All-solid-state battery

Abstract

An all-solid-state battery (1) is configured by layering a positive electrode current collector (11), a positive electrode active material layer (12), a solid electrolyte layer (14), and a negative electrode body (15) in this order. The positive electrode active material layer (12) includes a flat portion (121) having a uniform thickness and an inclined portion (122) provided on the outer periphery of the flat portion (121) and inclined toward the flat portion (121) away from the positive electrode current collector (11), and comprises an insulating support frame (13) along the outer periphery of the positive electrode active material layer (12) as seen in the stacking direction of the positive electrode current collector (11), the positive electrode active material layer (12), the solid electrolyte layer (14), and the negative electrode body (15). The solid electrolyte layer (14) includes a first portion (141) overlapping the flat portion (121) in the stacking direction, and a second portion (142) overlapping the inclined portion (122) in the stacking direction. The density of the second portion (142) is greater than the density of the first portion (141).

Description

all solid state battery

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

[0002] An all-solid-state battery is a battery in which a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are stacked in this order, or a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, and a negative electrode current collector are stacked in this order (see, for example, Patent Document 1). In the all-solid-state battery described in Patent Document 1, the side surface of the outer periphery of the positive electrode layer is inclined with respect to the layer thickness direction. In addition, an insulating film is provided surrounding the outer periphery of the positive electrode layer, and a solid electrolyte layer is provided covering from the positive electrode layer to a portion of the insulating film.

[0003] JP 2013-182842 A

[0004] In a configuration in which the side surface of the outer periphery of the positive electrode layer is inclined relative to the layer thickness direction, as in Patent Document 1, the displacement of the positive electrode layer at the inclined portion during charging and discharging of the all-solid-state battery is smaller than the displacement of the positive electrode layer at the flat portion. Therefore, shear stress may occur at the boundary between the solid electrolyte layer covering the inclined portion and the solid electrolyte layer covering the flat portion during charging and discharging of the all-solid-state battery, resulting in the formation of cracks. If such cracks occur, cations such as lithium ions may precipitate along the cracks, potentially causing a short circuit between the positive electrode and the negative electrode.

[0005] Furthermore, as described above, during charging and discharging, the solid electrolyte layer covering the portion immediately above the inclined portion and the solid electrolyte layer covering the portion immediately above the flat portion undergo different displacements, so that the density of the solid electrolyte layer covering the portion immediately above the inclined portion is smaller than the density of the solid electrolyte layer covering the portion immediately above the flat portion. In this case, dendrites of deposited metals such as lithium may occur in the low-density portion along the boundary between the solid electrolyte layer covering the portion immediately above the inclined portion and the solid electrolyte layer covering the portion immediately above the flat portion, which may cause a short circuit between the positive electrode and the negative electrode.

[0006] An object of the present invention is to provide an all-solid-state battery that suppresses cracks in the solid electrolyte layer and short circuits caused by dendrites resulting from density differences, thereby suppressing deterioration of battery performance.

[0007] An all-solid-state battery according to one embodiment of the present disclosure is configured by stacking a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode body in this order. The positive electrode active material layer includes a flat portion having a uniform thickness and an inclined portion provided on the outer periphery of the flat portion and inclining toward the flat portion with increasing distance from the positive electrode current collector. An insulating support frame is provided on the outer periphery of the positive electrode active material layer. The solid electrolyte layer includes a first portion overlapping the flat portion in the stacking direction and a second portion overlapping the inclined portion, and the density of the second portion is configured to be greater than the density of the first portion.

[0008] As a result, when the all-solid-state battery is charged and discharged, the density difference between the first portion and the second portion is reduced, which reduces the shear stress generated in the solid electrolyte layer and suppresses the occurrence of cracks. Furthermore, the density difference between the first portion and the second portion is reduced, which also suppresses the occurrence of dendrites. Therefore, short circuits caused by cracks and dendrites can be suppressed, and the deterioration of the battery performance of the all-solid-state battery can be suppressed.

[0009] 1 is a cross-sectional view showing a schematic configuration of an all-solid-state battery according to one embodiment of the present invention. FIG. 2 is a plan view showing a schematic configuration of a power-generating element according to this embodiment. FIG. 3 is a schematic cross-sectional view of the power-generating element taken along line A-A in FIG. 2. FIG. 4 is an enlarged cross-sectional view of a portion of an end portion of the power-generating element according to this embodiment. FIG. 5 is a cross-sectional view showing the state of the end portion of the power-generating element during discharge of the all-solid-state battery of Comparative Example 1. FIG. 6 is a cross-sectional view showing the state of the end portion of the power-generating element during charge of the all-solid-state battery of Comparative Example 1. FIG. 7 is a cross-sectional view showing the state of the end portion of the power-generating element during discharge of the all-solid-state battery of Comparative Example 2. FIG. 8 is a cross-sectional view showing the state of the end portion of the power-generating element during charge of the all-solid-state battery of Comparative Example 2. FIG. 9 is a cross-sectional view showing the state of the end portion of the power-generating element during discharge of the all-solid-state battery in the present embodiment, in which the insulating support frame has lithium ion conductivity. FIG. 10 is a cross-sectional view showing the state of the end portion of the power-generating element during charge of the all-solid-state battery in the present embodiment, in which the insulating support frame does not have lithium ion conductivity. 1 is a cross-sectional view showing the state of an end portion of a power generating element during charging of an all-solid-state battery in a case where the insulating support frame does not have lithium ion conductivity in the present embodiment.

[0010] An all-solid-state battery according to one embodiment of the present invention will now be described. FIG. 1 is a cross-sectional view showing a schematic configuration of an all-solid-state battery 1 according to this embodiment. FIG. 2 is a plan view of the power generating element 2 shown in FIG. 1, and FIG. 3 is a cross-sectional view of the power generating element 2 taken along line A-A in FIG. 2. FIG. 4 is a cross-sectional view showing an enlarged portion of an end portion of the power generating element 2. As shown in FIG. 1, the all-solid-state battery 1 according to this embodiment includes the power generating element 2, electrode tabs 3, and an exterior material 4. The power generating element 2 and the electrode tabs 3 are electrically connected. The exterior material 4 accommodates the power generating element 2 and the electrode tabs 3, with a portion of the electrode tabs 3 extending (exposed) to the outside. The electrode tabs 3 include a positive electrode tab 3A and a negative electrode tab 3B. The direction from the positive electrode tab 3A toward the negative electrode tab 3B is defined as the X direction. 2 and 3, the power generating element 2 includes a positive electrode current collector 11, a positive electrode active material layer 12, an insulating support frame 13, a solid electrolyte layer 14, and a negative electrode body 15 (see FIGS. 3 and 4). The positive electrode current collector 11, the solid electrolyte layer 14, and the negative electrode body 15 are stacked in a Z direction (stacking direction) perpendicular to the X direction. The direction perpendicular to the X direction and the Z direction is defined as a Y direction. The negative electrode body 15 is not shown in FIG. 2.

[0011] The positive electrode current collector 11 is made of a metal material such as aluminum, nickel, iron, stainless steel, titanium, or copper, and is formed in the shape of a rectangular thin plate. Positive electrode active material layers 12 are laminated on the +Z side surface and the −Z side surface of the positive electrode current collector 11, respectively. The positive electrode current collector 11 is connected to the positive electrode tab 3A.

[0012] The positive electrode active material layer 12 is made of a positive electrode active material. Examples of the positive electrode active material that constitutes the positive electrode active material layer 12 include LiMn ２ O ４ , LiCoO ２ , LiNiO ２ , Li(Ni-Mn-Co)O ２Examples of such transition metals include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds, in which a portion of these transition metals has been substituted with another element. While an example in which the positive electrode active material layer 12 uses a lithium compound is shown here, batteries using other metals may also be used. The positive electrode active material layer 12 is formed in a rectangular shape in plan view from the Z direction, and the rectangular outer periphery is located inside the rectangular outer periphery of the positive electrode current collector 11.

[0013] As shown in FIG. 2 , the positive electrode active material layer 12 includes a flat portion 121 that is rectangular in plan view from the Z direction, and an inclined portion 122 that surrounds the outer periphery of the flat portion 121. As shown in FIGS. 3 and 4 , the flat portion 121 has a uniform thickness in the Z direction, and the surface facing the solid electrolyte layer 14 is a flat surface parallel to the XY plane. On the other hand, the surface of the inclined portion 122 facing the solid electrolyte layer 14 is an inclined surface that inclines toward the flat portion 111 as it moves away from the positive electrode current collector 11. The inclined surface of the inclined portion 122 is inclined at an angle of 2° to 45° with respect to the positive electrode current collector 11 (XY plane). Such an angle allows the positive electrode active material layer 12 to be naturally formed during coating, thereby improving manufacturing efficiency.

[0014] The insulating support frame 13 has a rectangular frame shape in a plan view from the Z direction and is provided along the outer periphery of the positive electrode active material layer 12 to surround the positive electrode active material layer 12. In this embodiment, as shown in FIG. 2 , the outer edge of the insulating support frame 13 coincides with the outer edge of the positive electrode current collector 11 or is located between the outer edge of the positive electrode current collector 11 and the edge (outer edge 123) of the inclined portion 122 on the positive electrode current collector 11 side. Also, as shown in FIGS. 2 to 4 , the inner edge of the insulating support frame 13 is located flush with the edge (inner edge 124) of the inclined portion 122 on the flat portion 121 side. Therefore, in this embodiment, the insulating support frame 13 is disposed to cover the inclined portion 122. In an initial state in which the all-solid-state battery 1 is not being charged or discharged, the surface of the insulating support frame 13 on the solid electrolyte layer 14 side is formed flush with the flat portion 121. The insulating support frame 13 is made of a material having electrical insulation properties equivalent to those of the solid electrolyte layer 14, and has an electrical resistivity of 1×10 ５ (Ω cm) or more, preferably 1×10 ６(Ω·cm) or more. This can promote the electrode reaction at the interface between the positive electrode active material layer 12 and the solid electrolyte layer 14.

[0015] The solid electrolyte layer 14 is formed in a rectangular shape in a plan view seen from the Z direction, and is disposed so as to cover the positive electrode active material layer 12 and the insulating support frame 13. Specifically, the outer peripheral edge of the solid electrolyte layer 14 coincides with the outer frame edge of the insulating support frame 13, or is located between the outer frame edge of the insulating support frame 13 and the outer edge 123 of the positive electrode active material layer 12. Therefore, in a plan view seen from the Z direction, the solid electrolyte layer 14 includes a first portion 141 overlapping the flat portion 121 of the positive electrode active material layer 12, a second portion 142 overlapping the inclined portion 122 of the positive electrode active material layer 12, and a third portion 143 that does not overlap with the positive electrode active material layer 12 but overlaps only with the insulating support frame 13.

[0016] The solid electrolyte layer 14 of this embodiment is configured so that, in an initial state when no charge or discharge is being performed, the density of the second portion 142 and the third portion 143 is higher than the density of the first portion 141. As will be described in detail later, the density of the second portion 142 and the third portion 143 is at least 1.05 times the density of the first portion 141, and this configuration suppresses the occurrence of cracks and dendrites in the solid electrolyte layer 14 and the slippage of the outer periphery of the solid electrolyte layer 14.

[0017] Furthermore, the surface roughness of the second portion 142 and the third portion 143 of the solid electrolyte layer 14 on the anode body 15 side is smaller than the surface roughness of the first portion 141 on the anode body 15 side. Therefore, the contact area between the second portion 142 and the third portion 143 and the anode body 15 is smaller than the contact area between the first portion 141 and the anode body 15. For this reason, the amount of lithium deposition in the second portion 142 and the third portion 143 is smaller than the amount of lithium deposition in the first portion 141, and conduction between the positive electrode active material layer 12 and the anode body 15 can be suppressed.

[0018] The anode body 15 is composed of an anode current collector. Alternatively, the anode body 15 may be composed of a laminate of an anode active material layer laminated on the solid electrolyte layer 14 and an anode current collector laminated on the anode active material layer. The anode current collector can be composed of a conductive material such as a thin metal plate, similar to the cathode current collector. The anode current collector is connected to the anode tab 3B. When an anode active material layer is provided, a carbon-based material such as graphite can be used.

[0019] (Suppression of Crack and Dendrite Occurrence in Solid Electrolyte Layer 14) Next, the solid electrolyte layer 14 during charge and discharge in the all-solid-state battery 1 described above will be described. First, the occurrence of cracks and dendrites will be described using the configuration of a comparative example. FIGS. 5 and 6 are diagrams showing a schematic configuration of an end portion of a power-generating element 80 of an all-solid-state battery of Comparative Example 1. FIG. 5 is a cross-sectional view showing the state of the end portion of the power-generating element 80 during discharge, and FIG. 6 is a cross-sectional view showing the state of the end portion of the power-generating element 80 during charge. In FIGS. 5 and 6, the dashed lines indicate the surface position of the positive electrode active material layer 82 in the initial state of the all-solid-state battery, in which no charge or discharge is being performed. In the all-solid-state battery of Comparative Example 1, the power-generating element 80 includes a positive electrode current collector 81, a positive electrode active material layer 82, an insulating support frame 83, a solid electrolyte layer 84, and an anode body 85. Here, in Comparative Example 1, the positive electrode active material layer 82 has a flat portion 821 and an inclined portion 822, similar to the positive electrode active material layer 12 of the present embodiment. The insulating support frame 83 is also assumed to surround the outer periphery of the positive electrode active material layer 82 and extend up to a region overlapping the inclined portion 822. In Comparative Example 1, the insulating support frame 83 is assumed to have lithium ion conductivity.

[0020] In Comparative Example 1, when viewed from the Z direction, the solid electrolyte layer 84 includes a first portion 841 overlapping the flat portion 821, a second portion 842 overlapping the inclined portion 822, and a third portion 843 overlapping the insulating support frame 13 on the outer periphery of the second portion 842. In Comparative Example 1, the first portion 841, the second portion 842, and the third portion 843 are configured to have the same density in the initial state (i.e., the state at the time of manufacture) when no charge or discharge is performed.

[0021] 5 , in the all-solid-state battery of Comparative Example 1, the volume of the positive electrode active material layer 82 increases during discharge. At this time, since the thickness in the Z direction differs between the flat portion 821 and the inclined portion 822, the amount of increase in volume of the flat portion 821 is greater than the amount of change in volume of the inclined portion 822. Therefore, a higher stress is applied to the first portion 841 of the solid electrolyte layer 84 than to the second portion 842, and the first portion 841 has a higher density.

[0022] As shown in FIG. 6 , during charging, the volume of the positive electrode active material layer 82 decreases, and metallic lithium 86 precipitates between the solid electrolyte layer 84 and the negative electrode body 85. In Comparative Example 1, because the insulating support frame 83 has lithium ion conductivity, metallic lithium 86 precipitates also between the second portion 842 and the negative electrode body 85. However, the amount of lithium precipitated in the first portion 841 is greater than the amount of lithium precipitated in the second portion 842. Therefore, the first portion 841 of the solid electrolyte layer 84 is subjected to a higher stress than the second portion 842, resulting in a higher density. Repeated charge and discharge of the all-solid-state battery repeatedly changes the volume of the positive electrode active material layer 82 and the solid electrolyte layer 84. In this case, shear stress is generated due to the density difference between the first portion 841 and the second portion 842 of the solid electrolyte layer 84, increasing the likelihood of cracks occurring near the boundary between the first portion 841 and the second portion 842. If such cracks occur, the deposited lithium may enter the cracks, causing a short circuit between the positive electrode active material layer 82 and the negative electrode body 85 .

[0023] 7 and 8 are enlarged cross-sectional views showing an end of a power-generating element 90 of Comparative Example 2, with FIG. 7 being a cross-sectional view showing the state of the power-generating element 90 during discharge, and FIG. 8 being a cross-sectional view showing the state of the power-generating element 90 during charge. In FIGS. 7 and 8 , the dashed lines indicate the surface position of a positive electrode active material layer 82 in an initial state in which the all-solid-state battery has not been charged or discharged. In the all-solid-state battery of Comparative Example 2, the power-generating element 90 includes a positive electrode current collector 81, a positive electrode active material layer 82, an insulating support frame 93, a solid electrolyte layer 84, and an anode body 85. This all-solid-state battery differs from Comparative Example 1 in that the insulating support frame 93 does not have lithium ion conductivity.

[0024] In the all-solid-state battery of Comparative Example 2, as shown in FIG. 7 , during discharge, the flat portion 821 of the positive electrode active material layer 82 increases in size, but the inclined portion 822 experiences no (or very little) volume change. Therefore, similar to Comparative Example 1, the first portion 841 of the solid electrolyte layer 84 has a higher density than the second portion 842. Furthermore, in Comparative Example 2, the density difference at the boundary between the first portion 841 and the second portion 842 increases. Furthermore, as shown in FIG. 8 , during charge, the volume of the positive electrode active material layer 82 decreases, and metallic lithium 86 precipitates between the solid electrolyte layer 84 and the negative electrode body 85. In Comparative Example 2, the precipitation of metallic lithium 86 between the second portion 842 and the negative electrode body 85 does not occur, or is significantly smaller than in Comparative Example 1. Therefore, due to the precipitation of lithium between the first portion 841 and the negative electrode body 85, the density of the first portion 841 becomes higher than the density of the second portion 842, and the density difference at the boundary between the first portion 841 and the second portion 842 increases.

[0025] Therefore, the density difference between the first portion 841 and the second portion 842 changes sharply across the boundary, causing lithium to precipitate along the boundary portion of the second portion 842, so-called dendrites to form. For this reason, the generation of dendrites may cause a short circuit between the positive electrode active material layer 82 and the negative electrode body 85. Furthermore, as in Comparative Example 1, repeated charge and discharge of the all-solid-state battery repeatedly causes a density difference to repeatedly occur between the first portion 841 and the second portion 842, which increases the possibility of cracks occurring near the boundary between the first portion 841 and the second portion 842.

[0026] Fig. 9 is an enlarged cross-sectional view showing the state of the end of the power-generating element 2 during discharge in this embodiment, and Fig. 10 is an enlarged cross-sectional view showing the state of the end of the power-generating element 2 during charge. In Figs. 9 and 10, the dashed lines indicate the surface position of the positive electrode active material layer 12 in the initial state when the all-solid-state battery is not being charged or discharged. The examples in Figs. 9 and 10 also show an example in which the insulating support frame 13 has lithium ion conductivity. In contrast to Comparative Example 1 described above, in the all-solid-state battery 1 of this embodiment, the densities of the second portion 142 and the third portion 143 are at least 1.05 times the density of the first portion 141 in the initial state when no charge or discharge is being performed.

[0027] In this embodiment, as shown in FIG. 9 , during discharge, similar to Comparative Example 1, the volumes of the flat portion 121 and the inclined portion 122 of the positive electrode active material layer 12 increase, and the increase in volume of the flat portion 121 is greater than the change in volume of the inclined portion 122. Therefore, the first portion 141 of the solid electrolyte layer 14 is compressed relative to the second portion 142, and its volume decreases. Furthermore, as shown in FIG. 10 , during charge, similar to Comparative Example 1, the volume of the positive electrode active material layer 12 decreases, and metallic lithium 16 precipitates between the solid electrolyte layer 14 and the negative electrode body 15. At this time, the amount of lithium precipitated in the first portion 841 becomes greater than the amount of lithium precipitated in the second portion 842.

[0028] For example, the volume change rate (compression rate) of the first portion 141 during charging and discharging of the all-solid-state battery 1 is 85% to 95% compared to the initial state (the position of the dashed line), and the volume change rate of the second portion 142 is 95% to 98% compared to the initial state. Therefore, the compression rate of the first portion 141 is higher than that of the second portion 142. However, in this embodiment, in the initial state (as manufactured) before charging or discharging, the density of the second portion 142 is higher than the density of the first portion 141, at least 1.05 times and 1.2 times higher. In this case, the density difference between the first portion 141 and the second portion 142 after the volume change described above is reduced, thereby suppressing the occurrence of cracks during charging and discharging. Note that if the density of the second portion 142 is less than 1.05 times the density of the first portion 141, the density difference between the first portion 141 and the second portion 142 during charging and discharging becomes large. In this case, the above effect becomes insufficient, and the rate of crack occurrence increases compared to when the density of the second portion 142 is 1.05 times the density of the first portion 141. Even in this case, the difference in density between the first portion 141 and the second portion 142 is smaller than in Comparative Example 1 and Comparative Example 2, and therefore the occurrence of cracks is suppressed compared to Comparative Example 1 and Comparative Example 2. Furthermore, the density of the second portion 142 may be more than 1.2 times the density of the first portion 141, but it is difficult to achieve a density more than 1.2 times in manufacturing.

[0029] The above describes a case where the insulating support frame 13 has lithium ion conductivity, but the insulating support frame 13 does not have to have lithium ion conductivity. Figures 11 and 12 are enlarged cross-sectional views showing the power generating element 2 during charge and discharge when the insulating support frame 13 without lithium ion conductivity is used in this embodiment. Figure 11 shows the state of the end of the power generating element 2 during discharge, and Figure 12 shows the state of the end of the power generating element 2 during charge. In Figures 11 and 12, the dashed lines indicate the surface position of the positive electrode active material layer 12 in the initial state of the all-solid-state battery 1, when no charge or discharge has been performed.

[0030] In this embodiment, when the insulating support frame 13 does not have lithium ion conductivity, as shown in FIG. 11 , during discharge, the volume of the flat portion 121 increases, and the increase in volume of the flat portion 121 is greater than the change in volume of the inclined portion 122, as in Comparative Example 2. Therefore, the first portion 141 of the solid electrolyte layer 14 is compressed relative to the second portion 142, and its volume decreases. Furthermore, as shown in FIG. 12 , during charge, the volume of the positive electrode active material layer 12 decreases, and metallic lithium 16 precipitates between the solid electrolyte layer 14 and the negative electrode body 15. However, even if the first portion 141 is compressed during charge, the density of the second portion 142 is initially high, so the difference in density between the first portion 141 and the second portion 142 is small, and the generation of dendrites can be suppressed.

[0031] Furthermore, in the present embodiment, the density of the third portion 143 is also greater than the density of the first portion 141, similar to the density of the second portion 142. With this configuration, the problem of the solid electrolyte layer 14 sliding off from the outer periphery of the third portion 143 can be suppressed compared to when the density of the third portion 143 is low.

[0032] [Effects of the Present Embodiment] The all-solid-state battery 1 of the present embodiment includes a power generating element 2 configured by laminating a positive electrode current collector 11, a positive electrode active material layer 12, a solid electrolyte layer 14, and a negative electrode body 15 in this order. The positive electrode active material layer 12 includes a flat portion 121 having a uniform thickness and an inclined portion 122 provided on the outer periphery of the flat portion 121 and inclined toward the flat portion 121 with increasing distance from the positive electrode current collector 11. The power generating element 2 of the all-solid-state battery 1 also includes an insulating support frame 13 provided along the outer periphery of the positive electrode active material layer 12 when viewed from the Z direction. The solid electrolyte layer 14 includes a first portion 141 overlapping with the flat portion 121 in the Z direction and a second portion 142 overlapping with the inclined portion 122 in the Z direction, and the density of the second portion 142 is greater than the density of the first portion 141.

[0033] In such an all-solid-state battery 1, when the solid electrolyte layer 14 is compressed and its volume is reduced during charging and discharging, the density difference between the first portion 141 and the second portion 142 is reduced. This reduces the occurrence of cracks due to shear stress and dendrites at the boundary where the density difference changes abruptly. This prevents a decrease in the battery performance of the all-solid-state battery 1.

[0034] In this embodiment, the solid electrolyte layer 14 further includes a third portion 143 that overlaps the insulating support frame 13 in the Z direction outside the second portion 142, and the third portion 143 has a density greater than that of the first portion 141. Having such a high-density third portion 143 on the outer periphery of the solid electrolyte layer 14 can prevent the solid electrolyte layer from sliding off.

[0035] In this embodiment, the density of the second portion 142 is 1.05 times or more the density of the first portion 141. If the density of the second portion is less than 1.05 times the density of the first portion 141, the density difference between the first portion 141 and the second portion 142 cannot be made sufficiently small during charging and discharging of the all-solid-state battery 1. In this case, the effect of suppressing the occurrence of cracks and dendrites as described above is reduced. In contrast, by making the density of the second portion 142 1.05 times or more, the occurrence of cracks and dendrites can be more effectively suppressed.

[0036] In this embodiment, the inclined portion 122 of the positive electrode active material layer 12 is provided to surround the outer periphery of the flat portion 121, and the second portion 142 of the solid electrolyte layer 14 is provided to surround the outer periphery of the first portion 141. In the solid electrolyte layer 14, the second portion 142 formed to be denser than the first portion 141 may be formed on only one side of the rectangular solid electrolyte layer 14. Even in this case, compared to configurations without a high-density region such as Comparative Example 1 and Comparative Example 2, the provision of the second portion 142 as a high-density region can suppress the occurrence of cracks and dendrites in the second portion 142, thereby suppressing a decrease in battery performance. In this embodiment, the second portion 142, which is denser than the first portion 141, is further configured to surround the first portion 141. In other words, the second portion 142 denser than the first portion 141 is arranged on all four sides of the rectangular solid electrolyte layer 14. This makes it possible to suppress the occurrence of cracks and dendrites in the entire second portion 142 directly above the inclined portion 122, and more effectively suppress the deterioration of battery performance.

[0037] In this embodiment, the inclination angle of the inclined portion 122 with respect to the positive electrode current collector 11 is 2° to 45°. The inclined portion 122 with such an angle can be easily formed in the process of coating the positive electrode active material layer 12 onto the positive electrode current collector 11 during the production of the positive electrode active material layer 12, thereby reducing the production cost.

[0038] In the present embodiment, the surface roughness of the surface of the second portion 142 facing the anode body 15 is smaller than the surface roughness of the surface of the first portion 141 facing the anode body 15. With this configuration, the contact area between the second portion 142 and the anode body 15 can be made smaller than the contact area between the first portion 141 and the anode body 15. This makes it possible to suppress deposition of lithium between the second portion 142 and the anode body 15, and to suppress a short circuit between the positive electrode active material layer 12 and the anode body 15 due to the deposited lithium.

[0039] In this embodiment, the insulating support frame 13 is 1×10 ５ The positive electrode active material layer 12 has an electrical resistivity of Ω·cm or more, which can prevent short circuits between the positive electrode active material layer 12 and the negative electrode body 15, thereby maintaining the battery performance.

[0040] [Modifications] The present invention is not limited to the above-described embodiment, and includes the following modifications within the scope of achieving the object of the present invention.

[0041] [Variation 1] In the above embodiment, the insulating support frame 13 covers the inclined portion 122 of the positive electrode active material layer 12, but this is not limiting. FIG. 13 is a schematic cross-sectional view of an end portion of a power generating element 2A of an all-solid-state battery according to Variation 1. For example, as shown in FIG. 13, the insulating support frame 13A may not cover the inclined portion 122 of the positive electrode active material layer 12, and the inner edge of the frame of the insulating support frame 13A may be located on the outer edge 123 of the positive electrode active material layer 12. In this case, the second portion 142 of the solid electrolyte layer 14 fills the inclined portion 122 of the positive electrode active material layer 12 up to the surface and is in surface contact with the inclined portion 122. Even with this configuration, the second portion 142 (and the third portion 143) are configured to be denser than the first portion 141, thereby achieving the same effects as the above embodiment and suppressing the occurrence of cracks and dendrites in the solid electrolyte layer 14.

[0042] [Variation 2] In the above embodiment, the positive electrode active material layer 12 has the inclined portion 122 formed along the outer periphery of the flat portion 121, and the entire second portion 142 of the solid electrolyte layer 14 overlapping the inclined portion 122 in the Z direction has a higher density than the first portion 141. In contrast, at least a portion of the second portion 142, for example, only the second portion 142 on one side of the rectangular first portion 141, may be configured to have a higher density than the first portion 141. Even with this configuration, compared to when the entire second portion 142 has the same density as the first portion 141, it is possible to suppress the occurrence of cracks and dendrites in the second portion 142 formed at a higher density, thereby suppressing a decrease in battery performance.

[0043] [Variation 3] In the above embodiment, the third portion 143 of the solid electrolyte layer 14 is formed with a higher density than the first portion 141, thereby preventing the outer periphery of the solid electrolyte layer 14 from sliding off. Alternatively, the third portion 143 may be formed with the same density as the first portion 141. Even in this case, the density of the second portion 142 is greater than the density of the first portion 141, thereby preventing cracks and dendrites from forming in the solid electrolyte layer 14 and reducing deterioration in battery performance. Alternatively, the insulating support frame 13 may be thicker in the Z direction so that it contacts both the positive electrode current collector 11 and the negative electrode body 15, i.e., the outer periphery of the solid electrolyte layer 14 is surrounded by the insulating support frame 13. In this case, the outer periphery (third portion 143) of the solid electrolyte layer 14 is pressed by the insulating support frame 13, thereby preventing the solid electrolyte layer 14 from sliding off.

[0044] [Variation 4] In the above embodiment, an example was shown in which the density of the second portion 142 was at least 1.05 times and 1.2 times that of the first portion 141, but this is not limiting. In the all-solid-state battery 1, the density of the second portion 142 can be appropriately selected depending on the types of the positive electrode active material layer 12, the solid electrolyte layer 14, the anode body 15, and the like. That is, it is sufficient that the density of the first portion 141 and the density of the second portion 142 are equivalent when the all-solid-state battery 1 is charged and discharged. Here, "equivalent" includes not only that the densities of the first portion 141 and the second portion 142 are the same during charging and discharging, but also that the difference in density between the first portion 141 and the second portion 142 is within a predetermined allowable value that can sufficiently suppress the occurrence of cracks and dendrites.

[0045] [Variation 5] In the above embodiment, the angle of the inclined portion 122 is 2° to 45°, but is not limited thereto. Even if the angle of the inclined portion 122 deviates from the above angles, the density of the second portion 142 of the solid electrolyte layer 14 is greater than the density of the first portion 141, and therefore, the same effects as those of the above embodiment can be achieved, and the occurrence of cracks and dendrites can be suppressed, thereby suppressing a decrease in battery performance.

[0046] [Variation 6] In the above embodiment, an example has been shown in which the surface roughness of the second portion 142 facing the anode body 15 is smaller than the surface roughness of the first portion 141 facing the anode body 15, but the present invention is not limited to this. For example, the surface roughness of the second portion 142 and the first portion 141 facing the anode body 15 may be the same. Even in this case, the density of the second portion 142 of the solid electrolyte layer 14 is greater than the density of the first portion 141, thereby achieving the same effects as in the above embodiment, making it possible to suppress the occurrence of cracks and dendrites, and thereby suppressing a decrease in battery performance.

[0047] [Modification 7] In the above embodiment, the electrical resistivity of the insulating support frame 13 is set to 1×10 ５ (Ω cm) is given as an example, but is not limited to this. As long as the insulation between the positive electrode current collector 11 and the negative electrode body 15 and the insulation between the positive electrode active material layer 12 and the negative electrode body 15 are sufficient, the insulation is not limited to the above value.

[0048] DESCRIPTION OF SYMBOLS 1... All-solid-state battery, 2, 2A... Power generation element, 11... Positive electrode current collector, 12... Positive electrode active material layer, 13, 13A... Insulating support frame, 14... Solid electrolyte layer, 15... Negative electrode body, 1 DESCRIPTION OF SYMBOLS 11... Flat part, 121... Flat part, 122... Inclined part, 123... Outer edge, 124... Inner edge, 141... First part, 142... Second part, 143... Third part.

Claims

1. An all-solid-state battery in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, and a negative electrode body are laminated in this order, wherein the positive electrode active material layer includes a flat portion having a uniform thickness and a sloping portion provided on the outer periphery of the flat portion and sloping toward the flat portion with increasing distance from the positive electrode current collector, and an insulating support frame is provided along the outer periphery of the positive electrode active material layer when viewed in the stacking direction of the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode body, and the solid electrolyte layer includes a first portion overlapping the flat portion in the stacking direction and a second portion overlapping the sloping portion in the stacking direction, and the density of the second portion is greater than the density of the first portion.

2. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer further includes a third portion that is outside the second portion and overlaps the insulating support frame in the stacking direction, and the third portion has a density greater than that of the first portion.

3. The all-solid-state battery according to claim 1, wherein the density of the second portion is 1.05 times or more the density of the first portion.

4. The all-solid-state battery according to claim 1, wherein in the positive electrode active material layer, the inclined portion is provided so as to surround the outer periphery of the flat portion, and in the solid electrolyte layer, the second portion is provided so as to surround the outer periphery of the first portion, and the entire second portion surrounding the first portion has a higher density than the first portion.

5. The all-solid-state battery according to claim 1, wherein the inclined portion has an inclination angle of 2° to 45° with respect to the positive electrode current collector.

6. The all-solid-state battery according to claim 1, wherein the surface roughness of the surface of the second portion facing the anode body is smaller than the surface roughness of the surface of the first portion facing the anode body.

7. The insulating support frame is 1 x 10 ５ The all-solid-state battery according to claim 1 , having an electrical resistivity of Ω cm or more.

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