All-solid-state battery

Abstract

To provide an all-solid battery with improved durability by reducing damage to a power generation element during charging and discharging.SOLUTION: In an all-solid battery 100 (single cell 9) according to the present invention, a power generation element portion 1 in which a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 are laminated is arranged, and an insulating member 4 is arranged so as to cover the outer periphery of the power generation element portion 1, the insulating member 4 includes a laminated structure of an insulating layer 41 having an elastic modulus of 5 Gpa or less and an expansion absorption layer 42 having an elastic modulus lower than that of the insulating layer 41 and the stacking direction of the insulating member 4 is the same as that of the power generation element portion 1.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an all-solid-state battery in which the side surface of a power generation element portion laminated in the order of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is covered with an insulating layer, and the insulating layer is formed by a first insulating layer covering the side surface and a second insulating layer covering the side surface of the first insulating layer, and the elastic modulus of the first insulating layer is lower than the elastic modulus of the second insulating layer.

[0003] In Patent Document 1, the first insulating layer having a low elastic modulus suppresses the occurrence of its own cracks by absorbing the volume change due to charge and discharge of the all-solid-state battery, and the second insulating layer having a high elastic modulus protects the first insulating layer and the power generation element portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, the insulating layer is formed of the same material from the positive electrode side to the negative electrode side. On the other hand, during charge and discharge of the all-solid-state battery, since the volume change rates of the positive electrode and the negative electrode are different, a physical load (strain) is applied to either the positive electrode or the negative electrode from the insulating layer, which has an adverse effect on the durability performance.

[0006] An object of the present invention is to provide an all-solid-state battery with improved durability performance by reducing damage to the power generation element portion during charge and discharge.

Means for Solving the Problems

[0007] The all-solid-state battery according to the present invention has a power generation element portion in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated, and further, the So as to closely adhere to and surround the side surface In the all-solid-state battery in which an insulating member is disposed, the insulating member has a laminated structure of an insulating layer having an elastic modulus of 5 GPa or less and an expansion absorption layer having a lower elastic modulus than the insulating layer, and is in the same lamination direction as the power generation element portion. The power generation element portion and the insulating member are arranged between a pair of current collectors. The insulating layer and the expansion absorption layer are laminated in the direction in which the pair of current collectors face each other and are in close contact with the power generation element portion. The negative electrode layer contains lithium metal or a lithium compound. The expansion absorption layer is adjacent to the current collector adjacent to the negative electrode layer among the pair of current collectors, and is adjacent to the negative electrode layer and the solid electrolyte layer and is thicker than the total thickness of the negative electrode layer and the solid electrolyte layer. The insulating layer is adjacent to the positive electrode layer and is thinner than the positive electrode layer. The insulating layer and the expansion absorption layer are joined to each other. The side surfaces of the negative electrode layer and the solid electrolyte layer are each sealed by the expansion absorption layer and are not exposed to the outside. The side surface of the positive electrode layer is not exposed to the outside by being sealed by the expansion absorption layer and the insulating layer .

Advantages of the Invention

[0008] According to the present invention, it is possible to non-uniformly change the volume change rate of the insulating member so as to follow the volume change rate of the positive electrode layer and the volume change rate of the negative electrode layer during charge and discharge, respectively. Therefore, the shape retention of the entire all-solid-state battery during charge and discharge is improved, and the all-solid-state battery has reduced damage to the power generation element portion by the insulating member and enhanced durability performance.

Brief Description of the Drawings

[0009]

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MODE FOR CARRYING OUT THE INVENTION

[0010] [Overview of the Present Embodiment] The all-solid-state battery 100 according to the present embodiment will be described.

[0011] FIG. 1 is a schematic diagram (cross-sectional view) for explaining a single cell 9 included in the all-solid-state battery 100 of the first embodiment. The left side of the one-dot chain line in the center shows the single cell 9 before charging, and the right side of the one-dot chain line in the center shows the single cell 9 after charging.

[0012] The all-solid-state battery 100 of the present embodiment is a secondary battery capable of being charged and discharged a plurality of times. The all-solid-state battery 100 is a so-called laminated all-solid-state battery 100 that houses, in a sealed state with a laminate layer (not shown), which is a battery exterior material, a structure (not shown) in which a plurality of single cells 9 described below are laminated. By adopting a laminated type, the battery can be made compact and have a high capacity.

[0013] However, the single cell 9 accommodated 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 it may be a single layer. Note that the single cell 9 is formed in a sheet shape such as a circular or rectangular shape, for example, in a state before being accommodated in the battery exterior material. In addition, the appearance of the all-solid-state battery 100 of the present embodiment and the electrical connection state (electrode structure) inside are not particularly limited.

[0014] The appearance of the all-solid-state battery 100 can be a circle, an ellipse, or a rectangular shape in a plan view. Alternatively, it may be a cylindrical shape that accommodates a single layer or a plurality of single cells 9 wound around. In addition, as the electrode structure of the all-solid-state battery 100, either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type) may be adopted. That is, the aspects of the all-solid-state battery 100 other than the configuration of the single cell 9 described below are not particularly limited, regardless of whether they are known or unknown.

[0015] The single cell 9 has a configuration in which a power generation element portion 1 formed by laminating a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 in this order is sandwiched between a pair of current collectors (negative electrode current collector 3 and positive electrode current collector 2) facing each other. In the single cell 9, an insulating member 4 is disposed so as to cover the periphery of the power generation element portion 1 (positive electrode layer 11, solid electrolyte layer 12, negative electrode layer 13) between the pair of current collectors (negative electrode current collector 3 and positive electrode current collector 2).

[0016] The positive electrode current collector 2 is a thin plate formed of a metal such as aluminum (Al). The negative electrode current collector 3 is a thin plate formed of a metal such as stainless steel (SUS) or copper (Cu).

[0017] The positive electrode layer 11 is formed on the surface of the positive electrode current collector 2 facing the negative electrode current collector 3. The positive electrode layer 11 is preferably formed using, for example, NMC811 (lithium nickel cobalt manganese oxide) as the main raw material. Further, the positive electrode layer 11 preferably contains a positive electrode active material containing sulfur. The type of the positive electrode active material containing sulfur is not particularly limited, and examples thereof include elemental sulfur (S), particles or thin films of organic sulfur compounds or inorganic sulfur compounds, and any material that can release lithium ions during charging and occlude lithium ions during discharging by utilizing the redox reaction of sulfur. Note that the volume (thickness) of the positive electrode layer 11 decreases by about 10% during charging.

[0018] The solid electrolyte layer 12 is a layer containing a solid electrolyte as a main component and interposed between the negative electrode layer 13 and the positive electrode layer 11. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and a sulfide solid electrolyte is preferred, such as argyrodite (Li6PS5Cl).

[0019] The negative electrode layer 13 is disposed on the surface of the negative electrode current collector 3 facing the positive electrode current collector 2 and is composed of a negative electrode active material containing a lithium alloy or lithium metal. Further, the same material as the negative electrode current collector 3 can be applied to the negative electrode layer 13. When the single cell 9 is charged, lithium metal is deposited (about 10 μm in thickness) on the negative electrode layer 13, and when discharged, the deposited lithium metal disappears. When lithium metal is applied as the negative electrode layer 13, the lithium metal itself becomes ions and reciprocates between the positive electrode layer 11, so the amount of expansion and contraction accompanying charge and discharge is larger than when other materials for the negative electrode are applied.

[0020] The negative electrode layer 13 can be applied with one containing a negative electrode active material containing a lithium compound or the like. The type of the negative electrode active material is not particularly limited, and examples thereof include carbon materials, metal oxides, and metal active materials. Examples of the carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented pyrolytic graphite (HOPG), hard carbon, soft carbon, and the like. Examples of the metal oxides include, for example, Nb2O5, Li4Ti5O 12Examples include the above. Further, a silicon-based negative electrode active material or a tin-based negative electrode active material may be used. Here, silicon and tin belong to Group 14 elements and are known to be negative electrode active materials that can greatly improve the capacity of a non-aqueous electrolyte secondary battery. Since these simple substances can occlude and release a large number of charge carriers (such as lithium ions) per unit volume (mass), they become high-capacity negative electrode active materials. Here, as the silicon-based negative electrode active material, it is preferable to use Si simple substance. Similarly, it is also preferable to use silicon oxides such as SiO x (0.3 ≦ x ≦ 1.6). At this time, the range of x is more preferably 0.5 ≦ x ≦ 1.5, and even more preferably 0.7 ≦ x ≦ 1.2. Further, an alloy containing silicon (silicon-containing alloy-based negative electrode active material) may be used. On the other hand, examples of the negative electrode active material containing tin element (tin-based negative electrode active material) include Sn simple substance, tin alloys (Cu-Sn alloy, Co-Sn alloy), amorphous tin oxide, tin silicon oxide, etc. Among these, examples of the amorphous tin oxide include SnB 0.4 P 0.6 O 3.1 is exemplified. Also, an example of the tin silicon oxide is SnSiO3. Further, as the negative electrode active material, a metal containing lithium may be used. Such a negative electrode active material is not particularly limited as long as it is an active material containing lithium, and examples include metallic lithium and lithium-containing alloys. Examples of the lithium-containing alloy include an alloy of Li and 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, it is also possible to use negative electrode active materials other than the above. The present invention exhibits particularly excellent effects when the expansion and contraction of the negative electrode active material during charge and discharge are large. From such a viewpoint and the point of high capacity, the negative electrode active material preferably contains metallic lithium, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably contains metallic lithium.

[0021] The content of the negative electrode active material in the negative electrode layer 13 is not particularly limited, but for example, it is preferably in the range of 40 to 99% by mass, and more preferably in the range of 50 to 90% by mass.

[0022] The negative electrode layer 13 preferably further contains a solid electrolyte. By including a solid electrolyte in the negative electrode layer 13, the ionic conductivity of the negative electrode layer 13 can be improved. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, but a sulfide solid electrolyte is preferred.

[0023] Examples of the sulfide solid electrolyte 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-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is any one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In), etc. It should be noted that the description of "Li2S-P2S5" means a sulfide solid electrolyte formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0024] The sulfide solid electrolyte may have, for example, a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of the sulfide solid electrolyte having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Further, examples of the sulfide solid electrolyte having a Li4P2S7 skeleton include a Li-P-S-based solid electrolyte called LPS (for example, Li7P3S 11 ). Further, as the sulfide solid electrolyte, for example, LGPS represented by Li (4-x) Ge (1-x) P x S4 (where x satisfies 0 < x < 1) may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing a P element, and more preferably a material mainly composed of Li2S-P2S5. Further, the sulfide solid electrolyte may contain a halogen (F, Cl, Br, I).

[0025] Further, when the sulfide solid electrolyte is a Li2S-P2S5 system, the ratio of Li2S and P2S5 is preferably in 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.

[0026] As described above, during charging of the single cell 9, the thickness of the negative electrode layer 13 increases while the thickness of the positive electrode layer 11 decreases, and during discharging of the single cell 9, the thickness of the negative electrode layer 13 decreases while the thickness of the positive electrode layer 11 increases. In FIG. 1 (and FIG. 2), the power generation element portion 1 increases in thickness by charging and decreases in thickness by discharging. However, the overall thickness of the power generation element portion 1 may decrease during charging depending on the materials of the positive electrode layer 11 and the negative electrode layer 13 and the setting of their thicknesses.

[0027] The insulating member 4 is formed of an insulating material such as resin, and is arranged so as to be in close contact (bonded) with the side surface of the power generation element portion 1 and to have a frame shape (ring shape) in plan view so as to surround it. The insulating member 4 has a laminated structure of an insulating layer 41 and an expansion absorption layer 42, and has the same lamination direction as the power generation element portion 1.

[0028] The insulating layer 41 is arranged in a manner adjacent (joined) to the positive current collector 2, is thicker than the positive electrode layer 11, and is set to be thinner than the sum of the thicknesses of the positive electrode layer 11 and the solid electrolyte layer 12.

[0029] The expansion absorption layer 42 is arranged in a manner adjacent (joined) to the negative current collector 3, is thicker than the negative electrode layer 13, and is set to be thinner than the sum of the thicknesses of the negative electrode layer 13 and the solid electrolyte layer 12.

[0030] The elastic modulus (Young's modulus) of the insulating layer 41 and the expansion absorption layer 42 is 5 GPa or less (the elastic modulus of the negative electrode layer 13 (lithium metal)), and further, the elastic modulus of the expansion absorption layer 42 is set to be lower than the elastic modulus of the insulating layer 41.

[0031] Here, for example, polyimide (e.g., Kapton (registered trademark): 3.3 GPa) is applied as the insulating layer 41, and PTFE (polytetrafluoroethylene: 0.5 GPa) is applied as the expansion absorption layer 42.

[0032] As the adhesive (not shown) used for joining the insulating layer 41 and the positive current collector 2, joining the expansion absorption layer 42 and the negative current collector 3, and joining the insulating layer 41 and the expansion absorption layer 42, for example, acrylic-modified silicone resin-based elastic adhesives (e.g., Super X (registered trademark) No. 8008, Super XG No. 777, SX720W manufactured by Cemedine Co., Ltd.), two-component mixed-curing epoxy-modified silicone resin-based elastic adhesives (e.g., EP001K manufactured by Cemedine Co., Ltd.) and other resin-based adhesives, and other thermosetting resins such as epoxy resins or silicone resins are applied.

[0033] [Manufacturing process of single cell 9] As a manufacturing process of the single battery 9, an aluminum foil (positive electrode current collector 2), NMC811 (positive electrode layer 11), all-dielectric (solid electrolyte layer 12), and a stainless-steel foil (negative electrode layer 13 and negative electrode current collector 3) are laminated in this order. Also, between the aluminum foil (positive electrode current collector 2) and the stainless-steel foil (negative electrode layer 13), a Kapton (registered trademark) (insulating layer 41) and a PTFE (expansion absorption layer 42) are laminated in this order so as to go around the outer periphery of the NMC811 (positive electrode layer 11) and the all-dielectric (solid electrolyte layer 12), and then pressed and molded in the lamination direction.

[0034] [Comparison between the First Embodiment and the First Comparative Example] FIG. 2 is a schematic diagram (cross-sectional view) for explaining the single battery 9W included in the all-solid-state battery 100W of the first comparative example. The left side of the one-dot chain line in the center shows the single battery 9W before charging, and the right side of the one-dot chain line in the center shows the single battery 9W after charging.

[0035] The all-solid-state battery 100W (single battery 9W) of the first comparative example has substantially the same structure as the all-solid-state battery 100 (single battery 9) of the first embodiment, but the insulating member 4 is formed of a single insulating material. As the insulating member 4, one having an elastic modulus lower than that of, for example, the negative electrode layer 13 (lithium metal) is applied.

[0036] When charging and discharging are performed in the single battery 9 and the single battery 9W, the volume (thickness) changes in the negative electrode layer 13 and the positive electrode layer 11. At this time, the insulating member 4 can change its thickness following the change in the volume (thickness) of the negative electrode layer 13 and the positive electrode layer 11.

[0037] However, in the power generation element unit 1, when charging, the lithium metal in the positive electrode layer 11 moves to the negative electrode layer 13 side, so that the thickness of the negative electrode layer 13 increases and the thickness of the positive electrode layer 11 decreases. Conversely, when discharging, the lithium metal moves to the positive electrode layer 11 side, so that the thickness of the negative electrode layer 13 decreases and the thickness of the positive electrode layer 11 increases. Therefore, in the power generation element unit 1, expansion and contraction in the thickness direction occur unevenly during charging and discharging of the single battery 9W (single battery 9).

[0038] In particular, when lithium metal is applied as the negative electrode layer 13, the volume change rate (thickness change rate) of the negative electrode layer 13 becomes significant, so the non-uniformity of the expansion and contraction in the thickness direction during charge and discharge of the power generation element unit 1 becomes even more significant.

[0039] On the other hand, the insulating member 4 receives non-uniform stress from the power generation element unit 1 along with the non-uniform expansion and contraction, but is formed of a single material. For this reason, in the insulating member 4, a stress (restoring force) that attempts to make the stress uniform inside the insulating member 4 with respect to the non-uniform stress is generated, and this stress is applied to the power generation element unit 1. Therefore, since the stress from the insulating member 4 is always applied to either the positive electrode layer 11 or the negative electrode layer 13, the durability of the power generation element unit 1 decreases. In this case, the power generation element unit 1 peels off from the insulating member 4, lithium metal (lithium dendrite) is deposited on the side surface of the power generation element unit 1 during charge and discharge, and the lithium metal shorts the negative electrode layer 13 and the positive electrode layer 11.

[0040] On the other hand, as shown in FIG. 1, in the all-solid-state battery 100 (single cell 9) of the first embodiment, the insulating member 4 is divided into an insulating layer 41 and an expansion absorption layer 42 in the thickness direction. The insulating layer 41 is joined to the positive electrode layer 11, and the expansion absorption layer 42 is joined to the negative electrode layer 13. Further, the elastic modulus of the insulating layer 41 and the expansion absorption layer 42 is set to 5 GPa or less (equal to or less than the elastic modulus of the negative electrode layer 13 (lithium metal)), and in particular, the elastic modulus of the expansion absorption layer 42 is set lower than the elastic modulus of the insulating layer 41.

[0041] Thereby, the insulating layer 41 can expand and contract following the expansion and contraction of the positive electrode layer 11, and the expansion absorption layer 42 can also expand and contract following the expansion and contraction of the negative electrode layer 13, so the stress applied from the insulating member 4 to the positive electrode layer 11 and the negative electrode layer 13 can be reduced.

[0042] As described above, since the volume change rate of the negative electrode layer 13 is larger than that of the positive electrode layer 11, the stress applied by the negative electrode layer 13 to the expansion absorption layer 42 and the stress (restoring force) applied from the expansion absorption layer 42 to the negative electrode layer 13 increase. However, by setting the elastic modulus of the expansion absorption layer 42 to be smaller than that of the insulating layer 41, the stress (restoring force) applied from the expansion absorption layer 42 to the negative electrode layer 13 can be reduced, and accordingly, the durability of the negative electrode layer 13 can be enhanced.

[0043] Therefore, it becomes possible to non-uniformly change the volume change rate of the insulating member 4 so as to follow the volume change rates of the positive electrode layer 11 and the negative electrode layer 13 during charge and discharge, respectively. Thus, damage to the power generation element unit 1 can be reduced and the durability performance can be enhanced.

[0044] Furthermore, the insulating layer 41 and the expansion absorption layer 42 are joined to each other, and the elastic modulus of the insulating layer 41 is set to 5 GPa or less (the elastic modulus of the negative electrode layer 13 (lithium metal)). Thereby, the insulating layer 41 can expand and contract following the expansion and contraction of the negative electrode layer 13 to some extent. Accordingly, the durability of the expansion absorption layer 42 can be enhanced by reducing the amount of expansion and contraction of the expansion absorption layer 42.

[0045] [Number of charge-discharge cycles and discharge capacity] FIG. 3 is a diagram showing the relationship between the number of charge-discharge cycles and the discharge capacity per unit mass of the all-solid-state battery 100 (single cell 9) of the first embodiment. FIG. 4 is a diagram showing the relationship between the number of charge-discharge cycles and the discharge capacity per unit mass of the all-solid-state battery 100W (single cell 9W) of the first comparative example.

[0046] The inventor of the present application examined the changes in the discharge capacity of the single cell 9 of the first embodiment and the single cell 9W of the first comparative example when charge and discharge were repeated. For the single cell 9 and the single cell 9W, the C rate was set to 0.05 (the rate at which full discharge is achieved in 20 hours), and constant current charging and constant current discharging were repeated, and charge and discharge were repeated between a voltage of 4.3 [V] (starting discharge voltage) and 2.5 [V] (ending voltage).

[0047] In the single battery 9 of the first embodiment, the ambient temperature was set to room temperature (25 [°C]) and 60 [°C], and the discharge capacity was calculated while repeating charge and discharge at each temperature.

[0048] When the ambient temperature is room temperature (25 [°C]), the discharge capacity is calculated to be approximately 165 [mAh / g] in the first charge and discharge. However, the value of the discharge capacity monotonically decreases as the charge and discharge are repeated. This is because as the charge and discharge are repeated, the amount of lithium ions moving during charge and discharge trapped in the positive electrode layer 11 or the negative electrode layer 13 increases, and the discharge capacity decreases accordingly. Also, although the discharge capacity monotonically decreases, it is about 120 [mAh / g] even after repeating the charge and discharge 14 times, indicating that no short circuit has occurred in the single battery 9.

[0049] When the ambient temperature is 60 [°C], the discharge capacity is approximately 185 [mAh / g] in the first charge and discharge, which is higher than that at room temperature (25 [°C]). This is due to the fact that as the temperature rises, the internal resistance of the entire single battery 9 decreases. And although the discharge capacity decreases as the charge and discharge are repeated, it is about 136 [mAh / g] even after performing the charge and discharge 9 times, indicating that no short circuit has occurred.

[0050] In the single battery 9W of the first comparative example, the ambient temperature was set to room temperature (25 [°C]), and the discharge capacity was calculated while repeating charge and discharge at each temperature.

[0051] Although it had a discharge capacity of approximately 157 [mAh / g] in the first charge and discharge, the discharge capacity decreased rapidly to approximately 130 [mAh / g] in the second charge and discharge, and became 0 [mAh / g] in the third charge and discharge. This is considered to be due to the short circuit of the single battery 9W for the above reasons. In the single battery 9W, when the elastic modulus of the insulating member 4 is formed of a material with a value greater than 5 GPa, it also short-circuits after two or three charge and discharges.

[0052] [Second Comparative Example] FIG. 5 is a schematic diagram (cross-sectional view) for explaining a single cell 9X included in the all-solid-state battery 100X of the second comparative example. The all-solid-state battery 100X (single cell 9X) of the second comparative example has an insulating member 4 (insulating layer 41, expansion absorption layer 42) in the same manner as the all-solid-state battery 100 (single cell 9) of the first embodiment. However, although the insulating layer 41 is joined to the solid electrolyte layer 12, it is not joined to the positive electrode layer 11, and a gap 411 is formed between the insulating layer 41 and the positive electrode layer 11. Similarly, although the expansion absorption layer 42 is joined to the solid electrolyte layer 12, it is not joined to the negative electrode layer 13, and a gap 421 is formed between the expansion absorption layer 42 and the negative electrode layer 13.

[0053] When charging in the above configuration, lithium metal (lithium dendrite) is deposited on the side surface facing the gap 421 of the negative electrode layer 13, and as this grows, it contacts the solid electrolyte layer 12 and penetrates the solid electrolyte layer 12, and finally reaches the positive electrode layer 11, causing a short circuit between the negative electrode layer 13 and the positive electrode layer 11.

[0054] Also, when discharging in the above configuration, lithium metal (lithium dendrite) is deposited on the side surface facing the gap 411 of the positive electrode layer 11, and at least the discharge capacity decreases.

[0055] However, in the all-solid-state battery 100 (single cell 9) of the first embodiment, since the insulating member 4 is in close contact with the power generation element portion 1, deposition of lithium metal (lithium dendrite) on the side surface of the negative electrode layer 13 during charging can be suppressed, and a short circuit between the negative electrode layer 13 and the positive electrode layer 11 can be reduced. Also, by reducing the deposition of lithium metal (lithium dendrite) on the side surface of the positive electrode layer 11 during discharging, a decrease in the discharge capacity can be suppressed.

[0056] [Effects of the First Embodiment] According to the all-solid-state battery 100 (single cell 9) of the first embodiment, a power generation element portion 1 in which a positive electrode layer 11, a solid electrolyte layer 12, and a negative electrode layer 13 are laminated is arranged, and in the all-solid-state battery 100 in which an insulating member 4 is arranged so as to cover the outer periphery of the power generation element portion 1, the insulating member 4 has a laminated structure of an insulating layer 41 having an elastic modulus of 5 GPa or less and an expansion absorption layer 42 having a lower elastic modulus than the insulating layer 41, and is in the same lamination direction as the power generation element portion 1.

[0057] With the above configuration, the insulating layer 41 can expand and contract following the expansion and contraction of the positive electrode layer 11, and the expansion absorption layer 42 can also expand and contract following the expansion and contraction of the negative electrode layer 13. Therefore, the shape retention of the entire all-solid-state battery 100 (single cell 9) during charge and discharge is improved (the amount of deformation is reduced), and the stress applied from the insulating member 4 to the positive electrode layer 11 and the negative electrode layer 13 can be reduced.

[0058] As described above, since the volume change rate of the negative electrode layer 13 is larger than that of the positive electrode layer 11, the stress applied from the negative electrode layer 13 to the expansion absorption layer 42 and the stress (restoring force) applied from the expansion absorption layer 42 to the negative electrode layer 13 become large. However, by setting the elastic modulus of the expansion absorption layer 42 to be smaller than that of the insulating layer 41, the stress (restoring force) applied from the expansion absorption layer 42 to the negative electrode layer 13 can be reduced, and accordingly, the durability of the negative electrode layer 13 can be enhanced.

[0059] Therefore, it becomes possible to non-uniformly change the volume change rate of the insulating member 4 so as to follow the volume change rate of the positive electrode layer 11 and the volume change rate of the negative electrode layer 13 during charge and discharge, respectively. Thereby, damage to the power generation element portion 1 can be reduced and the durability performance can be enhanced. Further, thereby, peeling of the insulating member 4 from the power generation element portion 1 can be reduced, so that lithium metal (lithium dendrite) is deposited on the side surface of the power generation element portion 1 (positive electrode layer 11, negative electrode layer 13) exposed by the peeling of the insulating member 4, and the growth of this can be reduced to prevent short-circuiting between the positive electrode layer 11 and the negative electrode layer 13.

[0060] Furthermore, since the insulating layer 41 with an elastic modulus of 5 GPa or less can expand and contract following the expansion and contraction of the negative electrode layer 13 to some extent, the durability of the expansion absorption layer 42 can be enhanced by reducing the amount of expansion and contraction of the expansion absorption layer 42 accordingly.

[0061] In the first embodiment, the power generation element portion 1 and the insulating member 4 are disposed between a pair of current collectors (the positive electrode current collector 2 and the negative electrode current collector 3), and the insulating layer 41 and the expansion absorption layer 42 are laminated in the direction in which the pair of current collectors (the positive electrode current collector 2 and the negative electrode current collector 3) face each other and are in close contact with the power generation element portion 1.

[0062] Thereby, by bringing the power generation element portion 1 into close contact with the insulating member 4, the occurrence of unintended side reactions during charge and discharge can be reduced. Specifically, during charging, the precipitation of lithium metal (lithium dendrite) on the side surface of the negative electrode layer 13 can be suppressed, and the short circuit between the negative electrode layer 13 and the positive electrode layer 11 can be reduced. Also, during discharging, the decrease in discharge capacity can be suppressed by reducing the precipitation of lithium metal (lithium dendrite) on the side surface of the positive electrode layer 11.

[0063] In the first embodiment, the negative electrode layer 13 contains a lithium metal or a lithium compound, and the expansion absorption layer 42 is adjacent to the current collector (the negative electrode current collector 3) among the pair of current collectors (the positive electrode current collector 2 and the negative electrode current collector 3) that is adjacent to the negative electrode layer 13.

[0064] With the above configuration, when a lithium metal is applied as the negative electrode layer 13, the expansion and contraction accompanying charge and discharge become significant. However, by joining the expansion absorption layer 42 with an elastic modulus lower than 5 GPa to the negative electrode layer 13, the application of stress (restoring force) to the negative electrode layer 13 can be reduced and the durability can be enhanced. Also, when the negative electrode layer 13 includes a lithium compound portion, the discharge capacity can be increased in the same manner as when a lithium metal is included.

[0065] [Second Embodiment, Third Embodiment] FIG. 6 is a schematic diagram (cross-sectional view) for explaining a single cell 9A included in the all-solid-state battery 100A of the second embodiment. FIG. 7 is a schematic diagram (cross-sectional view) for explaining a single cell 9B included in the all-solid-state battery 100B of the third embodiment. The all-solid-state battery 100A (single cell 9A) of the second embodiment and the all-solid-state battery 100B (single cell 9B) of the third embodiment are arranged such that the insulating member 4 is disposed so as to closely adhere to and surround the side surface of the power generation element portion 1, similar to the all-solid-state battery 100 (single cell 9) of the first embodiment. The insulating member 4 includes an insulating layer 41 and an expansion absorption layer 42, and both are joined to each other.

[0066] In the all-solid-state battery 100A (single cell 9A) of the second embodiment shown in FIG. 6, the expansion absorption layer 42 is adjacent (joined) to the negative electrode current collector 3. Further, the expansion absorption layer 42 is thicker than the negative electrode layer 13 and closely adheres to the entire side surface of the negative electrode layer 13. Thereby, the precipitation of lithium metal (lithium dendrite) on the side surface of the negative electrode layer 13 during charging can be reduced.

[0067] The insulating layer 41 is adjacent (joined) to the positive electrode current collector 2. However, the insulating layer 41 is thinner than the positive electrode layer 11, and there is a region on the solid electrolyte layer 12 side of the positive electrode layer 11 that is not in close contact with the insulating layer 41. However, this region is in close contact with the expansion absorption layer 42, and the side surface of the positive electrode layer 11 is not exposed to the outside. Thereby, the precipitation of lithium metal (lithium dendrite) on the side surface of the positive electrode layer 11 during discharging can be reduced.

[0068] In the all-solid-state battery 100A (single cell 9A) of the third embodiment shown in FIG. 7, it is adjacent (joined) to the positive electrode current collector 2. Further, the insulating layer 41 is thicker than the positive electrode layer 11 and closely adheres to the entire side surface of the positive electrode layer 11. Thereby, the precipitation of lithium metal (lithium dendrite) on the side surface of the positive electrode layer 11 during discharging can be reduced.

[0069] The expansion absorption layer 42 is adjacent (joined) to the negative electrode current collector 3. However, the expansion absorption layer 42 is thinner than the negative electrode layer 13, and there is a region on the solid electrolyte layer 12 side of the negative electrode layer 13 that is not in close contact with the expansion absorption layer 42. However, this region is in close contact with the insulating layer 41, and the side surface of the negative electrode layer 13 is not exposed to the outside. Thereby, the precipitation of lithium metal on the side surface of the negative electrode layer 13 during charging can be reduced.

[0070] From the above, the all-solid-state battery 100A (single cell 9A) of the second embodiment, the all-solid-state battery 100B (single cell 9B) of the third embodiment, and the all-solid-state battery 100 (single cell 9) of the first embodiment shown in FIG. 3 have the same discharge capacity characteristics.

[0071] [Third Comparative Example] FIG. 8 is a schematic diagram (cross-sectional view) for explaining the single cell 9Y included in the all-solid-state battery 100Y of the third comparative example. FIG. 9 is a diagram showing the relationship between the number of charge and discharge cycles of the all-solid-state battery 100Y of the third comparative example and the discharge capacity per unit mass.

[0072] The all-solid-state battery 100Y (single cell 9Y) of the third comparative example has the insulating member 4 arranged so as to be in close contact with and surround the side surface of the power generation element unit 1 in the same manner as the all-solid-state battery 100 (single cell 9) of the first embodiment. The insulating layer 41 is adjacent (joined) to the positive electrode current collector 2, and the expansion absorption layer 42 is adjacent (joined) to the negative electrode current collector 3.

[0073] However, the thickness of the insulating layer 41 is thinner than that of the positive electrode layer 11. For this reason, the side surface on the solid electrolyte layer 12 side of the positive electrode layer 11 is exposed to the outside. Therefore, lithium metal may precipitate on the side surface of the positive electrode layer 11 during discharge, thereby reducing the discharge capacity.

[0074] Similarly, the thickness of the expansion absorption layer 42 is also thinner than that of the negative electrode layer 13. For this reason, the side surface on the solid electrolyte layer 12 side of the negative electrode layer 13 is exposed to the outside. Therefore, lithium metal may precipitate on the side surface of the negative electrode layer 13 during charging, and thus the all-solid-state battery 100Y (single cell 9Y) may short-circuit.

[0075] As shown in FIG. 9, the discharge capacity per unit mass of the all-solid-state battery 100Y (single cell 9Y) of the third comparative example was about 160 [mAh / g] in the first charge-discharge cycle, but became 0 [mAh / g] in the second charge-discharge cycle. This is presumably because the positive electrode layer 11 and the negative electrode layer 13 were short-circuited for the above reasons.

[0076] [Fourth Embodiment] FIG. 10 is a schematic diagram (cross-sectional view) for explaining a single cell 9C included in the all-solid-state battery 100C of the fourth embodiment. The all-solid-state battery 100C (single cell 9C) of the fourth embodiment has a configuration similar to that of the all-solid-state battery 100 (single cell 9) of the first embodiment. That is, the insulating layer 41 is adjacent (bonded) to the positive electrode current collector 2, and the thickness of the insulating layer 41 is set to be thicker than that of the positive electrode layer 11. Similarly, the expansion absorption layer 42 is adjacent (bonded) to the negative electrode current collector 3, and the thickness of the expansion absorption layer 42 is set to be thicker than that of the negative electrode layer 13.

[0077] Also in the all-solid-state battery 100C (single cell 9C) of the fourth embodiment, the insulating layer 41 is in close contact with the entire side surface of the positive electrode layer 11, and the configuration can reduce the precipitation of lithium metal on the side surface of the positive electrode layer 11. Similarly, the expansion absorption layer 42 is in close contact with the entire side surface of the negative electrode layer 13, and the configuration can reduce the precipitation of lithium metal on the side surface of the negative electrode layer 13.

[0078] However, in the all-solid-state battery 100C (single cell 9C) of the fourth embodiment, the insulating layer 41 and the expansion absorption layer 42 are separated from each other, and a gap 43 is formed therebetween. Due to the gap 43, only the solid electrolyte layer 12 is exposed to the outside.

[0079] As a result, when the all-solid-state battery 100C (single cell 9C) is pressed from the thickness direction, the pressing force is not applied to the insulating member 4, and the pressing force is applied only to the power generation element portion 1. Therefore, the charge-discharge efficiency of the power generation element portion 1 can be increased accordingly.

[0080] When the all-solid-state battery 100C (single battery 9C) is pressed from the thickness direction, the insulating layer 41 and the expansion absorption layer 42 may come into contact with each other. Also in this case, since the pressing force applied from the outside is mainly applied to the power generation element unit 1, the charge / discharge efficiency of the power generation element unit 1 can be maintained at a high level.

[0081] As described above, the all-solid-state battery 100C (single battery 9C) of the fourth embodiment has the same discharge capacity characteristics as those of the all-solid-state battery 100 (single battery 9) of the first embodiment shown in FIG. 3.

[0082] [Fourth Comparative Example] FIG. 11 is a schematic diagram (cross-sectional view) for explaining the single battery 9Z included in the all-solid-state battery 100Z of the fourth comparative example. FIG. 12 is a diagram showing the relationship between the number of charge / discharge cycles and the discharge capacity per unit mass of the all-solid-state battery 100Z of the fourth comparative example.

[0083] The all-solid-state battery 100Z (single battery 9Z) of the fourth comparative example has a configuration similar to that of the all-solid-state battery 100 (single battery 9) of the first embodiment. However, in the all-solid-state battery 100Z (single battery 9Z) of the fourth comparative example, the thickness of the insulating member 4 is thicker than that of the power generation element unit 1. Further, the insulating layer 41 protrudes toward the positive electrode current collector 2 side more than the positive electrode layer 11, and the expansion absorption layer 42 also protrudes toward the negative electrode current collector 3 side more than the negative electrode layer 13. That is, a gap 21 is formed between the positive electrode layer 11 and the positive electrode current collector 2, and a gap 31 is formed between the negative electrode layer 13 and the negative electrode current collector 3.

[0084] When the all-solid-state battery 100Z (single battery 9Z) is pressed from the thickness direction with the above configuration, the positive electrode current collector 2 is deformed so that the gap 21 side becomes convex and the positive electrode current collector 2 comes into contact with the positive electrode layer 11. Similarly, the negative electrode current collector 3 is deformed so that the gap 31 side becomes convex and the negative electrode current collector 3 comes into contact with the negative electrode layer 13.

[0085] In the above configuration, the positions where the pressing force from the outside is most applied are the inner corner portion 412 on the end face on the positive electrode current collector 2 side of the insulating layer 41 and the inner corner portion 422 on the end face on the negative electrode current collector 3 side of the expansion absorption layer 42.

[0086] Therefore, in the power generation element portion 1, the outer peripheral portion adjacent to the inner corner portions 412 and 422 receives the strongest pressing force, while the central portion hardly receives any pressing force. For this reason, the charge-discharge efficiency in the central portion decreases, and the charge-discharge efficiency of the entire all-solid-state battery 100Z (single battery 9Z) also decreases.

[0087] Further, in the insulating member 4, since the pressing force is unevenly applied to the inner corner portions 412 and 422 as described above, the insulating member 4 deforms and peels off from the power generation element portion 1, and metallic lithium (lithium dendrite) precipitates on the peeled portion (side surface of the negative electrode layer 13). There is a risk that this metallic lithium grows and reaches the positive electrode layer 11, causing a short circuit between the positive electrode layer 11 and the negative electrode layer 13.

[0088] As shown in FIG. 12, the discharge capacity per unit mass of the all-solid-state battery 100Z (single battery 9Z) of the fourth comparative example is about 40 [mAh / g] in the first charge-discharge, which is lower than that of other embodiments and the like. This is considered to be due to the decrease in charge-discharge efficiency for the above reasons. Also, in the second charge-discharge, it became 0 [mAh / g]. This is considered to be due to the short circuit between the positive electrode layer 11 and the negative electrode layer 13 for the above reasons.

[0089] As described above, the embodiments of the present invention have been explained. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. Also, the above embodiments can be combined as appropriate.

Explanation of Reference Numerals

[0090] 100 All-solid-state battery 1 Power generation element portion 11 Positive electrode layer 12 Solid electrolyte 13 Negative electrode layer 2 Positive electrode current collector 3 Negative electrode current collector 4 Insulating member 41 Insulating layer 42 Expansion absorption layer 9 Single battery

Claims

1. In an all-solid-state battery in which a power generation element portion in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated is disposed, and an insulating member is disposed so as to be in close contact with and surround the side surface of the power generation element portion, the insulating member, has a laminated structure of an insulating layer having an elastic modulus of 5 GPa or less and an expansion absorption layer having a lower elastic modulus than the insulating layer, and is in the same lamination direction as the power generation element portion, the power generation element portion and the insulating member are disposed between a pair of current collectors, the insulating layer and the expansion absorption layer are laminated in a direction in which the pair of current collectors face each other and are in close contact with the power generation element portion, the negative electrode layer contains a lithium metal or a lithium compound, the expansion absorption layer is adjacent to the current collector among the pair of current collectors that is adjacent to the negative electrode layer, and is adjacent to both the negative electrode layer and the solid electrolyte layer and is thicker than the total thickness of the negative electrode layer and the solid electrolyte layer, the insulating layer is adjacent to the positive electrode layer and is thinner than the positive electrode layer, the insulating layer and the expansion absorption layer are joined to each other, the side surfaces of the negative electrode layer and the solid electrolyte layer are each sealed by the expansion absorption layer and are not exposed to the outside, an all-solid-state battery in which the side surface of the positive electrode layer is not exposed to the outside by being sealed by the expansion absorption layer and the insulating layer.

2. In an all-solid-state battery in which a power generation element portion in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated is disposed, and an insulating member is disposed so as to be in close contact with and surround the side surface of the power generation element portion, the insulating member, has a laminated structure of an insulating layer having an elastic modulus of 5 GPa or less and an expansion absorption layer having a lower elastic modulus than the insulating layer, and is in the same lamination direction as the power generation element portion, the power generation element portion and the insulating member are disposed between a pair of current collectors, the insulating layer and the expansion absorption layer are laminated in a direction in which the pair of current collectors face each other and are in close contact with the power generation element portion, the negative electrode layer contains a lithium metal or a lithium compound, the expansion absorption layer is adjacent to the current collector among the pair of current collectors that is adjacent to the negative electrode layer, and is adjacent to the negative electrode layer and is thinner than the negative electrode layer, the insulating layer is adjacent to both the positive electrode layer and the solid electrolyte layer and is thicker than the total thickness of the positive electrode layer and the solid electrolyte layer, the insulating layer and the expansion absorption layer are joined to each other, the side surface of the negative electrode layer is not exposed to the outside by being sealed by the expansion absorption layer and the insulating layer, An all-solid-state battery in which the side surfaces of the solid electrolyte layer and the side surfaces of the positive electrode layer are each sealed by the insulating layer and are not exposed to the outside.

3. In an all-solid-state battery in which a power generation element portion in which a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated is disposed, and an insulating member is disposed so as to be in close contact with and surround the side surface of the power generation element portion, the insulating member is a laminated structure including an insulating layer having an elastic modulus of 5 GPa or less and an expansion absorption layer having a lower elastic modulus than the insulating layer, and is in the same lamination direction as the power generation element portion, the power generation element portion and the insulating member are disposed between a pair of current collectors, the insulating layer and the expansion absorption layer are laminated in a direction in which the pair of current collectors face each other and are in close contact with the power generation element portion, the negative electrode layer contains a lithium metal or a lithium compound, the expansion absorption layer is adjacent to the current collector adjacent to the negative electrode layer among the pair of current collectors, is adjacent to the negative electrode layer, and is thicker than the thickness of the negative electrode layer, the insulating layer is adjacent to the positive electrode layer and is thicker than the thickness of the positive electrode layer, an all-solid-state battery in which the insulating layer and the expansion absorption layer are separated from each other.

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