferred, elemental sulfur (S), S-carbon composites, TiS2, and FeS2 are more preferred, and elemental sulfur (S) is particularly preferred. Here, the S-carbon composite refers to a composite containing sulfur powder and a carbon material, which is obtained by subjecting these to heat treatment or mechanical mixing. More specifically, it refers to a composite in which sulfur is distributed on the surface or within the pores of the carbon material, in which sulfur and the carbon material are uniformly dispersed at the nano-level and aggregated to form particles, in which the carbon material is distributed on the surface or within fine sulfur powder, or in which a combination of these states is present.

[0075] The positive electrode layer 2 may contain a sulfur-free positive electrode active material instead of a sulfur-containing positive electrode active material. Examples of sulfur-free positive electrode active materials include layered rock salt active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2; LiMn2O4; and LiNi 0.5 Mn 1.5 Examples of oxide active materials include spinel-type active materials such as LiFePO4 and LiMnPO4, olivine-type active materials such as LiFeSiO4 and LiMnSiO4, and Si-containing active materials such as LiFeSiO4 and LiMnSiO4. 12 Examples include:

[0076] In some cases, two or more positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those mentioned above may also be used.

[0077] The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the positive electrode active material is particulate, its average particle size (D50) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D50) of the active material can be measured by a laser diffraction scattering method.

[0078] The content of the positive electrode active material in the positive electrode layer 2 is not particularly limited, but is preferably within the range of 40 to 99 mass %, and more preferably within the range of 50 to 90 mass %, for example.

[0079] Like the negative electrode layer 1, the positive electrode layer 2 may also further contain a conductive additive and / or a binder.

[0080] [Solid electrolyte layer 3] The solid electrolyte layer 3 included in the all-solid-state battery 100 according to this embodiment contains a solid electrolyte as a main component, and is a layer interposed between the above-described anode layer 1 and cathode layer 2. The specific form of the solid electrolyte contained in the solid electrolyte layer 3 is the same as that described above, and therefore a detailed description thereof will be omitted here.

[0081] The content of the solid electrolyte in the solid electrolyte layer 3 is, for example, preferably in the range of 10 to 100 mass %, more preferably in the range of 50 to 100 mass %, and even more preferably in the range of 90 to 100 mass %.

[0082] The solid electrolyte layer 3 may further contain a binder in addition to the above-described solid electrolyte. The specific form of the binder that can be contained in the solid electrolyte layer 3 is the same as that described above, and therefore a detailed description thereof will be omitted here.

[0083] The thickness of each solid electrolyte layer 3 varies depending on the intended configuration of the all-solid-state battery 100, but is preferably within the range of 0.1 to 1000 μm, and more preferably within the range of 0.1 to 300 μm, for example.

[0084] Although not shown, the all-solid-state battery 100 may include a positive electrode current collector member and a negative electrode current collector member for extracting electric power from the one or more contained single cell layers 9 to the outside of the all-solid-state battery 100. In this case, the material constituting the current collectors is not particularly limited, and any known highly conductive material conventionally used as a current collector for a secondary battery can be used.

[0085] Although not shown, a positive electrode current collector (not shown) and a negative electrode current collector (not shown) may be electrically connected to the positive electrode current collector and the negative electrode current collector via a positive electrode lead and a negative electrode lead, respectively. Materials used in known lithium ion secondary batteries may be similarly employed as constituent materials of the positive electrode and the negative electrode leads.

[0086] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate. [Explanation of symbols]

[0087] 100 solid state battery 1. Negative electrode layer 2 Positive electrode layer 3 Solid electrolyte layer 4. Reaction Area 5. Crack 6. Insulators 9 Cell Layer

Claims

1. In an all-solid-state battery in which a negative electrode layer containing metallic lithium, a solid electrolyte layer, and a positive electrode layer are stacked, In a plan view, the outer periphery of the solid electrolyte layer is located outside the outer periphery of the anode layer, and a reaction region containing a substance that reacts with the metallic lithium is provided in a region from the outer periphery of the solid electrolyte layer to the inner side of the outer periphery of the anode layer, and another region is provided inside the reaction region in which the concentration of the substance is lower than in the reaction region, and the reaction region is in contact with the anode layer. All-solid-state battery.

2. The all-solid-state battery according to claim 1 , wherein the reaction region has a frame shape that surrounds the outer periphery of the solid electrolyte layer and the region inside the outer periphery of the negative electrode layer.

3. The reaction region is arranged so as to include a tapered region whose width increases toward the positive electrode layer from a vertex at a position where the reaction region contacts the outer periphery of the negative electrode layer in a cross-sectional view. The all-solid-state battery according to claim 1 .

4. The all-solid-state battery according to claim 3 , wherein the half apex angle of the tapered region is 45 degrees.

5. 5. The all-solid-state battery according to claim 1, wherein the reaction region is formed by making the concentration of sulfur or carbon higher than that in other portions of the solid electrolyte layer.

6. 5. The all-solid-state battery according to claim 1, wherein the reaction region is formed by impregnating the solid electrolyte layer with an impregnation material made of an ionic liquid.

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