All-solid-state batteries

Abstract

This all-solid-state battery comprises: a power generation element having a positive electrode layer, a solid electrolyte layer, and a negative electrode structure layer; and a negative electrode current collector foil connected to the negative electrode structure layer. The negative electrode current collector foil has a connection region which is a region connected to the negative electrode structure layer; and an extension region extending from the connection region toward the lateral side of the power generation element. The extension region is provided with a protective layer having a thickness that increases as the distance from the power generation element increases.

Description

Technical Field

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

Background Art

[0002] An all-solid-state battery generally includes a solid electrolyte layer, a positive electrode layer, a negative electrode layer, a positive electrode current collector foil, and a negative electrode current collector foil.

[0003] As the negative electrode current collector foil, a metal foil that can be corroded (for example, a copper foil) is often used. Therefore, improvement in corrosion resistance is required for the negative electrode current collector foil.

[0004] As a technique related to the corrosion resistance of the current collector foil, the technique described in Patent Document 1 (JP2020-198275A) can be cited. Patent Document 1 discloses a current collector for an all-solid-state battery in which coating layers are formed on both surfaces of a sheet-like conductive base material, the coating layer contains a powdery carbon material, acid-modified polyvinylidene fluoride, and poly-N-vinylpyrrolidone, the content of poly-N-vinylpyrrolidone in the coating layer is 0.099 to 5.0% by mass, the content of the powdery carbon material in the coating layer is 15.0 to 45.0% by mass, and the basis weight of the coating layer per one side of the conductive base material is 0.2 to 5.0 g / m 2 2. A current collector for an all-solid-state battery is disclosed. According to the description of Patent Document 1, this current collector for an all-solid-state battery is excellent in corrosion resistance, has low resistance, and has excellent life characteristics.

Summary of the Invention

[0005] By the way, according to the findings of the present inventors, the ease of corrosion of the negative electrode current collector foil varies depending on the position in the all-solid-state battery. Specifically, as the distance from the power generation element (a laminate composed of a solid electrolyte layer, a positive electrode layer, and a negative electrode layer) increases, the negative electrode current collector foil becomes more likely to corrode. Even in a portion where corrosion is likely to occur, it is required to sufficiently prevent the corrosion of the negative electrode current collector foil.

[0006] Therefore, an object of the present invention is to provide an all-solid-state battery that can sufficiently prevent the corrosion of the negative electrode current collector foil even at a position where corrosion is likely to progress.

[0007] According to one aspect of the present invention, an all-solid-state battery is provided. This all-solid-state battery has a power generation element having a positive electrode layer, a solid electrolyte layer, and a negative electrode structural layer stacked along the stacking direction, and a negative electrode current collector foil connected to the negative electrode structural layer. The solid electrolyte layer is sandwiched between the positive electrode layer and the negative electrode structural layer. The negative electrode structural layer is a negative electrode layer and / or a negative electrode intermediate layer. The negative electrode current collector foil has a connection region which is located on the negative electrode structural layer and connected to the negative electrode structural layer, and an extended region which extends from the connection region toward the side of the power generation element. The extended region is provided with a protective layer which becomes thicker as it moves away from the power generation element. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic plan view showing an all-solid-state battery according to an embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing section AA' of Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing the configuration of a single negative electrode current collector foil. [Figure 4] Figure 4 is a schematic diagram showing an example of the BB' section in Figure 3. [Figure 5] Figure 5 is a plan view showing the surface of the negative electrode current collector foil facing the negative electrode tab. [Figure 6] Figure 6 shows a negative electrode current collector foil in a modified example of the embodiment. [Figure 7] Figure 7 is a schematic cross-sectional view showing the configuration of the connection between the power generation element and the negative electrode current collector foil. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the attached drawings.

[0010] Figure 1 is a schematic plan view showing the all-solid-state battery 1 according to this embodiment. Figure 2 is a schematic cross-sectional view showing the AA' section of Figure 1. This all-solid-state battery 1 is a secondary battery in which charging and discharging are performed by the movement of lithium ions between the positive electrode and the negative electrode.

[0011] As shown in Figures 1 and 2, the all-solid-state battery 1 comprises a plurality of power generation elements 2, a plurality of negative electrode current collector foils 6, a plurality of positive electrode current collector foils 7, a negative electrode tab 11, a positive electrode tab 15, and an outer casing material 9. The plurality of power generation elements 2, the plurality of negative electrode current collector foils 6, and the plurality of positive electrode current collector foils 7 are housed within the outer casing material 9. The negative electrode tab 11 and the positive electrode tab 15 are positioned to penetrate the outer casing material 9, respectively (see Figure 1).

[0012] As shown in Figure 2, the multiple negative electrode current collector foils 6 and the multiple positive electrode current collector foils 7 are arranged alternately in the stacking direction. Each power generation element 2 is positioned between adjacent negative electrode current collector foils 6 and positive electrode current collector foils 7 in the stacking direction. In other words, the multiple power generation elements 2 are stacked along the stacking direction via the multiple negative electrode current collector foils 6 and the multiple positive electrode current collector foils 7.

[0013] Each power generation element 2 is the part that performs the charging and discharging function. Each power generation element 2 has a positive electrode layer 5, a solid electrolyte layer 4, and a negative electrode structural layer 3. These are stacked in the stacking direction such that the solid electrolyte layer 4 is sandwiched between the positive electrode layer 5 and the negative electrode structural layer 3. Each power generation element 2 is positioned between the positive electrode current collector 7 and the negative electrode current collector 6 such that the negative electrode structural layer 3 is connected to the negative electrode current collector 6 and the positive electrode layer 5 is connected to the positive electrode current collector 7.

[0014] The positive electrode layer 5 contains a positive electrode active material and functions as an electrode. The positive electrode layer 5 is configured to release lithium ions during charging and absorb lithium during discharge. A frame-shaped positive electrode end insulator 10 is placed around the end face of the positive electrode layer 5. The positive electrode end insulator 10 protects the end of the positive electrode layer 5.

[0015] The negative electrode structural layer 3 is provided on the solid electrolyte layer 4 and is connected to the negative electrode current collector foil 6. The negative electrode structural layer 3 is the negative electrode layer and / or the negative electrode intermediate layer.

[0016] The negative electrode layer is the layer containing the negative electrode active material, and it is the layer where the battery reaction proceeds during charging and discharging.

[0017] On the other hand, the negative electrode intermediate layer is a structure adopted, for example, in "fully deposited" all-solid-state batteries. A "fully deposited" all-solid-state battery is a battery configured such that, in a fully discharged state, lithium as the negative electrode active material is not present on the negative electrode side, and during charging, lithium ions move from the positive electrode side to the negative electrode side, depositing metallic lithium on the negative electrode current collector foil. By adopting such a configuration, an all-solid-state battery with a high volumetric energy density can be realized. However, the metallic lithium deposited on the negative electrode side during charging may damage the solid electrolyte layer. Therefore, to protect the solid electrolyte layer, a negative electrode intermediate layer may be provided on the solid electrolyte layer. In such an all-solid-state battery, the metallic lithium deposited between the negative electrode intermediate layer and the negative electrode current collector foil functions as the negative electrode. The negative electrode intermediate layer may function as a negative electrode, but it may not function as a negative electrode. In this embodiment, the negative electrode structure layer 3 is a concept that encompasses not only the negative electrode layer itself, which is the electrode, but also such a negative electrode intermediate layer.

[0018] The solid electrolyte layer 4 functions as a separator between the positive and negative electrodes and is a solid layer that is conductive to lithium ions.

[0019] Multiple negative electrode current collector foils 6 and multiple positive electrode current collector foils 7 are provided to electrically connect multiple power generation elements 2 to an external device.

[0020] A plurality of negative electrode current collector foils 6 are provided corresponding to the plurality of power generation elements 2. That is, one end of the plurality of negative electrode current collector foils 6 is connected to the negative electrode structure layers 3 included in different power generation elements 2. On the other hand, the other ends of the plurality of negative electrode current collector foils 6 are gathered together and connected to one end of the negative electrode tab 11 by welding. In FIG. 2, the welding portion between the plurality of negative electrode current collector foils 6 and the negative electrode tab 11 is described as the welding portion 12. Since they are gathered together at the other end, the distance between adjacent negative electrode current collector foils 6 is large on the side of the power generation element 2 and becomes smaller as it moves away from the power generation element 2.

[0021] Although not shown in FIG. 2, similar to the plurality of negative electrode current collector foils 6, one end of the plurality of positive electrode current collector foils 7 is connected to the positive electrode layer 5, the other ends are gathered together, and they are connected to the positive electrode tab 15 by welding.

[0022] As described above, the negative electrode tab 11 is connected to the plurality of negative electrode current collector foils 6 at one end. The other end of the negative electrode tab 11 is located outside the exterior member 9. That is, the negative electrode tab 11 extends from one end thereof so as to penetrate the exterior member 9. Although not shown in FIG. 2, similarly, the positive electrode tab 15 also extends outward from the connection portion with the plurality of positive electrode current collector foils 7 so as to penetrate the exterior member 9.

[0023] The exterior member 9 is provided to protect each component of the all-solid-state battery 1. The exterior member 9 is composed of a pair of film-like members (for example, an aluminum film, etc.). The pair of film-like members are integrated at the outer peripheral portion by welding or the like, and thereby a closed space is formed inside the exterior member 9. In the portion where the negative electrode tab 11 penetrates, the exterior member 9 is sealed to the negative electrode tab 11. The exterior member 9 is sealed to the negative electrode tab 11 through, for example, an adhesive or the like. The portion where the exterior member 9 is sealed to the negative electrode tab 11 is hereinafter referred to as the seal portion 13 (see FIG. 2). Similarly, in the portion where the positive electrode tab 15 penetrates, the exterior member 9 is also sealed to the positive electrode tab 15.

[0024] The above describes the overall configuration of the all-solid-state battery 1 according to this embodiment. In the all-solid-state battery 1 according to this embodiment, measures have been taken to prevent corrosion of the negative electrode current collector foil 6. These measures will be explained below.

[0025] The negative electrode current collector foil 6 is formed from, for example, copper, copper alloy, nickel, and nickel alloy. Such materials are prone to corrosion. Corrosion of the negative electrode current collector foil 6 should be avoided because it can lead to increased resistance and short circuits. Therefore, in this embodiment, a protective layer 8 is provided on the negative electrode current collector foil 6. By providing the protective layer 8, corrosion of each negative electrode current collector foil 6 is prevented.

[0026] This protective layer 8 will be explained in detail with reference to Figure 3. Figure 3 is a schematic cross-sectional view showing the structure of a single negative electrode current collector foil 6. For the sake of explanation, in Figure 3, the negative electrode current collector foil 6 is depicted as being in a straight position.

[0027] As shown in Figure 3, the negative electrode current collector foil 6 has a connection region 6-1 and an extension region 6-2. The connection region 6-1 is a region located on the negative electrode structural layer 3 and is connected to the negative electrode structural layer 3. On the other hand, the extension region 6-2 is a region that extends from the connection region 6-1 toward the side of the power generation element 2. The protective layer 8 is provided in the extension region 6-2. The protective layer 8 becomes thicker as it moves away from the power generation element 2 (negative electrode structural layer 3).

[0028] By adopting this configuration, corrosion of the negative electrode current collector foil 6 can be prevented even in locations where corrosion is likely to progress. In other words, according to the inventors' findings, the negative electrode current collector foil 6 is more susceptible to corrosion the further it is from the power generation element 2. This is thought to be because the further it is from the power generation element 2, the closer it is to the seal portion 13. In detail, although the outer casing material 9 is sealed to the negative electrode tab 11 at the seal portion 13, it is difficult to completely separate the inside and outside of the outer casing material 9 at the seal portion 13. Therefore, moisture may penetrate into the inside of the outer casing material 9 through the seal portion 13. As a result, humidity tends to be high in the area close to the seal portion 13 inside the outer casing material 9. High humidity makes the corrosion of the negative electrode current collector foil 6 more likely to progress. In other words, as it moves away from the power generation element 2, it gets closer to the seal portion 13, the humidity increases, and the negative electrode current collector foil 6 becomes more susceptible to corrosion. However, according to this embodiment, the protective layer 8 is provided such that it becomes thicker the further it is from the power generation element 2. Therefore, corrosion of the negative electrode current collector foil 6 can be effectively prevented in locations where corrosion is likely to occur.

[0029] Another possible cause of corrosion of the negative electrode current collector foil 6 is the presence of corrosive gases generated from the power generation element 2. For example, in an all-solid-state battery 1, the solid electrolyte layer 4 may contain a sulfide solid electrolyte. Hydrogen sulfide may be generated as a corrosive gas within the outer casing material 9, with such a sulfide solid electrolyte as the source. As shown in Figure 2, in this embodiment, the distance between adjacent negative electrode current collector foils 6 becomes narrower the further they are from the power generation element 2. The closer the distance between the negative electrode current collector foils 6 is, the higher the concentration of corrosive gases generated from the solid electrolyte layer 4 tends to be, and corrosion progresses more easily. In other words, corrosion caused by corrosive gases generated from the power generation element 2 also progresses more easily the further you are from the power generation element 2. However, according to this embodiment, since the protective layer 8 becomes thicker the further you are from the power generation element 2, corrosion of the negative electrode current collector foil 6 can be effectively prevented even in positions where corrosion by corrosive gases is likely to progress.

[0030] Preferably, the protective layer 8 is provided on both sides of each negative electrode current collector foil 6. However, the protective layer 8 may be provided on only one side. Even if the protective layer 8 is provided on only one side, it can suppress the progression of corrosion of the negative electrode current collector foil 6 compared to when the protective layer 8 is not provided at all, and thus provides a certain degree of effectiveness.

[0031] Preferably, the protective layer 8 is also provided on the end face of the negative electrode current collector foil 6. Figure 4 is a schematic diagram showing an example of the BB' cross section of Figure 3. In the example shown in Figure 3, the protective layer 8 is provided on both sides and the end face (in a direction perpendicular to the lamination direction, and the end face in a direction perpendicular to the extension direction of the negative electrode current collector foil 6) of the extended region 6-2. By providing the protective layer 8 on the end face, corrosion of the end face can be prevented. The protective layer 8 may also be provided on the end face of the negative electrode current collector foil 6 in the extension direction.

[0032] Furthermore, as shown in Figure 3, preferably, the protective layer 8 is also provided on at least a portion of the negative electrode tab 11. The negative electrode tab 11 is made of a metal (or alloy) such as copper, nickel, and stainless steel. These materials constituting the negative electrode tab 11 are also susceptible to corrosion. By providing the protective layer 8 on the negative electrode tab 11 as well, corrosion of the negative electrode tab 11 can be prevented. Note that the area inside the outer casing material 9 is more prone to corrosion. Therefore, when providing the protective layer 8 on the negative electrode tab 11, it is preferable to provide the protective layer 8 in the area inside the outer casing material 9.

[0033] The protective layer 8 provided in the inner region of the outer casing 9 on the negative electrode tab 11 is preferably thicker than the protective layer 8 provided near the power generation element 2 in the extended region 6-2. The inner region of the outer casing 9 on the negative electrode tab 11 is close to the seal portion 13. Therefore, corrosion is more likely to progress in this region than near the power generation element 2 in the extended region 6-2. By increasing the thickness of the protective layer 8 provided on the negative electrode tab 11, corrosion can be effectively prevented in the negative electrode tab 11, which is a part where corrosion is likely to progress.

[0034] Next, the configuration of the connection between the negative electrode current collector foil 6 and the negative electrode tab 11 will be described. As previously mentioned, multiple negative electrode current collector foils 6 are joined together at their ends and connected to the negative electrode tab 11 by a welded joint 12 (see Figure 2, etc.). In detail, the uppermost negative electrode current collector foil 6 of the multiple negative electrode current collector foils 6 faces (overlaps with) the negative electrode tab 11 at the tip of its extended region 6-2. Figure 5 is a plan view showing the surface of the negative electrode current collector foil 6 facing the negative electrode tab 11. As shown in Figure 5, an opening 14 is provided in the protective layer 8 on the facing surface. The welded joint 12 is provided in this opening 14. That is, the negative electrode current collector foil 6 is connected to the negative electrode tab 11 by welding at the opening 14. By adopting such a configuration, the welding strength between the negative electrode current collector foil 6 and the negative electrode tab 11 is not hindered by the protective layer 8. Therefore, the connection strength can be maintained.

[0035] Preferably, among the multiple negative electrode current collector foils 6, an opening is provided in the protective layer 8 in the region overlapping with the negative electrode tab 11, for all negative electrode current collector foils 6 except for the uppermost one. Then, a welded portion 12 is formed so as to penetrate the multiple negative electrode current collector foils 6 through the opening. This allows the multiple negative electrode current collector foils 6 to be electrically connected to the negative electrode tab 11 via the welded portion 12.

[0036] Preferably, in the negative electrode tab 11, an opening is provided in the protective layer 8 on the surface facing the negative electrode current collector foil 6. The negative electrode tab 11 is then welded to the negative electrode current collector foil 6 through this opening.

[0037] Next, the form of change in the thickness of the protective layer 8 will be described. In the example shown in Figure 3, the thickness of the protective layer 8 increases in a tapered (continuous) manner as it moves away from the power generation element 2. However, the thickness of the protective layer 8 does not necessarily have to change in a tapered manner. Figure 6 shows a negative electrode current collector foil 6 in a modified example of this embodiment. In this modified example, the thickness of the protective layer 8 changes in a step-like manner. Thus, the thickness of the protective layer 8 may change in a tapered manner or in a step-like manner.

[0038] Next, we will explain the configuration of the connection portion between each power generation element 2 and the negative electrode current collector foil 6.

[0039] In the example shown in Figure 2, in each power generation element 2, the outer edge of the solid electrolyte layer 4, when viewed along the stacking direction, is located slightly further out than the outer edges of the positive electrode layer 5 and the negative electrode structure layer 3. This is to prevent short circuits between the two electrodes due to the growth of lithium dendrites that wrap around the edges. Furthermore, the outer edge of the positive electrode end insulator 10 is located even further out than the outer edge of the solid electrolyte layer 4. Here, the thickness of the protective layer 8 near the power generation element 2 is smaller than the thickness of the negative electrode structure layer 3. The protective layer 8 is positioned in contact with the negative electrode structure layer 3. With this configuration, the protective layer 8 does not interfere with the solid electrolyte layer 4. In order to achieve sufficient charge and discharge functions in the all-solid-state battery 1, it is necessary to pressurize the all-solid-state battery 1 along the stacking direction. If the thickness of the protective layer 8 is thicker than the negative electrode structure layer 3, the protective layer 8 may interfere with the solid electrolyte layer 4, and sufficient pressure may not be applied to each power generation element 2. However, according to the configuration shown in Figure 2, since the protective layer 8 is thinner than the negative electrode structure layer 3, the protective layer 8 does not interfere with the solid electrolyte layer 4 of the power generation element 2. Therefore, the charge and discharge functions can be maintained.

[0040] Furthermore, the protective layer 8 does not necessarily need to be in contact with the negative electrode structure layer 3. Figure 7 shows a further modified example of this embodiment. In the example shown in Figure 7, a gap is formed between the protective layer 8 and the negative electrode structure layer 3. Specifically, a part of the extended region 6-2 faces the positive electrode end insulator 10 in the stacking direction (see the facing region in the figure). The end of the protective layer 8 on the negative electrode structure layer 3 side is located within this facing region and is located outside the outer peripheral edge of the solid electrolyte layer 4. The thickness of the protective layer 8 in this facing region (t1 in the figure) is smaller than the sum of the thicknesses of the negative electrode structure layer 3 and the solid electrolyte layer 4 (t2 in the figure). By adopting this configuration, the protective layer 8 does not interfere with the positive electrode end insulator 10. If the thickness t1 of the protective layer 8 is greater than the sum of the thicknesses t2 of the negative electrode structure layer 3 and the solid electrolyte layer 4, the protective layer 8 will interfere with the positive electrode end insulator 10. However, according to the modified example shown in Figure 7, since no interference occurs, sufficient pressure can be applied to each power generation element 2 despite the presence of the protective layer 8, and the charging and discharging functions can be maintained.

[0041] Next, we will explain the materials and other characteristics of each component of the all-solid-state battery 1.

[0042] (protective layer) The protective layer 8 may be made of a material that has the function of preventing metal corrosion. Preferably, the protective layer 8 is formed of a polymer material. By using a polymer material, it is possible to prevent chipping of the protective layer 8 even when stress is applied to the protective layer 8. Examples of polymer materials include acrylic resin, urethane resin, and silicone resin.

[0043] The protective layer 8 may contain additives such as fillers in addition to the polymer material. However, preferably, the protective layer 8 is formed substantially solely of the polymer material. This increases the density of the protective layer 8 and more effectively prevents corrosion of the negative electrode current collector foil 6.

[0044] The protective layer 8 can be formed, for example, by applying a liquid material containing a polymer material and drying it. In this case, the thickness of the protective layer 8 can be continuously varied by changing the amount of liquid material applied depending on the location.

[0045] Alternatively, a protective layer 8 can be formed by attaching a sheet containing polymer material or the like to the negative electrode current collector foil 6. In this case, by using multiple sheets of different thicknesses, the thickness of the protective layer 8 can be changed in stages.

[0046] The thickness of the protective layer 8 is, for example, 3 to 100 μm, preferably 5 to 50 μm, at its thickest point. Furthermore, the difference between the thickness of the thickest and thinnest parts of the protective layer 8 on the negative electrode current collector foil 6 is, for example, 3 μm or more, preferably 5 μm or more.

[0047] The presence of the protective layer 8 can be confirmed by imaging and observing the cross-section of the negative electrode current collector foil 6 using a microscope such as an SEM (Scanning Electron Microscope). The thickness of the protective layer 8 can also be measured using a microscope such as an SEM.

[0048] (Positive electrode layer) The positive electrode layer 5 can be formed from a material that releases lithium ions during charging and absorbs lithium ions during discharge. The positive electrode layer 5 can be formed from a material that includes, for example, a resin binder and a positive electrode active material dispersed in the resin binder. As the positive electrode active material, for example, a lithium metal composite oxide can be used. Examples of lithium metal composite oxides include layered rock salt type compounds such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2, LiMn2O4, and LiNi 0.5 Mn 1.5 Examples include spinel-type compounds such as O4, olivine-type compounds such as LiFePO4 and LiMnPO4, or Si-containing compounds such as Li2FeSiO4 and Li2MnSiO4. Also, Li4Ti5O 12 Other options can also be used.

[0049] The thickness of the positive electrode layer 5 is not particularly limited, but is, for example, 10 to 500 μm, preferably 50 to 200 μm.

[0050] (Negative electrode structure layer) As previously described, the negative electrode structure layer 3 may be either a negative electrode layer or a negative electrode intermediate layer. The negative electrode structure layer 3 may be both a negative electrode layer and a negative electrode intermediate layer. The thickness of the negative electrode structure layer 3 is, for example, 1 to 100 μm, preferably 5 to 80 μm.

[0051] The negative electrode layer can be any layer configured to absorb (or deposit) lithium during charging and release lithium ions during discharge. For example, the negative electrode layer can be formed from a material comprising a resin binder and a negative electrode active material dispersed in the resin binder. Examples of negative electrode active materials that can be used include lithium metal, silicon materials, tin materials, compounds containing silicon or tin (oxides, nitrides, alloys with other metals), and carbon materials (graphite, etc.).

[0052] The negative electrode intermediate layer only needs to have the function of protecting the solid electrolyte layer 4 from lithium metal generated on the negative electrode side during charging. The negative electrode intermediate layer contains, for example, a lithium-reactive material. Examples of lithium-reactive materials include materials that can intercept and deintercept lithium ions during charging, and metals that can alloy with lithium during charging.

[0053] While there are no particular limitations on the material capable of intercalating and deintercalating lithium ions, carbon materials are preferred. Specific examples of carbon materials include carbon black (specifically, acetylene black, Ketjenblack®, furnace black, channel black, thermal lamp black, etc.), carbon nanotubes (CNTs), graphite, and hard carbon. Among these, carbon black is preferred, and it is more preferable that it be at least one selected from the group consisting of acetylene black, Ketjenblack®, furnace black, channel black, and thermal lamp black.

[0054] Examples of metals that can be alloyed with lithium include In, Al, Si, Sn, Mg, Au, Ag, and Zn. Among these, In, Si, Sn, and Ag are preferred, with Ag being more preferred.

[0055] The lithium-reactive material may be used alone or in combination of two or more types. In the case of using two or more types in combination, it is preferable to use a material capable of intercalating and deintercalating lithium ions in combination with a metal that can alloy with lithium. This ensures sufficient strength and lithium-ion conductivity in the negative electrode intermediate layer. More specifically, it is preferable to use nanoparticles made of In, Si, Sn, and Ag in combination with carbon black, and more preferably to use nanoparticles made of Ag in combination with carbon black. When using a material capable of intercalating and deintercalating lithium ions in combination with a metal that can alloy with lithium, the mixing ratio (mass ratio) is not particularly limited, but the ratio of the material capable of intercalating and deintercalating lithium ions to the metal that can alloy with lithium is preferably 10:1 to 1:1, and more preferably 5:1 to 2:1.

[0056] The content of lithium-reactive material in the negative electrode intermediate layer (referring to the total content of two or more materials if they are used in combination; the same applies hereinafter) is not particularly limited, but is preferably in the range of 50 to 100% by mass, more preferably in the range of 70 to 100% by mass, even more preferably in the range of 85 to 99% by mass, and particularly preferably in the range of 90 to 100% by mass.

[0057] The negative electrode intermediate layer may consist solely of lithium-reactive material if a self-supporting film can be fabricated using only lithium-reactive material, but may also contain a binder as needed. The type of binder is not particularly limited, and any known binder in the art can be used as appropriate. Examples include polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethylcellulose.

[0058] The binder content in the negative electrode intermediate layer is not particularly limited, but is preferably in the range of 1 to 15% by mass, and more preferably in the range of 5 to 10% by mass. If the binder content is 1% by mass or more, a negative electrode intermediate layer with sufficient strength can be formed. If the binder content is 15% by mass or less, a negative electrode intermediate layer with sufficient lithium ion conductivity can be formed.

[0059] The thickness of the negative electrode intermediate layer is not particularly limited, but is preferably 1 to 50 μm, more preferably 5 to 40 μm, and even more preferably 10 to 30 μm. When the thickness of the negative electrode intermediate layer is 1 μm or more, the functions of the negative electrode intermediate layer can be fully exhibited. When the thickness of the negative electrode intermediate layer is 50 μm or less, the decrease in energy density can be suppressed.

[0060] In a preferred embodiment, the negative electrode structural layer 3 includes carbon particles (such as carbon black), metal particles (such as silver particles), and a binder (resin binder). By using such a configuration, it becomes possible to effectively protect the solid electrolyte layer 4 from lithium dendrites that form on the negative electrode side. Thus, short circuits between the two electrodes caused by lithium dendrites are prevented.

[0061] (solid electrolyte layer) The solid electrolyte layer 4 is a solid and can function as an electrolyte layer in a secondary battery; its material is not particularly limited. For example, the solid electrolyte layer 4 can be formed from a sulfide or oxide. Preferably, the solid electrolyte layer 4 contains a sulfide solid electrolyte. When a sulfide solid electrolyte is used, as previously described, the negative electrode current collector foil 6 is susceptible to corrosion by hydrogen sulfide. However, according to this embodiment, since a protective layer 8 is provided in a specific configuration, corrosion of the negative electrode current collector foil 6 can be prevented even when a sulfide solid electrolyte is used. Examples of sulfide solid electrolytes include LPS-based (e.g., argyrodite (Li6PS5Cl)) and LGPS-based (e.g., Li 10 GeP2S 12 Examples of materials include the following. The thickness of the solid electrolyte layer 4 is not particularly limited, but is, for example, 5 to 100 μm, preferably 20 to 60 μm.

[0062] (Negative electrode current collector foil) As the negative electrode current collector foil 6, a metal foil that is susceptible to corrosion is used. Examples of metal foils include copper, copper alloys, nickel, and nickel alloys. According to this embodiment, since the structure of the protective layer 8 is designed, corrosion can be prevented even if a metal foil susceptible to corrosion is used as the negative electrode current collector foil 6.

[0063] (Positive current collector foil) For the positive electrode current collector foil 7, a metal foil that is resistant to corrosion is used. For example, aluminum foil can be used as the positive electrode current collector foil.

[0064] (Negative electrode tab) The negative electrode tab 11 can be any conductive material. For example, materials that can make up the negative electrode tab 11 include metals such as copper, nickel, and stainless steel, as well as alloys of these with other metals. Even if a material that may corrode is used for the negative electrode tab 11, according to this embodiment, corrosion of the negative electrode tab 11 can be prevented by providing a protective layer 8 of a specific thickness.

[0065] (Positive tab) The positive electrode tab 15 can be any conductive material. For example, an aluminum tab can be used as the positive electrode tab 15.

[0066] (Manufacturing method) The method for manufacturing the all-solid-state battery 1 according to this embodiment is not particularly limited. An example of the manufacturing method for the all-solid-state battery 1 will be described below.

[0067] [Fabrication of the positive electrode layer] A slurry is prepared by weighing and mixing predetermined amounts of positive electrode active material, sulfide solid electrolyte, conductive additive, binder, and xylene. The prepared slurry is applied to both sides of a carbon-coated Al foil (positive electrode current collector foil 7) and dried. This provides a positive electrode current collector foil 7 with a positive electrode layer 5 having a thickness of 200 μm (100 μm on each side).

[0068] [Fabrication of positive electrode end insulator] A predetermined amount of alumina, binder, and xylene are weighed and mixed to prepare a slurry. The prepared slurry is applied around the positive electrode layer 5 using a dispenser. This creates the positive electrode end insulator 10.

[0069] [Preparation of a solid electrolyte layer] A predetermined amount of sulfide solid electrolyte, binder, and xylene is weighed and mixed to prepare a slurry. The prepared slurry is coated onto a SUS foil and dried to create a solid electrolyte layer 4 with a thickness of 40 μm.

[0070] [Fabrication of the negative electrode structure layer] A predetermined amount of negative electrode active material (or, in the case of preparing a negative electrode intermediate layer, silver particles and carbon particles), binder, and NMP (N-methylpyrrolidone) is weighed and mixed to prepare a slurry. The prepared slurry is applied to a SUS foil and dried to prepare a negative electrode structure layer 3 with a thickness of 20 μm (10 μm on each side).

[0071] [Fabrication of positive electrode / solid electrolyte / negative electrode laminates] A solid electrolyte layer 4 is placed on the positive electrode layer 5 and roll-pressed. This transfers the solid electrolyte layer 4 from the SUS foil onto the positive electrode layer 5. Furthermore, a negative electrode structure layer 3 is placed on the solid electrolyte layer 4 and roll-pressed. This transfers the negative electrode structure layer 3 from the SUS foil onto the solid electrolyte layer 4. This results in a positive electrode / solid electrolyte / negative electrode laminate.

[0072] [Laminated cell fabrication] Multiple layers of a positive electrode / solid electrolyte / negative electrode laminate and a negative electrode current collector foil 6, each with a protective layer 8 provided at a predetermined position, are laminated and integrated. Then, Al tabs are joined to the positive electrode current collector foil 7 and Ni-plated copper tabs (with the protective layer 8 formed as needed) are joined to the negative electrode current collector foil 6 using an ultrasonic welding machine. Finally, the laminate is placed in an aluminum laminate film (outer packaging material 9) and vacuum sealed. This yields the all-solid-state battery 1 according to this embodiment.

[0073] Embodiments of the present invention have been described above. In these embodiments, the case in which the all-solid-state battery 1 includes multiple power generation elements 2 has been described. However, the all-solid-state battery 1 does not necessarily need to include multiple power generation elements 2, and the power generation element 2 may be a single element. In this case, the negative electrode current collector foil 6 and the positive electrode current collector foil 7 may also be a single element.

[0074] Next, we will summarize some representative aspects of the relationship between the configuration and effects of this embodiment.

[0075] The all-solid-state battery 1 according to this embodiment includes a power generation element 2 having a positive electrode layer 5, a solid electrolyte layer 4, and a negative electrode structure layer 3 stacked along the stacking direction, and a negative electrode current collector foil 6 connected to the negative electrode structure layer 3. The solid electrolyte layer 4 is sandwiched between the positive electrode layer 5 and the negative electrode structure layer 3. The negative electrode structure layer 3 is the negative electrode layer and / or the negative electrode intermediate layer. The negative electrode current collector foil 6 includes a connection region 6-1, which is located on the negative electrode structure layer 3 and is connected to the negative electrode structure layer 3, and an extended region 6-2, which extends from the connection region 6-1 toward the side of the power generation element 2. The extended region 6-2 is provided with a protective layer 8 such that it becomes thicker as it moves away from the power generation element 2. With this configuration, the protective layer 8 is thicker in areas further away from the power generation element 2, which are areas where the negative electrode current collector foil 6 is prone to corrosion. Therefore, corrosion of the negative electrode current collector foil 6 can be effectively prevented even in areas prone to corrosion.

[0076] Preferably, the all-solid-state battery 1 has an outer casing 9 that houses the power generation element 2 and the negative electrode current collector foil 6, and a negative electrode tab 11 connected to the negative electrode current collector foil 6 at one end. The negative electrode tab 11 extends from one end of the negative electrode tab 11 so as to penetrate the outer casing 9. The outer casing 9 is sealed to the negative electrode tab 11 at the portion through which the negative electrode tab 11 penetrates. The protective layer 8 is thicker in the portion closer to the seal portion 13 between the outer casing 9 and the negative electrode tab 11. In an all-solid-state battery 1 with such a configuration, the further away from the power generation element 2, the closer to the seal portion 13. In the region close to the seal portion 13, humidity tends to be high due to moisture entering through the seal portion 13. As a result, corrosion of the negative electrode current collector foil 6 is likely to occur. However, according to this embodiment, since the protective layer 8 is thicker in the region further away from the power generation element 2, corrosion of the negative electrode current collector foil 6 can be effectively prevented even in locations that are prone to corrosion from a humidity standpoint.

[0077] More preferably, the end of the extended region 6-2 is provided with an opposing surface facing the negative electrode tab 11. An opening 14 is provided in the protective layer 8 on this opposing surface. The negative electrode current collector foil 6 is joined to the negative electrode tab 11 by welding through the opening 14. With this configuration, the welding strength between the negative electrode current collector foil 6 and the negative electrode tab 11 can be maintained despite the presence of the protective layer 8.

[0078] More preferably, the protective layer 8 is also provided in the area inside the outer covering material 9 on the negative electrode tab 11. The protective layer 8 provided on the negative electrode tab 11 is thicker than the protective layer provided near the power generation element 2 in the extended region 6-2. The area inside the outer covering material 9 on the negative electrode tab 11 is close to the seal portion 13, and corrosion of the negative electrode tab 11 is likely to occur there. Therefore, by increasing the thickness of the protective layer 8 in such a location, corrosion can be effectively prevented even in areas of the negative electrode tab 11 where corrosion is likely to progress.

[0079] Preferably, there are multiple power generation elements 2. The multiple power generation elements 2 are stacked along the stacking direction. Multiple negative electrode current collector foils 6 are provided corresponding to the multiple power generation elements 2. The multiple negative electrode current collector foils 6 are connected to the negative electrode structural layer 3 of different power generation elements 2. The multiple negative electrode current collector foils 6 are joined together at the end of the extended region 6-2 to form a single foil. In an all-solid-state battery having such a configuration, the spacing between the multiple negative electrode current collector foils 6 becomes narrower as you move away from the power generation elements 2. In areas where the spacing between the negative electrode current collector foils 6 is narrow, corrosion due to corrosive gases generated from the power generation elements 2 is more likely to progress. In other words, corrosion is more likely to occur as you move away from the power generation elements 2, from the perspective of corrosive gases. However, according to this embodiment, the protective layer 8 is thicker in areas further away from the power generation elements 2, so corrosion of the negative electrode current collector foils 6 can be effectively prevented even in locations where corrosion is more likely to progress from the perspective of corrosive gases.

[0080] Preferably, the protective layer 8 is continuously or steppedly thickened in the direction away from the power generation element 2. This configuration effectively prevents corrosion of the negative electrode current collector foil 6.

[0081] Preferably, the all-solid-state battery 1 has a positive electrode end insulator 10 positioned to cover the end of the positive electrode layer 5. A portion of the extending region 6-2 faces the positive electrode end insulator 10 in the stacking direction. The thickness of the protective layer 8 in the region facing the positive electrode end insulator 10 is smaller than the sum of the thickness of the negative electrode structure layer 3 and the solid electrolyte layer 4. With this configuration, the protective layer 8 does not interfere with the positive electrode end insulator 10, so sufficient pressure can be applied to the power generation element 2 and the charge / discharge function is not hindered.

[0082] Preferably, the protective layer 8 is also provided on the end face of the negative electrode current collector foil 6. With this configuration, corrosion can be prevented even on the end face of the negative electrode current collector foil 6.

[0083] Preferably, the protective layer 8 contains a polymer material. With this configuration, the protective layer 8 is less likely to be damaged even when force is applied to it. Therefore, corrosion of the negative electrode current collector foil 6 can be prevented more reliably.

[0084] More preferably, the protective layer 8 consists solely of a polymer material. With such a configuration, the protective layer 8 becomes denser. As a result, corrosion of the negative electrode current collector foil 6 can be prevented more reliably.

[0085] Preferably, the negative electrode structural layer 3 includes carbon particles, metal particles, and a binder. With this configuration, even if lithium dendrites form on the negative electrode side during charging, the solid electrolyte layer 4 is protected by the negative electrode structural layer 3. Thus, short circuits between the two electrodes due to lithium dendrites are prevented.

[0086] Preferably, the power generation element 2 is configured such that metallic lithium is deposited on the negative electrode side of the solid electrolyte layer 4 during charging. By adopting such a configuration, an all-solid-state battery with a high volumetric energy density can be realized.

[0087] Although embodiments of the present invention have been described above, these embodiments only represent 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.

Claims

1. A power generation element having a positive electrode layer, a solid electrolyte layer, and a negative electrode structural layer stacked along the stacking direction, A negative electrode current collector foil connected to the aforementioned negative electrode structural layer, It has, The solid electrolyte layer is sandwiched between the positive electrode layer and the negative electrode structural layer. The negative electrode structural layer is a negative electrode layer and / or a negative electrode intermediate layer. The aforementioned negative electrode current collector foil is A connection region is a region located on the negative electrode structural layer and connected to the negative electrode structural layer, The system comprises an extending region that extends from the connection region toward the side of the power generation element, A protective layer is provided in the extended region such that it becomes thicker as it moves away from the power generation element. All-solid-state battery.

2. A solid-state battery as described in claim 1, Furthermore, An exterior material housing the power generation element and the negative electrode current collector foil, A negative electrode tab, connected at one end to the negative electrode current collector foil, It has, The negative electrode tab extends from one end of the negative electrode tab so as to penetrate the outer casing material. The exterior material is sealed to the negative electrode tab in the portion through which the negative electrode tab penetrates. The protective layer is thicker in the portion closer to the seal between the exterior material and the negative electrode tab. All-solid-state battery.

3. A solid-state battery as described in claim 2, The end of the extended region is provided with an opposing surface that faces the negative electrode tab. On the opposing surface, the protective layer is provided with an opening. The negative electrode current collector foil is joined to the negative electrode tab by welding through the opening. All-solid-state battery.

4. A solid-state battery according to claim 2 or 3, The protective layer is also provided in the area inside the outer covering material of the negative electrode tab. The protective layer provided on the negative electrode tab is thicker than the protective layer provided near the power generation element in the extended region. All-solid-state battery.

5. A solid-state battery according to claim 1 or 2, Multiple such power generation elements are provided. The aforementioned multiple power generation elements are stacked along the stacking direction, The negative electrode current collector foil is provided in multiple quantities, corresponding to the multiple power generation elements. The plurality of negative electrode current collector foils are connected to the negative electrode structural layers of different power generation elements. The plurality of negative electrode current collector foils are joined together at the end of the extended region to form a single unit. All-solid-state battery.

6. A solid-state battery according to claim 1 or 2, The protective layer is thickened continuously or in a stepped manner in the direction away from the power generation element. All-solid-state battery.

7. A solid-state battery according to claim 1 or 2, Furthermore, The positive electrode layer has a positive electrode end insulator that is positioned to cover the end of the positive electrode layer, A portion of the aforementioned extending region faces the positive electrode end insulator in the stacking direction. The thickness of the protective layer in the region facing the positive electrode end insulator is smaller than the sum of the thickness of the negative electrode structural layer and the thickness of the solid electrolyte layer. All-solid-state battery.

8. A solid-state battery according to claim 1 or 2, The protective layer is also provided on the end face of the negative electrode current collector foil. All-solid-state battery.

9. A solid-state battery according to claim 1 or 2, The protective layer contains a polymer material. All-solid-state battery.

10. A solid-state battery as described in claim 9, The protective layer consists solely of the polymer material. All-solid-state battery.

11. A solid-state battery according to claim 1 or 2, The negative electrode structural layer comprises carbon particles, metal particles, and a binder. All-solid-state battery.

12. A solid-state battery as described in claim 11, The power generation element is configured such that metallic lithium is deposited on the negative electrode side of the solid electrolyte layer during charging. All-solid-state battery.

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