All-solid-state battery

Abstract

As a problem, the main object of the present disclosure is to provide an all-solid battery in which occurrence of short circuit is suppressed. In the present disclosure, the problem is solved by providing an all-solid battery having a negative electrode having at least a negative electrode current collector, a positive electrode, and a solid electrolyte layer disposed between the negative electrode and the positive electrode, a protective layer being disposed between the negative electrode current collector and the solid electrolyte layer, the protective layer containing Mg-containing particles and a polymer, the Mg-containing particles containing at least Mg.

Description

Technical Field

[0001] This disclosure relates to all-solid-state batteries. Background Technology

[0002] All-solid-state batteries are batteries with a solid electrolyte layer between the positive and negative electrodes. Compared with liquid batteries with electrolytes containing flammable organic solvents, they have the advantage of being easier to simplify safety devices.

[0003] For example, Patent Document 1 discloses an all-solid-state battery in which a protective layer is provided between a negative electrode active material layer and a solid electrolyte layer, the protective layer comprising a composite metal oxide represented by Li-M-O (M is at least one metal element selected from Mg, Au, Al and Sn).

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-184407 Summary of the Invention

[0007] From the viewpoint of improving the safety of all-solid-state batteries, it is desirable to suppress the occurrence of short circuits. This disclosure was made in view of the above-mentioned actual situation, and its main objective is to provide an all-solid-state battery that suppresses the occurrence of short circuits.

[0008] To address the aforementioned issues, this disclosure provides an all-solid-state battery comprising: a negative electrode having at least a negative current collector; a positive electrode; and a solid electrolyte layer disposed between the negative electrode and the positive electrode, wherein a protective layer is disposed between the negative current collector and the solid electrolyte layer, the protective layer comprising: Mg-containing particles containing at least Mg; and a polymer.

[0009] According to this disclosure, an all-solid-state battery that suppresses the occurrence of short circuits is formed by providing a protective layer containing Mg particles and polymers between the negative electrode current collector and the solid electrolyte layer.

[0010] In the above disclosure, a negative electrode active material layer containing a negative electrode active material may be disposed between the negative electrode current collector and the protective layer, wherein the negative electrode active material may be at least one of elemental Li and Li alloy.

[0011] In the above disclosure, the negative current collector and the protective layer can be in direct contact.

[0012] In the above disclosure, the Mg-containing particles may contain Li.

[0013] In the above disclosure, the Mg-containing particles may also not contain Li.

[0014] In the above disclosure, the average particle size (D) of the Mg-containing particles is... 50 It can be above 800nm ​​and below 10μm.

[0015] In the above disclosure, the thickness of the protective layer can be more than 5 μm and less than 100 μm.

[0016] In the above disclosure, the all-solid-state battery may also include a restraint fixture that applies restraint pressure to the positive electrode, the solid electrolyte layer, and the negative electrode along the thickness direction, wherein the restraint pressure applied by the restraint fixture is 20 MPa or less.

[0017] In this disclosure, an all-solid-state battery is achieved that can suppress the occurrence of short circuits. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view illustrating an example of an all-solid-state battery in this disclosure.

[0019] Figure 2 This is a schematic cross-sectional view showing another example of an all-solid-state battery in this disclosure.

[0020] Explanation of reference numerals in the attached figures

[0021] 1…Negative electrode active material layer

[0022] 2… Negative current collector

[0023] 3… Positive electrode active material layer

[0024] 4…Positive current collector

[0025] 5… Solid electrolyte layer

[0026] 6…protective layer

[0027] 10… All-solid-state batteries Detailed Implementation

[0028] The all-solid-state battery of this disclosure will now be described in detail.

[0029] Figure 1 This is a schematic cross-sectional view illustrating an example of an all-solid-state battery in this disclosure. Figure 1 The all-solid-state battery 10 shown has a negative electrode AN, a positive electrode CA, and a solid electrolyte layer 5. The negative electrode AN has a negative active material layer 1 and a negative current collector 2; the positive electrode CA has a positive active material layer 3 and a positive current collector 4, and the solid electrolyte layer 5 is disposed between the negative electrode AN and the positive electrode CA. Furthermore, in Figure 1In this process, a protective layer 6 is disposed between the negative electrode active material layer 1 and the solid electrolyte layer 5. The protective layer 6 contains: Mg-containing particles containing at least Mg; and a polymer. Furthermore, as... Figure 1 As shown, the protective layer 6 can also be considered as a component of the negative electrode AN.

[0030] Figure 2 This is a schematic cross-sectional view illustrating another example of an all-solid-state battery in this disclosure. (See diagram below.) Figure 2 As shown, the all-solid-state battery 10 may not have a negative electrode active material layer, and the negative electrode current collector 2 and the protective layer 6 are in direct contact. Furthermore, when... Figure 2 When the all-solid-state battery shown is charged, lithium is deposited between the negative electrode current collector 2 and the protective layer 6, which can yield... Figure 1 The negative electrode active material layer 1 (lithium deposition layer) is shown. That is, the all-solid-state battery in this disclosure can also be a battery that utilizes the deposition-dissolution reaction of metallic lithium.

[0031] According to this disclosure, by providing a protective layer containing Mg particles and polymers between the negative electrode current collector and the solid electrolyte layer, an all-solid-state battery that suppresses the occurrence of short circuits is achieved.

[0032] In Patent Document 1, in an all-solid-state battery utilizing the deposition-dissolution reaction of lithium metal as the negative electrode reaction, a protective layer containing a composite metal oxide (Li-M-O) is disposed between the negative electrode active material layer and the solid electrolyte layer. This protects the solid electrolyte from degradation caused by lithium metal and suppresses the interface resistance between the negative electrode active material layer and the solid electrolyte layer. Furthermore, in Patent Document 1, a protective layer containing a composite metal oxide is formed by vacuum evaporating a metal element (M) onto the negative electrode current collector and charging it to react with Li.

[0033] In this all-solid-state battery, which utilizes the deposition-dissolution reaction of lithium metal as the negative electrode reaction, the metal contained in the protective layer expands and contracts due to the insertion and extraction of Li. Therefore, in a protective layer like that in Patent Document 1, cracking is possible. When the protective layer cracks, a short circuit may occur at the crack. In contrast, the protective layer of this disclosure, because it contains a polymer, can suppress cracking of the protective layer. As a result, short circuits in the all-solid-state battery can be suppressed. Furthermore, the protective layer of this disclosure, like that in Patent Document 1, can suppress the interfacial impedance between the negative electrode active material layer and the solid electrolyte layer.

[0034] 1. Protective layer

[0035] The protective layer in this disclosure is a layer disposed between the negative electrode current collector and the solid electrolyte layer, as described later, and contains: Mg-containing particles containing at least Mg; and a polymer.

[0036] The particles contain at least Mg. These Mg-containing particles can be particles of elemental Mg or particles containing Mg and elements other than Mg. Examples of elements other than Mg include Li, and metals other than Li (including half-metals). Other examples of elements other than Mg include nonmetals such as O.

[0037] The particles can contain Mg, or they can be alloy particles containing Mg and metals other than Mg. The alloy particles are preferably alloys containing Mg as the main component. Examples of metals M other than Mg in the alloy particles include Li, Au, Al, and Ni. The alloy particles can contain one metal M or two or more metals M. Furthermore, the Mg-containing particles may or may not contain Li. In the former case, the alloy particles can be β-single-phase alloys containing Li and Mg.

[0038] Mg-containing particles can also be oxide particles containing both Mg and O. Examples of oxide particles include oxides of elemental Mg and composite metal oxides represented by Mg-M'-O (where M' is at least one of Li, Au, Al, and Ni). The oxide particles preferably contain at least Li as M'. M' may or may not contain a metal other than Li. In the former case, M' may be one or more metals other than Li. On the other hand, Mg-containing particles may not contain O.

[0039] Mg-containing particles can be primary particles or secondary particles formed by the aggregation of primary particles. Furthermore, the preferred average particle size (D) of the Mg-containing particles is... 50 The average particle size is small. This is because when the average particle size is small, the dispersibility of Mg-containing particles in the protective layer is improved, increasing the reaction sites with Li, which is effective in suppressing short circuits. The average particle size of Mg-containing particles (D) 50 For example, it can be 500 nm or larger, or even 800 nm or larger. On the other hand, the average particle size (D) of Mg-containing particles... 50 For example, it can be below 20μm, below 10μm, or below 5μm.

[0040] The proportion of Mg-containing particles in the protective layer is, for example, 50% by weight or more, 60% by weight or more, or 80% by weight or more. On the other hand, the above-mentioned proportion of Mg-containing particles is, for example, 99% by weight or less, or 90% by weight or less. Furthermore, the Mg-containing particles expand and contract due to the insertion and release of Li. In this respect, the Mg-containing particles can also be controlled as an active material. The protective layer preferably contains only Mg-containing particles as an active material, but it may also contain other active material particles. The proportion of Mg-containing particles in the protective layer relative to the total active material is, for example, 50% by weight or more, 70% by weight or more, or 90% by weight or more.

[0041] Examples of polymers (adhesives) include fluorinated adhesives and rubber-based adhesives. Examples of fluorinated adhesives include polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Examples of rubber-based adhesives include butadiene rubber (BR), acrylate butadiene rubber (ABR), and styrene-butadiene rubber (SBR).

[0042] The proportion of polymer in the protective layer is not particularly limited; for example, it may be 10% by weight or less, 5% by weight or less, 3% by weight or less, or 1% by weight or less. On the other hand, the proportion of polymer may be 0.1% by weight or more, for example.

[0043] The thickness of the protective layer is not particularly limited; for example, it can be 5 μm or more, or 15 μm or more. On the other hand, the thickness of the protective layer can be, for example, 100 μm or less, or 50 μm or less, or 30 μm or less. As a method for forming the protective layer, a method of applying an agent containing Mg particles, a polymer, and a dispersion medium and then drying it can be listed.

[0044] 2. Negative electrode

[0045] The negative electrode in this disclosure has at least a negative current collector. As described above, the negative electrode may or may not have a negative active material layer.

[0046] When the negative electrode has a negative electrode active material layer, the negative electrode active material layer preferably contains at least one of elemental Li and Li alloy as the negative electrode active material. Furthermore, in this disclosure, elemental Li and Li alloy are sometimes collectively referred to as Li-based active materials. When the negative electrode active material layer contains Li-based active materials, the Mg-containing particles in the protective layer may or may not contain Li.

[0047] For example, in an all-solid-state battery manufactured using Li foil or Li alloy foil as the negative electrode active material and Mg elemental particles as the Mg-containing particles, it is presumed that Mg elemental particles and Li alloy during the first discharge. On the other hand, in an all-solid-state battery manufactured without a negative electrode active material layer, using Mg elemental particles as the Mg-containing particles and using a Li-containing positive electrode active material, it is presumed that Mg elemental particles and Li alloy during the first charge.

[0048] In the negative electrode active material layer, as a Li-based active material, it may contain only one of elemental Li and Li alloy, or it may contain both elemental Li and Li alloy.

[0049] Li alloys are preferably alloys containing Li as the main component. Examples of Li alloys include Li-Au, Li-Mg, Li-Sn, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. A Li alloy may consist of only one element or two or more elements.

[0050] Examples of the shapes of Li-based active materials include foil and granules. Additionally, Li-based active materials can also be deposited metallic lithium. As mentioned above, the protective layer contains a polymer (binder), but the negative electrode active material layer may not contain a binder.

[0051] The thickness of the negative electrode active material layer is not particularly limited; for example, it can be 1 nm or more and 1000 μm or less, or it can be 1 nm or more and 500 μm or less.

[0052] In addition, materials that can be used as negative electrode current collectors include, for example, Cu, Ni, In, Al, and C. Shapes that can be used as negative electrode current collectors include, for example, foil, mesh, and porous structures.

[0053] 3. Positive electrode

[0054] The positive electrode in this disclosure preferably comprises a positive electrode active material layer and a positive electrode current collector. The positive electrode active material layer in this disclosure is a layer containing at least a positive electrode active material. In addition, the positive electrode active material layer may also contain at least one of a solid electrolyte, a conductive material, and a binder, as needed.

[0055] The positive electrode active material is not particularly limited if it has a higher reaction potential than the negative electrode active material; any positive electrode active material suitable for all-solid-state batteries can be used. The positive electrode active material may or may not contain lithium.

[0056] Examples of positive electrode active materials containing lithium include metallic lithium (Li), lithium alloys, lithium oxides, and other lithium compounds.

[0057] Li alloys are preferably alloys containing Li as the main component. Examples of Li alloys include Li-Au, Li-Mg, Li-Sn, Li-Si, Li-Al, Li-Ge, Li-Sb, Li-B, Li-C, Li-Ca, Li-Ga, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, Li-At, and Li-In.

[0058] Examples of lithium oxides include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active substances, Li4Ti5O 12 LiMn2O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4 and LiMn 1.5 Zn 0.5 Spinel-type active substances such as O4, and olivine-type active substances such as LiFePO4, LiMnPO4, LiNiPO4, and LiCoPO4.

[0059] Other lithium compounds that can be listed include LiCoN, Li₂SiO₃, Li₄SiO₄, lithium sulfide (Li₂S), and lithium polysulfides (Li₂S). x (2≤x≤8).

[0060] Examples of lithium-free positive electrode active materials include transition metal oxides such as V2O5 and MoO3; S-based active materials such as S and TiS2; Si-based active materials such as Si and SiO2; and lithium-storing intermetallic compounds such as Mg2Sn, Mg2Ge, Mg2Sb, and Cu3Sb.

[0061] Furthermore, a coating containing ion-conducting oxides can be formed on the surface of the positive electrode active material. This coating can suppress the reaction between the positive electrode active material and the solid electrolyte, thus creating an all-solid-state battery with excellent output characteristics. Examples of ion-conducting oxides include LiNbO3 and Li4Ti5O3. 12 Li3PO4.

[0062] The proportion of positive electrode active material in the positive electrode active material layer is, for example, 20% by weight or more, 30% by weight or more, or 40% by weight or more. On the other hand, the proportion of positive electrode active material is, for example, 80% by weight or less, 70% by weight or less, or 60% by weight or less.

[0063] Examples of conductive materials include carbon materials. Specific examples of carbon materials include acetylene black, Ketjen black, VGCF, and graphite. Regarding the solid electrolyte, the same applies as described in "4. Solid Electrolyte Layer". Regarding the binder, the same applies as described in "2. Negative Electrode Active Material Layer". Furthermore, the thickness of the positive electrode active material layer is, for example, 0.1 μm or more and 1000 μm or less.

[0064] In addition, materials that can be used as positive current collectors include, for example, Al, Ni, and C. Shapes that can be used as positive current collectors include, for example, foil, mesh, and porous structures.

[0065] 4. Solid electrolyte layer

[0066] The solid electrolyte layer in this disclosure is a layer containing at least a solid electrolyte. Additionally, the solid electrolyte layer may, if necessary, contain an adhesive.

[0067] Examples of solid electrolytes include inorganic solid electrolytes such as halide solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, and nitride solid electrolytes. Among these, sulfide solid electrolytes are particularly preferred.

[0068] The sulfide solid electrolyte preferably contains, for example, Li, X (X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S. Additionally, the sulfide solid electrolyte may also contain at least one of O and a halogen element. As for the shape of the solid electrolyte, granular form is an example.

[0069] Examples of sulfide solid electrolytes include Li₂S-P₂S₅, Li₂S-P₂S₅-LiI, Li₂S-P₂S₅-GeS₂, Li₂S-P₂S₅-Li₂O, Li₂S-P₂S₅-Li₂O-LiI, Li₂S-P₂S₅-LiI, Li₂S-SiS₂, Li₂S-SiS₂-LiI, Li₂S-SiS₂-LiBr, Li₂S-SiS₂-LiCl, Li₂S-SiS₂-B₂S₃-LiI, Li₂S-SiS₂-P₂S₅-LiI, Li₂S-B₂S₃, and Li₂S-P₂S₅-Z. m Sn (where m and n are positive numbers, and Z is any one of Ge, Zn, and Ga), Li₂S-GeS₂, Li₂S-SiS₂-Li₃PO₄, Li₂S-SiS₂-Li x MO y (Where x and y are positive numbers. M is any one of P, Si, Ge, B, Al, Ga, and In.)

[0070] Solid electrolytes can be glassy or have a crystalline phase. Examples of solid electrolyte shapes include particles. The average particle size (D) of a solid electrolyte... 50 For example, it is 0.01 μm or larger. On the other hand, the average particle size (D) of solid electrolytes... 50 For example, the thickness can be below 10 μm, or below 5 μm. The ionic conductivity of a solid electrolyte at 25 °C is, for example, 1 × 10⁻⁶. -4 For values ​​above S / cm, it can be 1×10 -3 S / cm or higher.

[0071] Regarding the adhesive, since the same information is described in "1. Protective Layer", it is omitted here. Additionally, the thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less.

[0072] 5. Other components

[0073] The all-solid-state battery of this disclosure may further include a restraining jig that applies restraining pressure to the positive electrode, the solid electrolyte layer, and the negative electrode along the thickness direction. Known jigs can be used as the restraining jig. The restraining pressure is, for example, 0.1 MPa or more, and can be 1 MPa or more. On the other hand, the restraining pressure is, for example, 50 MPa or less, 20 MPa or less, 15 MPa or less, and 10 MPa or less. The lower the restraining pressure, the more easily the restraining jig can be enlarged. On the other hand, the lower the restraining pressure, the easier it is for a short circuit to occur, but by providing the protective layer of this disclosure, the occurrence of short circuits can be suppressed.

[0074] 6. All-solid-state batteries

[0075] The type of all-solid-state battery disclosed herein is not particularly limited; typically, it is a lithium-ion battery. Furthermore, the all-solid-state battery in this disclosure can be a primary battery or a secondary battery, with a secondary battery being preferred. This is because it can be repeatedly charged and discharged, making it useful as, for example, a battery for automotive applications.

[0076] The all-solid-state battery disclosed herein can be a single cell or a stacked battery. The stacked battery can be a unipolar stacked battery (parallel-connected stacked battery) or a bipolar stacked battery (series-connected stacked battery). Examples of battery shapes include coin shape, laminate shape, cylindrical shape, and square shape.

[0077] Furthermore, this disclosure is not limited to the embodiments described above. The embodiments described above are examples. Any solution that has a substantially the same structure as the technical concept described in the claims of this disclosure and achieves the same effect is included within the technical scope of this disclosure, regardless of the solution.

[0078] Example

[0079] [Example 1]

[0080] (Formation of the protective layer)

[0081] Heptane, a heptane solution containing 5% by weight of butadiene rubber, and Mg particles (elemental Mg, average particle size 10 μm, manufactured by EAM Japan Co., Ltd.) were added to a PP (polypropylene) container. The mixture was stirred for 30 seconds using an ultrasonic dispersion device (ESEMT UH-50). The container was then vibrated for 30 minutes using an oscillator (Shibata Scientific Co., Ltd., TTM-1). This prepared a protective layer mixture. The mixture was applied to a substrate (Al foil) using a scraper method with an applicator. It was then dried on a hot plate at 100°C for 30 minutes. This yielded a protective layer with a substrate. The thickness of the protective layer was 15 μm.

[0082] (Making the negative electrode)

[0083] A Li foil was placed on the negative current collector (Cu foil) as the negative electrode active material, and then pressed at 100 MPa. This yielded a negative electrode with both a negative current collector and a negative electrode active material layer.

[0084] (The production of the positive electrode)

[0085] The positive electrode active material (elemental sulfur), sulfide (P2S5), and binder (VGCF) were weighed in a weight ratio of S:P2S5:VGCF = 52.3:19.2:28.3. They were mixed in an agate mortar for 15 minutes to obtain a raw material mixture. The raw material mixture was then placed in a 45 mL container (made of ZrO2) of a planetary ball mill, followed by ZrO2 balls (Φ = 4 mm, 96 g), and the container was completely sealed. The container was mounted on a planetary ball mill (Frychu P7) and mechanically ground for a total of 48 hours, repeatedly rotating at 510 rpm for 1 hour, stopping for 15 minutes, and then mechanically grinding in reverse rotation (510 rpm) for 1 hour, stopping for 15 minutes. This yielded the positive electrode mixture.

[0086] A solution of mesitylene and SBR containing 5% by weight was added and shaken for 3 minutes using an oscillator (Shibata Scientific Co., Ltd., TTM-1), followed by mixing for 30 seconds using an ultrasonic dispersion device (Esemte UH-50). A positive electrode mixture was then added, and the mixture was stirred for 30 seconds using the ultrasonic dispersion device, followed by shaking for 3 minutes. This process was repeated twice. Then, using a coater with a pasting gap of 240 μm, the mixture was applied to the current collector (roughened Al foil). Afterward, it was dried in an electric furnace at 165°C for 30 minutes. This yielded a positive electrode having a positive current collector and a positive electrode active material layer.

[0087] (The fabrication of an all-solid-state battery)

[0088] A sulfide solid electrolyte (Li2S-P2S5 solid electrolyte containing LiI-LiBr), a binder (heptane solution containing 5% by weight of ABR), and a dispersion medium (butyl butyrate) were added to a PP container. The mixture was then stirred using an ultrasonic dispersion device for 30 seconds, vibrated for 3 minutes, and then stirred again using an ultrasonic dispersion device for 30 seconds. This yielded a mixture for the solid electrolyte layer. The mixture was then applied to a substrate (Al foil) using a doctor blade method with a coater. Subsequently, it was dried in an electric furnace at 150°C for 30 minutes. This resulted in a transfer component having a substrate and a solid electrolyte layer.

[0089] A positive electrode and a transfer component are laminated with a positive active material layer and a solid electrolyte layer in contact, and pressed at 600 MPa. The substrate (Al foil) is then peeled off to obtain laminate 1. Next, a negative electrode and a protective layer with a substrate are laminated with a negative active material layer and a protective layer in contact, and pressed at 100 MPa. The substrate is then peeled off to obtain laminate 2. Laminate 1 and laminate 2 are then laminated with a solid electrolyte layer and a protective layer in contact, and pressed at 100 MPa to obtain an electrode body. This electrode body is then encapsulated in a laminated film and restrained at 10 MPa using a restraint member. Thus, an all-solid-state battery is fabricated.

[0090] [Example 2]

[0091] A solid-state battery was fabricated in the same manner as in Example 1, except that Mg particles with an average particle size of 800 nm were used.

[0092] [Comparative Example 1]

[0093] Instead of a protective layer containing Mg particles and a binder, a protective layer containing Au (20 nm thick) was formed. Specifically, in the fabrication of the transfer component, Au was deposited by sputtering onto the surface of the solid electrolyte layer on the opposite side of the substrate to create the protective layer. A completely solid-state battery was fabricated in the same manner as in Example 1, except that the transfer component was used.

[0094] [Comparative Example 2]

[0095] Except for the absence of a protective layer, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0096] [Comparative Example 3]

[0097] Except that LiMg alloy foil was used as the negative electrode active material layer and no protective layer was formed, an all-solid-state battery was fabricated in the same manner as in Example 1.

[0098] [evaluate]

[0099] (Charge / Discharge Test)

[0100] For the all-solid-state batteries prepared in Examples 1, 2, and Comparative Examples 1-3, charge-discharge tests were performed as follows. First, they were discharged to 1.5V at a constant current-constant voltage rate of 10 hours (0.1C). Then, they were charged to 3.0V at a 10-hour rate (0.1C). Since the slope of the charging curve changes when a short circuit occurs, the short-circuit capacity up to that point was defined as the short-circuit capacity, and the respective short-circuit capacities were measured.

[0101] (Impedance measurement)

[0102] Impedance measurements were performed on each solid-state battery before the aforementioned charge-discharge tests. The impedance of the half circle was calculated by fitting the data, and the charge transfer resistivity was thus determined. The voltage amplitude was set to 10mV and the frequency to 100kHz–1kHz as conditions for the impedance measurement.

[0103] (Li ratio determination)

[0104] The Li ratio (the ratio of Li atoms in the negative electrode layer and the protective layer to the total number of metal atoms) of the all-solid-state battery at full charge (SOC 100%) was calculated. The Li ratio was calculated using the same method as described in Japanese Patent Application Laid-Open No. 2020-184513. The results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As shown in Table 1, it was confirmed that Examples 1 and 2, compared to Comparative Examples 1-3, had a larger short-circuit capacity and suppressed the occurrence of short circuits. This is presumably because, in Examples 1 and 2, a highly flexible protective layer was obtained by using a polymer in addition to Mg-containing particles. Furthermore, it is presumed that, compared to Example 1, Example 2 had a smaller average particle size and more reaction sites with Li, thus further increasing the short-circuit capacity. In contrast, in Comparative Example 2, a short circuit occurred immediately. This is presumably because the restraint pressure in the experimental system was low, at 10 MPa, an environment prone to short circuits. In contrast, in Examples 1 and 2, by providing a protective layer containing Mg-containing particles and a polymer, short circuits were suppressed even in an environment with a low restraint pressure of 10 MPa. Additionally, it is suggested that the Li ratio at full charge is preferably 62.5% or more and 75% or less.

Claims

1. A full-solid battery having: a negative electrode having at least a negative electrode current collector; a positive electrode; and a solid electrolyte layer disposed between the negative electrode and the positive electrode, only a single layer, which is a protective layer containing Mg-containing particles and a polymer, is disposed between the negative electrode current collector and the solid electrolyte layer, the negative electrode current collector and the solid electrolyte layer are each in direct contact with the protective layer, the Mg-containing particles are particles of elemental Mg, the full-solid battery further has a restraining jig that imparts a restraining pressure to the positive electrode, the solid electrolyte layer, and the negative electrode in a thickness direction, the restraining pressure imparted by the restraining jig is 20 MPa or less.

2. The full-solid battery according to claim 1, wherein the protective layer has a thickness of 5 μm or more and 100 μm or less.

3. The full-solid battery according to claim 1 or 2, wherein the protective layer has a thickness of 5 μm or more and 100 μm or less. ​ ​ ​ ​ The average particle diameter D of the Mg-containing particles is 800 nm or more and 10 μm or less. 50 is 800 nm or more and 10 μm or less. ​ ​

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