Electricity storage device member and electricity storage device

Abstract

To provide a power storage device member and a power storage device capable of improving charge / discharge characteristics by using an alkali metal ion as a carrier ion.SOLUTION: A power storage device member includes a solid electrolyte layer 2 including an alkali metal ion conductive solid electrolyte, an alkali metal layer 3 laminated on the solid electrolyte layer 2 and including an alkali metal, and an electrode layer that is laminated on the alkali metal layer 3 and includes a material that can occlude and release an alkali metal ion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a member for an electricity storage device and an electricity storage device using the member for an electricity storage device. [Background technology]

[0002] Lithium-ion secondary batteries have established themselves as high-capacity, lightweight power sources essential for mobile devices, electric vehicles, and other applications. However, current lithium-ion secondary batteries primarily use flammable organic electrolytes, raising concerns about the risk of fire. To address this issue, development of all-solid-state batteries using solid electrolytes instead of organic electrolytes is underway. Furthermore, due to concerns about the rising cost of lithium raw materials worldwide, research into all-solid-state sodium-ion batteries as an alternative has been underway in recent years.

[0003] Patent Document 1 discloses an example of an all-solid-state sodium ion battery in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked in this order. 1+y Zr2(SiO4) y (PO4) 3-y It consists of an oxide solid electrolyte represented by (1≦y<3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-015782 Summary of the Invention [Problem to be solved by the invention]

[0005] In all-solid-state batteries, it is difficult to form an ion conduction path between the solid electrolyte layer and the electrode layer, which may result in poor charge-discharge characteristics.

[0006] An object of the present invention is to provide a member for an electricity storage device and an electricity storage device that can improve charge / discharge characteristics by using alkali metal ions as carrier ions. [Means for solving the problem]

[0007] The electricity storage device member of the present invention is characterized by comprising: a solid electrolyte layer containing an alkali metal ion-conductive solid electrolyte; an alkali metal layer laminated on the solid electrolyte layer and containing an alkali metal; and an electrode layer laminated on the alkali metal layer and containing a material capable of absorbing and releasing alkali metal ions.

[0008] The electrode layer is preferably a negative electrode layer. In this case, the negative electrode active material contained in the negative electrode layer is preferably a compound containing at least one selected from the group consisting of a metal, an alloy, graphite, and hard carbon, and the same alkali metal element as the alkali metal element contained in the alkali metal layer.

[0009] At least a portion of the negative electrode layer is preferably made of an alloy containing the same type of alkali metal element as the alkali metal element contained in the alkali metal layer.

[0010] It is preferable that the alkali metal contained in the alkali metal layer is diffused into the negative electrode layer.

[0011] More preferably, the alkali metal element contained in the alkali metal layer is Na, and the negative electrode active material is a compound containing Na.

[0012] The negative electrode active material preferably contains at least one element selected from the group consisting of Sn, Bi, Sb, and Pb.

[0013] This is suitable when the electrode layer contains a binder. It is preferable that the solid electrolyte layer contains an oxide.

[0014] The thickness of the alkali metal layer is preferably 5 nm or more and 500 μm or less.

[0015] The electricity storage device according to the present invention includes the electricity storage device member described above, and further includes a second electrode layer that is stacked on the solid electrolyte layer so as to sandwich the solid electrolyte layer together with the alkali metal layer, and that serves as a first electrode layer of the electrode layer of the electricity storage device member. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide an electricity storage device member and an electricity storage device that use alkali metal ions as carrier ions and can improve charge / discharge characteristics. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a front cross-sectional view of an electricity storage device member according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a front cross-sectional view of an electricity storage device member according to a modified example of the first embodiment of the present invention. [Figure 3] FIG. 6 is a front cross-sectional view of an electricity storage device according to a second embodiment of the present invention. [Figure 4] 10(a) and 10(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device according to a second embodiment of the present invention. [Figure 5] 10(a) and 10(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device according to a second embodiment of the present invention. [Figure 6] 10(a) and 10(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device according to a second embodiment of the present invention. [Figure 7] 10(a) and 10(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device according to a second embodiment of the present invention. [Figure 8] 10(a) and 10(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device using an electricity storage device member according to a modified example of the first embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0019] [Electricity storage device materials] (First embodiment) Fig. 1 is a front cross-sectional view of an electricity storage device member according to a first embodiment of the present invention. As shown in Fig. 1, the electricity storage device member 1 includes a solid electrolyte layer 2, an alkali metal layer 3, and an anode layer 4. Specifically, the alkali metal layer 3 is laminated on the solid electrolyte layer 2. The anode layer 4 is laminated on the alkali metal layer 3.

[0020] The solid electrolyte layer 2 contains an alkali metal ion conductive solid electrolyte. The negative electrode layer 4 is an electrode layer according to the present invention that contains a material capable of absorbing and desorbing alkali metal ions. However, the electrode layer that contains a material capable of absorbing and desorbing alkali metal ions does not necessarily have to be a negative electrode layer, and may be a positive electrode layer.

[0021] The alkali metal layer 3 can be made of an appropriate alkali metal such as Li, Na, or K. The thickness of the alkali metal layer 3 is preferably 5 nm or more, more preferably 50 nm or more, and even more preferably 500 nm or more. This allows the solid electrolyte layer 2 and the anode layer 4 to be suitably bonded by the alkali metal layer 3. There is no particular upper limit to the thickness of the alkali metal layer 3, but it is preferably 500 μm or less, for example. If the alkali metal layer 3 is too thick, safety may be compromised. In this embodiment, the thickness of the anode layer 4 is thicker than the thickness of the alkali metal layer 3. In this case, safety can be suitably improved.

[0022] The negative electrode active material of the negative electrode layer 4 may be a metal foil or a composite. When the negative electrode layer 4 is a composite, it preferably contains a conductive additive and a binder. The binder can suitably bind the powder constituting the negative electrode active material. The conductive additive can form a conductive path, thereby reducing the internal resistance of the negative electrode layer 4.

[0023] At least a portion of the negative electrode layer 4 is composed of a compound containing the same type of alkali metal element as the alkali metal element contained in the alkali metal layer 3. Specifically, the alkali metal contained in the alkali metal layer 3 is diffused into the negative electrode layer 4. Therefore, at least a portion of the negative electrode layer 4 near the surface in contact with the alkali metal layer 3 is composed of the compound containing the alkali metal element. When the negative electrode active material of the negative electrode layer 4 is a metal foil-based material, the compound containing the alkali metal element is an alloy containing the alkali metal element. When the negative electrode active material of the negative electrode layer 4 is a composite-based material containing a metal, the compound containing the alkali metal element may also be an alloy containing the alkali metal element.

[0024] Here, the negative electrode layer 4 has an outer main surface 4a. The outer main surface 4a is a main surface located on the outer side of the electricity storage device member 1. In this embodiment, the composition ratio of the alkali metal element in the negative electrode layer 4 decreases toward the outer main surface 4a. In this manner, the composition ratio of the alkali metal element in the negative electrode layer 4 has a gradient. However, the composition ratio of the alkali metal in the negative electrode layer 4 may be uniform. Note that the negative electrode layer 4 does not necessarily contain the alkali metal element.

[0025] A feature of this embodiment is that, in the electricity storage device member 1, the alkali metal layer 3 is laminated between the solid electrolyte layer 2 and the anode layer 4. Because both the solid electrolyte layer 2 and the anode layer 4 are in contact with the alkali metal layer 3, an ion conduction path can be easily formed. In addition, because the alkali metal layer 3 is highly flexible, the surface shape of the alkali metal layer 3 can easily conform to the surface shapes of both the solid electrolyte layer 2 and the anode layer 4. This effectively increases the adhesion between the alkali metal layer 3 and both the solid electrolyte layer 2 and the anode layer 4. This effectively increases the ion conduction path. As a result, the charge / discharge characteristics of an electricity storage device using the electricity storage device member 1 can be improved.

[0026] A current collector layer 5 is laminated on the negative electrode layer 4. The current collector layer 5 does not necessarily have to be provided. However, the provision of the current collector layer 5 allows for efficient current collection.

[0027] (Variation) FIG. 2 is a front cross-sectional view of an electricity storage device member according to a modified example of the first embodiment. In the electricity storage device member 11, the negative electrode active material of the negative electrode layer 14 is a metal foil. The negative electrode layer 14 contains an alloy of a metal capable of absorbing and releasing alkali metal ions and a metal that does not absorbing and releasing alkali metal ions. This reduces the volume change of the negative electrode layer 14 that accompanies the absorption and release of alkali ions during charge and discharge, thereby improving the cycle characteristics. Note that no current collector layer is formed on the negative electrode layer 14.

[0028] The electrical resistance of the metal used in the negative electrode layer 14 that does not absorb and release alkali metal ions is preferably lower than the electrical resistance of the metal used in the negative electrode layer 14 that can absorb and release alkali metal ions. In this case, current can be collected efficiently even without a current collector layer.

[0029] In this modification, at least a portion of the negative electrode layer 14 is composed of a compound containing the same type of alkali metal element as the alkali metal element contained in the alkali metal layer 3. Specifically, at least a portion of the negative electrode layer 14 near the surface in contact with the alkali metal layer 3 is composed of an alloy containing the alkali metal element. The composition ratio of the alkali metal element in the negative electrode layer 14 decreases toward the outer main surface 14a.

[0030] The member for an electricity storage device according to the present invention can be used in an electricity storage device such as an all-solid-state battery, for example.

[0031] [Energy storage devices] (Second embodiment) FIG. 3 is a front cross-sectional view of an electricity storage device according to a second embodiment of the present invention. As shown in FIG. 3, an all-solid-state battery 20 serving as an electricity storage device includes a positive electrode layer 26 and the electricity storage device member 1 of the first embodiment. The positive electrode layer 26 is laminated on the solid electrolyte layer 2 of the electricity storage device member 1. Specifically, the positive electrode layer 26 is laminated on the solid electrolyte layer 2 so as to sandwich the solid electrolyte layer 2 together with the alkali metal layer 3. In this embodiment, the negative electrode layer 4 corresponds to the first electrode layer in the present invention, and the positive electrode layer 26 corresponds to the second electrode layer in the present invention. A current collector layer 27 is laminated on the positive electrode layer 26. However, the current collector layer 27 does not necessarily have to be provided.

[0032] A feature of this embodiment is that in the electricity storage device member 1, the alkali metal layer 3 is laminated between the solid electrolyte layer 2 and the anode layer 4. Because both the solid electrolyte layer 2 and the anode layer 4 are in contact with the alkali metal layer 3, an ion conduction path can be easily formed. In addition, because the alkali metal layer 3 is highly flexible, the surface shape of the alkali metal layer 3 can easily conform to the surface shapes of both the solid electrolyte layer 2 and the anode layer 4. This effectively increases the adhesion between the alkali metal layer 3 and both the solid electrolyte layer 2 and the anode layer 4. This effectively increases the ion conduction path. This improves the charge / discharge characteristics of the electricity storage device.

[0033] If the anode layer 4 contains an organic binder, P2O5, SiO2, or the like, a depletion layer where ions are not present may form in the ion conduction path, and carrier ions may be trapped in the depletion layer. As a result, the discharge capacity and cycle characteristics may be reduced. In contrast, in the energy storage device member 1, carrier ions can be supplied by the alkali metal layer 3. This can also improve the charge / discharge efficiency and cycle characteristics. As such, the present invention is particularly suitable when the anode layer 4 contains an organic binder or the like, which is a material that may cause a depletion layer.

[0034] Furthermore, since the solid electrolyte layer 2 and the negative electrode layer 4 are joined via the alkali metal layer 3, the negative electrode layer 4 is less likely to peel off. This makes it possible to effectively improve cycle characteristics. In addition, since the negative electrode layer 4 is less likely to peel off even when the amount of negative electrode active material carried is increased, the capacity can be effectively increased.

[0035] When the negative electrode active material of the negative electrode layer 4 contains an oxide such as SnO, a conversion reaction occurs during the first charge. When the alkali metal is Li and the oxide is SnO, the reaction formula for the conversion reaction is SnO + 2Li + +2e - →Sn + Li2O. Sn reduced from SnO by the conversion reaction is expressed as Sn + 4.4Li + +4.4e - →SnLi 4.4 This alloying is reversible, and upon discharge, Li + On the other hand, the conversion reaction is basically irreversible. Therefore, during discharge, Li in Li2O + is not released, and the electrons equivalent to the amount of SnO reduced in the conversion reaction are not released either. Therefore, electrons are consumed in the conversion reaction, and the initial charge-discharge efficiency is likely to deteriorate.

[0036] Here, as in this embodiment, the negative electrode layer 4 is preferably a compound containing the same type of alkali metal element as the alkali metal element contained in the alkali metal layer 3. In this case, for example, when the negative electrode active material contains Sn and the alkali metal element is Li, the negative electrode layer 4 also contains an alloy of Sn and Li. Therefore, in the first discharge, the Li in the alloy + and electrons are released. Therefore, even if a conversion reaction occurs during the first charge, the consumption of electrons can be offset. Therefore, the charge / discharge efficiency can be improved. As such, this embodiment is particularly suitable when the negative electrode active material of the negative electrode layer 4 contains an oxide.

[0037] The following describes in detail the negative electrode layer 4, solid electrolyte layer 2, positive electrode layer 26, current collector layer 5, and current collector layer 27, which are electrode layers containing a material capable of absorbing and releasing alkali metal ions and are used in the all-solid-state battery 20.

[0038] Anode layer (an electrode layer capable of absorbing and releasing alkali metal ions); When the negative electrode active material of the negative electrode layer 4 is a metal foil, the negative electrode active material contains a metal or an alloy. Specifically, the negative electrode active material preferably contains at least one element selected from the group consisting of Al, Si, Ge, Sn, Bi, Sb, and Pb. When Li is used in the alkali metal layer 3, the negative electrode active material preferably contains at least one element selected from the group consisting of Al, Si, Ge, Sn, Sb, and Pb. On the other hand, when Na is used in the alkali metal layer 3, the negative electrode active material preferably contains at least one element selected from the group consisting of Sn, Bi, Sb, and Pb.

[0039] The negative electrode layer 4 may contain a metal element that does not absorb and release alkali metal ions. Specific examples of metal elements that do not absorb and release Li include Zn, Cu, Ni, Co, Mg, and Mo. Examples of metal elements that do not absorb and release alkali metal ions include Zn, Cu, Ni, Co, Si, Al, Mg, Mo, and Fe.

[0040] When the negative electrode active material of the negative electrode layer 4 is a metal foil, examples of the method for forming the negative electrode layer 4 include physical vapor deposition methods such as vapor deposition or sputtering, and chemical vapor deposition methods such as thermal CVD, MOCVD, and plasma CVD. Other methods for forming the negative electrode layer 4 include plating, a sol-gel method, and a liquid phase film formation method using spin coating. A metal layer capable of absorbing and desorbing alkali metal ions may be laminated by the above-mentioned method on a metal layer containing a metal element that does not occlude and desorb alkali metal ions, and then alloyed.

[0041] When the negative electrode active material of the negative electrode layer 4 is a composite material, the negative electrode active material preferably contains at least one material selected from the group consisting of metal powder, alloy powder, glass powder, graphite, hard carbon, complex oxides, and metal oxides. Examples of the glass powder include oxide-based glass and sulfide-based glass. Examples of the complex oxide include P2-Na 0.66 [Li 0.22 Ti 0.78 ]O2 or Li4Ti5O 12 Examples of metal oxides include SnO, Bi2O3, and Fe2O3. Carbon materials such as graphite and hard carbon are difficult to adhere to the solid electrolyte layer 2, making it difficult to form an ion conduction path between the solid electrolyte layer 2 and the anode layer 4. Even in such cases, in this embodiment, the solid electrolyte layer 2 and the anode layer 4 can be adhered to each other via the alkali metal layer 3, thereby achieving good battery characteristics.

[0042] As the binder, for example, polyacrylic acid or sodium carboxymethyl cellulose (CMC-Na) can be used.

[0043] The conductive additive may be, for example, conductive carbon, such as acetylene black or carbon black.

[0044] solid electrolyte layer; In this embodiment, the solid electrolyte layer 2 is formed from an alkali metal ion-conductive oxide. Examples of alkali metal ion-conductive oxides include beta-alumina and NASICON crystals, which have excellent alkali metal ion conductivity. Such oxide solid electrolytes are difficult to soften and flow by heat treatment, making it difficult to adhere them to the anode layer 4 and forming an ion conduction path between the solid electrolyte layer 2 and the anode layer 4. Even in such cases, in this embodiment, the solid electrolyte layer 2 and the anode layer 4 can be adhered to each other via the alkali metal layer 3, thereby achieving good battery characteristics. In the following, preferred materials will be shown when sodium ions are used as an example of alkali metal ions used as carrier ions.

[0045] Beta alumina exists in two crystal forms: β-alumina (theoretical composition: Na2O·11Al2O3) and β"-alumina (theoretical composition: Na2O·5.3Al2O3). β"-alumina is a metastable substance, so it is usually used with Li2O or MgO added as a stabilizer. β"-alumina has a higher sodium ion conductivity than β-alumina, so it is preferable to use β"-alumina alone or a mixture of β"-alumina and β-alumina. Li2O-stabilized β"-alumina (Na 1.7 Li 0.3 Al 10.7 O 17 ) or MgO-stabilized β”-alumina ((Al 10.32 Mg 0.68 O 16 )(Na 1.68 It is more preferable to use O).

[0046] NASICON crystals include Na3Zr2Si2PO 12 , Na 3.2 Zr 1.3 Si 2.2 P 0.7 O 10.5 , Na3Zr 1.6 Ti 0.4 SiPO 12 , Na3Hf2Si2PO 12, Na 3.4 Zr 0.9 Hf 1.4 Al 0.6 Si 1.2 P 1.8 O 12 , Na3Zr 1.7 Nb 0.24 SiPO 12 , Na 3.6 Ti 0.2 Y 0.7 Si 2.8 O9, Na3Zr 1.88 Y 0.12 SiPO 12 , Na 3.12 Zr 1.88 Y 0.12 SiPO 12 , Na 3.6 Zr 0.13 Yb 1.67 Si 0.11 P 2.9 O 12 etc., especially Na 3.12 Zr 1.88 Y 0.12 SiPO 12 is preferred because it has excellent sodium ion conductivity.

[0047] The solid electrolyte layer 2 can be produced by mixing raw material powders, molding the mixed raw material powders, and then firing the molded product. For example, the solid electrolyte layer 2 can be produced by forming a green sheet from the raw material powders into a slurry, and then firing the green sheet. Alternatively, the solid electrolyte layer 2 may be produced by a sol-gel method.

[0048] The average particle size of the solid electrolyte powder used as the raw material powder is preferably 0.05 μm or more and 3 μm or less, more preferably 0.05 μm or more and less than 1.8 μm, even more preferably 0.05 μm or more and 1.5 μm or less, and particularly preferably 0.1 μm or more and 1.2 μm or less. If the average particle size of the solid electrolyte powder is too small, it is difficult to uniformly mix it with the positive electrode active material precursor powder. This may result in reduced ionic conductivity due to moisture absorption or carbonation, or may promote excessive reaction with the positive electrode active material precursor powder. As a result, the internal resistance of the positive electrode material layer tends to increase, and the voltage characteristics and charge / discharge capacity tend to decrease. On the other hand, if the average particle size of the solid electrolyte powder is too large, the softening and flow of the positive electrode active material precursor powder is significantly hindered, resulting in poor smoothness of the resulting positive electrode material layer, reduced mechanical strength, and increased internal resistance.

[0049] Positive electrode layer; The positive electrode layer 26 is not particularly limited as long as it contains a positive electrode active material capable of absorbing and releasing alkali ions and functions as the positive electrode layer 26. In the following, a material suitable for use when sodium ions are used as an example of alkali metal ions used as carrier ions will be described.

[0050] Examples of active material crystals that function as positive electrode active materials include sodium transition metal phosphate crystals containing Na, M (M is at least one transition metal element selected from Cr, Fe, Mn, Co, V, and Ni), P, and O. Specific examples include Na2FeP2O7, NaFePO4, Na3V2(PO4)3, Na2NiP2O7, Na 3.64 Ni 2.18 (P2O7)2, Na3Ni3(PO4)2(P2O7), Na2CoP2O7, Na 3.64 Co 2.18 (P2O7)2, etc. The sodium transition metal phosphate crystal is preferred because it has a high capacity and excellent chemical stability. Among them, triclinic crystals belonging to the space group P1 or P-1, especially those of the general formula Na x M y P2O zA crystal represented by the formula (1.2≦x≦2.8, 0.95≦y≦1.6, 6.5≦z≦8) is preferred because it has excellent cycle characteristics. Other active material crystals that act as positive electrode active materials include NaCrO2, Na 0.7 MnO2, NaFe 0.2 Mn 0.4 Ni 0.4 Examples of such crystals include layered sodium transition metal oxide crystals such as O. The positive electrode active material crystals contained in the positive electrode layer may be a single phase in which only one type of crystal is precipitated, or a mixed phase in which multiple types of crystals are precipitated.

[0051] The positive electrode layer 26 may contain the same binder and conductive additive as the negative electrode layer 4.

[0052] The positive electrode layer 26 may be formed, for example, by firing an active material precursor powder such as glass powder. By firing the active material precursor powder, active material crystals are precipitated, and these active material crystals act as the positive electrode active material.

[0053] current collector layer; The material for the current collector layer 5 and the current collector layer 27 is not particularly limited, but may be a metal material such as aluminum, titanium, silver, copper, stainless steel, or an alloy thereof. The above metal materials may be used alone or in combination.

[0054] The method for forming the current collector layer 5 and the current collector layer 27 is not particularly limited, and examples thereof include physical vapor deposition methods such as vapor deposition or sputtering, and chemical vapor deposition methods such as thermal CVD, MOCVD, and plasma CVD. Other methods for forming the current collector layer 5 and the current collector layer 27 include plating, a sol-gel method, and a liquid phase film formation method using spin coating. However, forming the current collector layer 5 and the current collector layer 27 by a sputtering method is preferred because it provides excellent adhesion.

[0055] [Manufacturing method] (Electricity storage device according to second embodiment) An example of a method for manufacturing the all-solid-state battery 20 as the electricity storage device according to the second embodiment will be described below. When manufacturing the electricity storage device member 1 alone, the steps of forming the positive electrode layer 26 and the current collector layer 27 may be omitted.

[0056] Figures 4(a) and 4(b) are front cross-sectional views for explaining an example of a method for manufacturing the electricity storage device according to the second embodiment. Figures 5(a) and 5(b) are front cross-sectional views for explaining an example of a method for manufacturing the electricity storage device according to the second embodiment.

[0057] First, as shown in FIG. 4(a), a solid electrolyte layer 2 is prepared. Next, a positive electrode layer 26 is formed on the solid electrolyte layer 2. This results in a positive electrode layer-solid electrolyte layer member 32A. Next, a current collector layer 27 is formed on the positive electrode layer 26 of the positive electrode layer-solid electrolyte layer member 32A. Meanwhile, as shown in FIG. 4(b), a current collector layer 5 is prepared. Next, a negative electrode layer 4 is formed on the current collector layer 5.

[0058] Next, as shown in FIG. 5(a), an alkali metal layer 3 is laminated on the solid electrolyte layer 2 of the cathode layer-solid electrolyte layer member 32A. Specifically, a separately prepared alkali metal layer 3 is pressure-bonded to the surface of the solid electrolyte layer 2. As described above, the alkali metal layer 3 has high flexibility, so the shape of the alkali metal layer 3 can be suitably conformed to the surface shape of the solid electrolyte layer 2. This makes it possible to easily form an ion conduction path. The alkali metal layer 3 may be formed on the solid electrolyte layer 2 by, for example, sputtering or vacuum deposition. In this case, the shape of the alkali metal layer 3 can also be conformed to the surface shape of the solid electrolyte layer 2.

[0059] Next, as shown in FIG. 5(b), the alkali metal layer 3 provided on the cathode layer-solid electrolyte layer member 32A and the anode layer 4 are pressure-bonded. Next, the cathode layer-solid electrolyte layer member 32A, the alkali metal layer 3, and the anode layer 4 are laminated together and an annealing treatment is performed. This causes the alkali metal contained in the alkali metal layer 3 to diffuse into the anode layer 4. In this manner, an all-solid-state battery 20 is obtained.

[0060] Here, the method for laminating the positive electrode layer-solid electrolyte layer member 32A, the alkali metal layer 3, and the negative electrode layer 4 is not limited to the above. Another example of the lamination method will be described below.

[0061] Figures 6(a) and 6(b) are front cross-sectional views for explaining an example of a method for manufacturing the electricity storage device according to the second embodiment. Figures 7(a) and 7(b) are front cross-sectional views for explaining an example of a method for manufacturing the electricity storage device according to the second embodiment.

[0062] First, as shown in FIG. 6(a), an alkali metal layer 3 is laminated on the anode layer 4. This allows the shape of the alkali metal layer 3 to suitably follow the surface shape of the anode layer 4. This makes it possible to easily form an ion conduction path. Next, as shown in FIG. 6(b), the alkali metal layer 3 provided on the anode layer 4 and the solid electrolyte layer 2 of the cathode layer-solid electrolyte layer member 32A are pressure-bonded. In this manner, an all-solid-state battery 20 is obtained.

[0063] As another example, first, as shown in Fig. 7(a), an alkali metal thin film 33B is laminated on the solid electrolyte layer 2 of a positive electrode layer-solid electrolyte layer member 32A. On the other hand, as shown in Fig. 7(b), an alkali metal thin film 33A is laminated on the negative electrode layer 4. The alkali metal thin films 33A and 33B can be formed by, for example, sputtering or vacuum deposition.

[0064] Next, as shown in FIG. 7(c), the alkali metal thin film 33A stacked on the anode layer 4 and the alkali metal thin film 33B stacked on the cathode layer-solid electrolyte layer member 32A are pressure-bonded and integrated to form the alkali metal layer 3. In this case, the shape of the alkali metal layer 3 can be made to suitably follow the surface shapes of both the anode layer 4 and the solid electrolyte layer 2. This makes it possible to easily increase the ion conduction paths. In this manner, an all-solid-state battery 20 is obtained.

[0065] An example of a method for manufacturing an all-solid-state battery as an electricity storage device having an electricity storage device member 11 according to a modified example of the first embodiment will be described below.

[0066] 8(a) and 8(b) are front cross-sectional views illustrating an example of a method for manufacturing an electricity storage device using an electricity storage device member according to a modified example of the first embodiment.

[0067] First, as shown in Fig. 8(a), a first metal layer 34A made of a metal that does not absorb and release alkali metal ions is formed. Next, a second metal layer 34B made of a metal that can absorb and release alkali metal ions is laminated on the first metal layer 34A. Next, the laminate of the first metal layer 34A and the second metal layer 34B is annealed to alloy them, thereby forming the negative electrode layer 14 as shown in Fig. 8(b).

[0068] On the other hand, a cathode layer-solid electrolyte layer component 32A is prepared in the same manner as shown in Fig. 4(a). Next, the cathode layer-solid electrolyte layer component 32A, the alkali metal layer 3, and the anode layer 14 are laminated in the same manner as shown in Figs. 5(a) and 5(b), 6(a) and 6(b), or 7(a) and 7(b).

[0069] Next, an annealing treatment is performed on the stacked cathode layer-solid electrolyte layer member 32A, alkali metal layer 3, and anode layer 14. This causes the alkali metal contained in the alkali metal layer 3 to diffuse into the anode layer 14. In this manner, an all-solid-state battery having an electricity storage device member 11 is obtained.

[0070] [Example] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0071] Example 1 (a) Preparation of cathode layer-solid electrolyte layer component The active material precursor, 2Na2O-Fe2O3-2P2O5 glass, was prepared by melting. The resulting 2Na2O-Fe2O3-2P2O5 glass was coarsely pulverized in a ball mill and then wet-pulverized in a planetary ball mill to produce glass powder with a D50 of 0.6 μm.

[0072] β″-alumina (manufactured by Ionotec) was coarsely pulverized in a ball mill and then air classified to produce a solid electrolyte powder with a D50 of 1.7 μm.

[0073] Acetylene black (SuperC65, manufactured by Timcal) was used as the conductive additive in the positive electrode layer. A glass powder, which serves as the active material precursor, a solid electrolyte powder, and the conductive additive were mixed in a weight ratio of 72:25:3 to obtain a mixture. Next, 10 parts by weight of polypropylene carbonate was added as a binder to the obtained mixture, relative to 100 parts by weight of the mixture, and N-methyl-2-pyrrolidone was further added as a solvent to form a paste.

[0074] On the other hand, a β″-alumina plate (manufactured by Ionotec) was used for the solid electrolyte layer. The paste was applied onto the solid electrolyte layer and dried. The amount of the positive electrode active material supported was 4.5 mg / cm. 2 The paste was applied so that the amount of the positive electrode active material supported was 4.5 mg / cm 2 When the capacity per unit area of ​​the formed positive electrode layer is 0.44 mAh / cm 2 Next, the product was baked in a mixed gas of N2 / H2=96 / 4 v / v% at 500°C for 30 minutes to prepare a positive electrode layer-solid electrolyte layer member.

[0075] Next, a current collector layer made of Al was formed on the surface of the positive electrode layer of the positive electrode layer-solid electrolyte layer member using a sputtering device. The current collector layer had a thickness of 500 nm.

[0076] (b) Preparation of the negative electrode layer Hard carbon (AT Electrode, "BELLFINE LN0001") was used as the negative electrode active material. Acetylene black (Timcal, "SuperC65") was used as the conductive additive. Carboxymethyl cellulose sodium (Daicel FineChem) was used as the binder. The negative electrode active material, conductive additive, and binder were mixed in a weight ratio of 80:10:10 to obtain a mixture. Next, pure water was added to the obtained mixture, and the mixture was mixed using a rotation-revolution mixer to form a slurry. Next, the obtained slurry was coated on an Al foil with a thickness of 18 μm. The amount of negative electrode active material supported was 8 mg / cm. 2 The thickness of the slurry was set to 300 μm so that the amount of the negative electrode active material supported was 8 mg / cm 2 When the capacity per unit area of ​​the formed negative electrode layer is 2.4 mAh / cm 2 Next, the slurry was dried at 70°C to obtain a dried mixture. Next, the dried mixture was placed on an Al foil and pressed with a pair of rotating rollers to obtain an electrode sheet. Next, the obtained electrode sheet was punched out into a circular sheet with a diameter of 11 mm using an electrode punching machine. Next, the resultant was dried under reduced pressure at 140°C for 6 hours to produce a circular negative electrode layer.

[0077] (c) Fabrication of all-solid-state batteries Metallic sodium foil was obtained by rolling and molding metallic sodium. Next, the obtained metallic sodium foil was punched into a circle with a diameter of 11 mm using an electrode punching machine. Next, the circular metallic sodium foil was attached to the surface of the negative electrode layer. This resulted in a laminate of metallic sodium foil as an alkali metal layer and a negative electrode layer. Note that the amount of metallic sodium supported was 10 mg / cm. 2 Next, the metallic sodium layer attached on the negative electrode layer was pressure-bonded to the surface of the solid electrolyte layer of the positive electrode layer-solid electrolyte layer member. In this way, an all-solid-state battery was obtained.

[0078] (d) Preparation of test battery The all-solid-state battery obtained by the above steps was placed on the bottom cover of a coin cell, and then the top cover was placed on top to prepare a CR2032 test battery. The formation of the metallic sodium layer in step (c) and step (d) were carried out in an argon atmosphere with a dew point of -70°C or lower.

[0079] Example 2 An all-solid-state battery and a test battery were fabricated in the same manner as in Example 1, except that in step (c), the metallic sodium layer was formed by vacuum deposition.

[0080] Specifically, a metallic sodium thin film was formed on the surface of the solid electrolyte layer of the cathode layer-solid electrolyte layer member by vacuum deposition. The metallic sodium thin film was circular with a diameter of 11 mm and had a metallic sodium loading of 0.25 mg / cm. 2 It was decided.

[0081] On the other hand, a metallic sodium thin film was also formed by vacuum deposition on the surface of the negative electrode layer formed in the same manner as in Example 1. The metallic sodium thin film was circular with a diameter of 11 mm, and the amount of metallic sodium supported was 0.25 mg / cm. 2 Thereafter, the metallic sodium thin film formed on the negative electrode layer and the metallic sodium thin film formed on the positive electrode layer-solid electrolyte layer member were pressure-bonded and integrated to form a metallic sodium layer, and an all-solid-state battery was obtained. Note that in Example 2, the metallic sodium loading amount was 0.5 mg / cm of the total loading amount of metallic sodium in each of the metallic sodium thin films. 2 In Example 2 as well, the formation of the metallic sodium layer was carried out in an argon atmosphere with a dew point of −70° C. or lower. Thereafter, a test battery was fabricated in the same manner as in Example 1.

[0082] Example 3 The amount of metallic sodium loaded is 1 mg / cm 2 (0.5mg / cm 2 +0.5mg / cm 2 ) All-solid-state batteries and test batteries were fabricated in the same manner as in Example 2.

[0083] Example 4 Metallic sodium loading of 5 mg / cm 2 Except for this, an all-solid-state battery and a test battery were fabricated in the same manner as in Example 1.

[0084] Example 5 Stannous pyrophosphate (Sn2P2O7) was used as the main raw material, and raw material powder was prepared using various oxides, phosphate raw materials, carbonate raw materials, metallic Sn powder raw material as a reducing agent, carbon raw material, etc., so that the composition was 72 mol% SnO and 28 mol% P2O5. The raw material powder was then placed in a quartz crucible and melted by heating at 950°C for 40 minutes in an electric furnace under a nitrogen atmosphere. This melt was then molded into a film-like glass. The resulting glass was coarsely pulverized in a ball mill and air-classified to produce a negative electrode active material powder with an average particle size of 2 μm. Powder X-ray diffraction analysis of the resulting negative electrode active material powder revealed that it was amorphous, with no crystals detected.

[0085] Next, the negative electrode active material powder, the conductive additive, and the binder were mixed in a weight ratio of 80:5:15 to obtain a mixture. The conductive material and the binder used were the same as those used in Example 1. Next, pure water was added to the obtained mixture, and the mixture was mixed using a rotation-revolution mixer to form a slurry. Thereafter, the amount of metallic sodium supported was adjusted to 3 mg / cm. 2 Except for this, an all-solid-state battery and a test battery were fabricated in the same manner as in Example 1.

[0086] Example 6 A Cu foil was electroplated in a sulfuric acid bath containing stannous sulfate, sulfuric acid, and a semi-bright additive. Semi-bright plating can form a film with lower stress than bright plating. In the sulfuric acid bath, the stannous sulfate was 20 g / L and the sulfuric acid was 150 g / L. This resulted in the formation of a Sn layer on the Cu foil, yielding an electrode sheet. In Example 6, the negative electrode active material was Sn. The Cu foil had a thickness of 20 μm, the Sn layer had a thickness of 7 μm, and the Sn loading was 5 mg / cm. 2The amount of Sn supported as the negative electrode active material was 5 mg / cm 2 When the capacity per unit area of ​​the formed negative electrode layer is 4.5 mAh / cm 2 Next, the obtained electrode sheet was punched out into a circular sheet with a diameter of 11 mm using an electrode punching machine. Next, it was dried under reduced pressure at 120°C for 6 hours to prepare a circular negative electrode layer. Thereafter, the amount of metallic sodium supported was adjusted to 3 mg / cm. 2 Except for this, an all-solid-state battery and a test battery were fabricated in the same manner as in Example 1.

[0087] (Comparative Example) An all-solid-state battery and a test battery were fabricated in the same manner as in Example 1, except that the negative electrode layer and positive electrode layer-solid electrolyte layer members fabricated in the same manner as in Example 1 were directly bonded together without a metallic sodium layer therebetween.

[0088] (Charge / discharge test) The test batteries prepared in Examples 1 to 6 and Comparative Example were subjected to CC (constant current) charging from the open circuit voltage to 5 V at 30° C. Then, CC discharging was performed from 5 V to 2 V at 30° C. The C rate during charging and discharging was 0.05 C.

[0089] The results of the charge / discharge characteristics are shown in Table 1. In the "Charge / Discharge Results" section of Table 1, those that were able to be charged / discharged are marked with an O, and those that were not are marked with an X. "Discharge voltage" refers to the average operating voltage at the time of the first discharge.

[0090] [Table 1]

[0091] As shown in Table 1, in Examples 1 to 6, charging and discharging was possible at 2.57 V or higher. On the other hand, in the comparative example in which the metallic sodium layer was not formed, the battery did not work. [Explanation of symbols]

[0092] 1...Electricity storage device components 2...Solid electrolyte layer 3...Alkali metal layer 4...Anode layer 4a...Outer main surface 5...Current collector layer 11...Electricity storage device components 14...Anode layer 14a...Outer main surface 20…All-solid-state battery 26...Positive electrode layer 27...Current collector layer 32A...Positive electrode layer-solid electrolyte layer member 33A...Alkali metal thin film 33B...Alkali metal thin film 34A...first metal layer 34B...Second metal layer

Claims

1. a solid electrolyte layer containing an alkali metal ion conductive solid electrolyte; an alkali metal layer made of metallic sodium and laminated on the solid electrolyte layer; a negative electrode layer laminated on the alkali metal layer and containing a material capable of absorbing and releasing alkali metal ions; A member for an electricity storage device comprising:

2. 2. The member for an electric storage device according to claim 1, wherein the negative electrode active material contained in the negative electrode layer is a compound containing at least one of a metal and an alloy and an alkali metal element of the same type as the alkali metal element contained in the alkali metal layer.

3. 3. The electricity storage device member according to claim 2, wherein at least a portion of the negative electrode layer is made of an alloy containing the same type of alkali metal element as the alkali metal element contained in the alkali metal layer.

4. The electricity storage device member according to claim 2 or 3, wherein the alkali metal contained in the alkali metal layer is diffused into the negative electrode layer.

5. The member for an electricity storage device according to any one of claims 2 to 4, wherein the negative electrode active material is a compound containing Na.

6. 6. The member for an electric storage device according to claim 2, wherein the negative electrode active material contains at least one element selected from the group consisting of Sn, Bi, Sb, and Pb.

7. The electricity storage device member according to any one of claims 1 to 6, wherein the negative electrode layer contains a binder.

8. The electricity storage device member according to any one of claims 1 to 7, wherein the solid electrolyte layer contains an oxide.

9. The electricity storage device member according to any one of claims 1 to 8, wherein the alkali metal layer has a thickness of 5 nm or more and 500 µm or less.

10. The member for an electricity storage device according to any one of claims 1 to 9, The power storage device further comprises a positive electrode layer stacked on the solid electrolyte layer so as to sandwich the solid electrolyte layer together with the alkali metal layer.

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