Secondary battery system and method for manufacturing secondary battery

Abstract

To disclose a system capable of recovering a performance of a secondary battery in the case where the performance of the secondary battery is deteriorated.SOLUTION: A secondary battery system of the present disclosure, includes: a secondary battery; and a heating device. The secondary battery includes: a positive electrode; and a negative electrode. One or both of the positive electrode and the negative electrode, contain(s) an active material and a pelletization body. The active material contains a material of which a volume is changed in accordance with a charging and discharging power of the secondary battery. The pelletization body contains an inorganic solid electrolyte and alkaline metal-containing salt. An object heated by the heating device contains the alkaline metal-containing salt.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application discloses a secondary battery system and a method for manufacturing a secondary battery. [Background technology]

[0002] Patent Document 1 discloses an all-solid-state battery having a positive electrode active material layer and a negative electrode active material layer, in which one or both of the positive electrode active material layer and the negative electrode active material layer contain a predetermined amount of Li-containing salt, and the Li-containing salt contains tetrabutylammonium bis(trifluoromethanesulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-096541 A Summary of the Invention [Problem to be solved by the invention]

[0004] Some active materials contained in the positive and negative electrodes change in volume as the battery is charged and discharged. When the volume of the active material changes as the battery is charged and discharged, cracks or gaps are generated in the positive and negative electrodes, and the resistance of the battery is likely to increase. Such problems are particularly likely to occur when the positive and negative electrodes contain an inorganic solid electrolyte together with the active material. [Means for solving the problem]

[0005] The present application discloses the following aspects as means for solving the above problems. <Aspect 1> A secondary battery system comprising a secondary battery and a heating device, The secondary battery has a positive electrode and a negative electrode, One or both of the positive electrode and the negative electrode includes an active material and a granule, the active material includes a material whose volume changes with charging and discharging of the secondary battery, The granules contain an inorganic solid electrolyte and an alkali metal-containing salt, The object to be heated by the heating device includes the alkali metal-containing salt. Secondary battery system. <Aspect 2> A control device is provided. when it is determined that the performance of the secondary battery is equal to or lower than a certain level, the control device controls the heating by the heating device so that the temperature of the alkali metal-containing salt is equal to or higher than a melting point of the alkali metal-containing salt. 2. The secondary battery system of embodiment 1. <Aspect 3> when it is determined that the performance of the secondary battery exceeds a certain level, the control device controls the heating by the heating device so that the temperature of the alkali metal-containing salt is lower than the melting point of the alkali metal-containing salt. 3. A secondary battery system according to embodiment 2. <Aspect 4> A voltage measuring device is provided. The voltage measuring device measures a voltage of the secondary battery, The performance of the secondary battery is based on the voltage. The secondary battery system according to embodiment 2 or 3. <Aspect 5> A resistance measuring device is provided. The resistance measuring device measures the resistance of the secondary battery, The performance of the secondary battery is based on the resistance. The secondary battery system according to embodiment 2 or 3. <Aspect 6> The alkali metal-containing salt has a melting point of 100° C. or less. The secondary battery system according to any one of the first to fifth aspects. <Aspect 7> The positive electrode includes the active material and the granules, The active material contains S. The secondary battery system according to any one of the first to sixth aspects. <Aspect 8> The negative electrode includes the active material and the granules, The active material contains Si. The secondary battery system according to any one of the first to seventh embodiments. <Aspect 9> The inorganic solid electrolyte contains a sulfide. The secondary battery system according to any one of the first to eighth embodiments. <Aspect 10> The alkali metal-containing salt has a first cation and a second cation; the first cation is at least one selected from an ammonium ion, a phosphonium ion, a pyridinium ion, and a pyrrolidinium ion; The second cation is an alkali metal ion. The secondary battery system according to any one of embodiments 1 to 9. <Aspect 11> The alkali metal-containing salt has a first cation and a second cation; the first cation is a tetraalkylammonium ion; The second cation is an alkali metal ion. The secondary battery system according to any one of embodiments 1 to 10. <Aspect 12> The alkali metal-containing salt has at least one anion selected from a halogen ion, a halide ion, a hydrogen sulfate ion, a sulfonyl amide ion, and a complex ion containing H. The secondary battery system according to any one of embodiments 1 to 11. <Aspect 13> The alkali metal-containing salt has one or both of a first anion and a second anion; the first anion is one or both of a halide ion and a hydrogen sulfate ion; The second anion is a sulfonylamide anion. The secondary battery system according to any one of embodiments 1 to 12. <Aspect 14> A method for manufacturing a secondary battery, comprising the steps of: Obtaining granules containing an inorganic solid electrolyte and an alkali metal-containing salt; Mixing the granules with an active material to obtain an electrode mixture; and forming one of a positive electrode and a negative electrode using the electrode mixture; A manufacturing method comprising: Effect of the Invention

[0006] According to the secondary battery system of the present disclosure, even if cracks or gaps occur in the positive or negative electrodes due to volume changes in the active material accompanying charging and discharging of the secondary battery, causing a decrease in the performance of the secondary battery, the cracks or gaps can be repaired by liquefying and melting the alkali metal-containing salt through heating by a heating device, and therefore, for example, the resistance of the secondary battery can be maintained low. [Brief description of the drawings]

[0007] [Figure 1] 1 shows a schematic configuration of a secondary battery system. [Diagram 2] 1 shows an example of the morphology of a granule. [Diagram 3] 3 shows an example of a control flow in the secondary battery system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1. Secondary Battery System Hereinafter, an embodiment of the secondary battery system of the present disclosure will be described with reference to the drawings. As shown in FIG. 1, a secondary battery system 100 according to an embodiment includes a secondary battery 10 and a heating device 20. The secondary battery 10 includes a positive electrode 11 and a negative electrode 12. One or both of the positive electrode 11 and the negative electrode 12 include an active material and a granule. The active material includes a substance whose volume changes with charging and discharging of the secondary battery 10. The granule includes an inorganic solid electrolyte and an alkali metal-containing salt. An object heated by the heating device 20 includes the alkali metal-containing salt.

[0009] 1.1 Secondary battery The secondary battery 10 has a positive electrode 11 and a negative electrode 12. The secondary battery 10 may have an electrolyte layer 13 between the positive electrode 11 and the negative electrode 12. The secondary battery 10 may further have a configuration not shown. One or both of the positive electrode 11 and the negative electrode 12 includes an active material whose volume changes with charging and discharging, and a granule containing an inorganic solid electrolyte and an alkali metal-containing salt. That is, the positive electrode 11 may include a predetermined active material and a predetermined granule, the negative electrode 12 may include a predetermined active material and a predetermined granule, or both the positive electrode 11 and the negative electrode 12 may include a predetermined active material and a predetermined granule.

[0010] 1.1.1 Positive electrode 1, the positive electrode 11 may have a positive electrode active material layer 11a and a positive electrode current collector 11b in contact with the layer 11a. In this case, the positive electrode active material layer 11a may contain a predetermined active material and a predetermined granule.

[0011] The positive electrode active material layer 11a includes at least a positive electrode active material. The positive electrode active material layer 11a may include a granulated body described later. The positive electrode active material layer 11a may include an electrolyte or an alkali metal-containing salt other than the granulated body described later. The positive electrode active material layer 11a may include a conductive assistant and a binder. The positive electrode active material layer 11a may further include various additives. The content of each component in the positive electrode active material layer 11a may be appropriately determined according to the intended battery performance. For example, the content of the positive electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or 100% by mass or less, 95% by mass or less, or 90% by mass or less, based on the entire solid content of the positive electrode active material layer 11a being 100% by mass. Alternatively, the positive electrode active material layer 11a may contain a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of the positive electrode active material, optionally granules, optionally solid electrolyte other than the granules, optionally alkali metal-containing salt other than the granules, optionally conductive assistant, and optionally binder, with the remainder being voids or other components. The shape of the positive electrode active material layer 11a is not particularly limited, and may be, for example, a sheet-like positive electrode active material layer having a substantially flat surface. The thickness of the positive electrode active material layer 11a is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0012] The positive electrode active material may be any material known as a positive electrode active material for secondary batteries. For example, in the case of constructing a lithium ion secondary battery, the positive electrode active material may be a lithium-containing composite oxide (lithium cobalt oxide, lithium nickel oxide, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2, lithium manganate, spinel-based lithium compounds, etc.) or those containing S (single S, S compound), etc. may be adopted. The positive electrode active material may be one whose volume changes with charging and discharging, for example, one whose expansion rate is 5% or more (one whose volume changes by 5% or more when comparing before and after expansion). Among them, the positive electrode active material containing S has a large volume change with charging and discharging the secondary battery 10. That is, when the positive electrode 11 includes an active material whose volume changes with charging and discharging, and a granule containing an inorganic solid electrolyte and an alkali metal-containing salt, and the active material includes S, it is considered that the system 100 of the present disclosure can achieve a more remarkable effect. Only one type of positive electrode active material may be used alone, or two or more types may be used in combination. The positive electrode active material may be, for example, particulate, and the size is not particularly limited. The particles of the positive electrode active material may be solid particles, hollow particles, or particles having voids (porous particles). The particles of the positive electrode active material may be primary particles or secondary particles formed by agglomeration of a plurality of primary particles. The average particle diameter (D50) of the particles of the positive electrode active material may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. The average particle diameter (D50) is the particle diameter (median diameter) at an integrated value of 50% in a volume-based particle size distribution obtained by a laser diffraction / scattering method.

[0013] The surface of the positive electrode active material may be covered with a protective layer containing an ion-conductive oxide. That is, the positive electrode 11 may include a composite having a positive electrode active material and a protective layer provided on the surface thereof. This makes it easier to suppress the reaction between the positive electrode active material and a sulfide (e.g., a sulfide solid electrolyte described later). Examples of lithium ion conductive oxides include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12, Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, and Li2WO4. The coverage (area ratio) of the protective layer may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer may be, for example, 0.1 nm or more or 1 nm or more, and may be 100 nm or less, or 20 nm or less.

[0014] The granules include at least an inorganic solid electrolyte and an alkali metal-containing salt. As described later, the granules can be obtained by mixing an inorganic solid electrolyte and an alkali metal-containing salt. In the present application, the term "granules" refers to a particle in which at least an inorganic solid electrolyte and an alkali metal-containing salt are attached to each other, and the specific form is not particularly limited. The granules may be particles in which at least a part of the surface of the inorganic solid electrolyte particles is covered with an alkali metal-containing salt. The granules may also be secondary particles of an inorganic solid electrolyte and an alkali metal-containing salt. FIG. 2 shows an example of a cross-sectional shape of the granules. In FIG. 2, the part where the S-existing region and the F-existing region overlap (for example, the flattened particle in the center of the image) corresponds to the granules. The size of the granules is not particularly limited, and may be any size that can be contained in the positive electrode 11 or the negative electrode 12. When the inorganic solid electrolyte and the alkali metal-containing salt form the granules, the alkali metal-containing salt is disposed near the inorganic solid electrolyte in the secondary battery. As a result, even if a volume change occurs in the active material as the secondary battery is charged and discharged, and this volume change causes cracks or gaps in the inorganic solid electrolyte, the alkali metal-containing salt adjacent to the inorganic solid electrolyte can be heated and melted by a heating device described below, and the cracks and gaps in the inorganic solid electrolyte can be repaired by the alkali metal-containing salt.

[0015] Inorganic solid electrolytes include, for example, lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-XThe inorganic solid electrolyte may be one or both of oxide solid electrolytes such as (PO4)3, Li-SiO-based glass, and Li-Al-SO-based glass; and sulfide solid electrolytes such as Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5-GeS2. In particular, inorganic solid electrolytes containing sulfides (sulfide solid electrolytes), especially inorganic solid electrolytes containing at least Li, S, and P as constituent elements, have high performance. The inorganic solid electrolyte may be amorphous or crystalline. The inorganic solid electrolyte may be any one that constitutes a granule together with an alkali metal-containing salt described later, and may be, for example, particulate. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

[0016] The alkali metal-containing salt is a salt containing at least an alkali metal ion as a cation. The type of the alkali metal ion is selected according to the type of carrier ion of the secondary battery, and may be a lithium ion, a sodium ion, a potassium ion, or a cesium ion. For example, when the secondary battery is a lithium ion battery, the alkali metal-containing salt is a Li-containing salt containing at least a lithium ion as a cation. The alkali metal-containing salt has a melting point and can melt when heated to the melting point or higher. The melting point of the alkali metal-containing salt can be appropriately selected in consideration of the heat resistance of the material constituting the secondary battery. If the melting point of the alkali metal-containing salt is too high, there is a risk of adversely affecting the material constituting the battery (for example, the seal part of the laminate film may deteriorate, etc.) when the alkali metal-containing salt is heated by the heating device 20 so that the temperature of the alkali metal-containing salt is at least the melting point. For example, the alkali metal-containing salt may have a melting point of 100° C. or less, 80° C. or less, or 60° C. or less. The lower limit of the melting point of the alkali metal-containing salt is not particularly limited. The alkali metal-containing salt may be a solid below its melting point when not heated by the heating device 20. For example, the melting point of the alkali metal-containing salt may be 20°C or higher, 25°C or higher, 30°C or higher, 35°C or higher, 40°C or higher, 45°C or higher, or 50°C or higher. The alkali metal-containing salt may be present in a particulate form in the granule before being heated by the heating device 20, may be present by coating the surface of the inorganic solid electrolyte, or may be present in other forms. The size of the alkali metal-containing salt is not particularly limited. The average particle diameter (D50) of the particles of the alkali metal-containing salt may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0017] The alkali metal-containing salt may have a first cation and a second cation, the first cation may be at least one selected from ammonium ion, phosphonium ion, pyridinium ion, and pyrrolidinium ion, and the second cation may be an alkali metal ion, preferably a lithium ion. The first cation may be a tetraalkylammonium ion, and the second cation may be an alkali metal ion, preferably a lithium ion. When the alkali metal-containing salt has the first cation, it tends to have a lower melting point than when it does not have the first cation.

[0018] Specific examples of the first cation include the following. Tetrahexylammonium ion, N(CH 13 )4 + Tetraoctylammonium ion, N(CH 17 )4 + Tetrabutylammonium ion, N(C4H9)4 + Tetraethylammonium ion, N(C2H5)4 + Tetraamylammonium ion, N(CH 11 )4 + Tetradecylammonium ion, N(C 10 H 21 )4 + Ethyl dimethyl phenylethyl ion, N(CH3)2(C2H5)(C2H5C6H5) + 1-Methyl-1-propylpiperidinium ion, (CH3)(C3H7)N(C5H 10 ) + Amyltriethylammonium ion, N(C2H5)3(C5H 11 ) + Methyltrioctylammonium ion, N(CH3)(C8H 17 )3 +

[0019] The molar ratio of the first cation and the second cation constituting the alkali metal-containing salt is not particularly limited. When the alkali metal-containing salt has both the first cation and the second cation, the melting point of the alkali metal-containing salt is lowered compared to when each of them is singly contained. From the viewpoint of greatly lowering the melting point of the alkali metal-containing salt and from the viewpoint of further increasing the alkali metal ion conductivity, the molar ratio of the second cation to the first cation (second cation / first cation) may be 0.05 or more and 19.0 or less. The molar ratio may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more, and may be 10.0 or less, 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, or 5.0 or less. Even if the molar ratio of the second cation to the first cation constituting the alkali metal-containing salt is high, such as 1.0 or more (e.g., the concentration of alkali metal ions in all cations is 50 mol % or more), the melting point of the alkali metal-containing salt may be sufficiently low, for example, 100°C or less, 80°C or less, or 60°C or less.

[0020] The cations constituting the alkali metal-containing salt may consist of only the first and second cations, or may contain other cations different from the first and second cations. Examples of other cations include ions containing poor metal elements. Examples of poor metal elements include Al and Ga. The total ratio of the first and second cations to the total cations constituting the alkali metal-containing salt may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 99 mol% or more, or 100 mol%.

[0021] The alkali metal-containing salt may have various anions. For example, the alkali metal-containing salt may have at least one anion selected from halogen ions, halide ions, hydrogen sulfate ions, sulfonyl amide ions, and complex ions containing H. Alternatively, the alkali metal-containing salt may have one or both of a first anion and a second anion, the first anion may be one or both of a halogen ion and a hydrogen sulfate ion, and the second anion may be a sulfonyl amide anion. According to the new findings of the present inventor, when the alkali metal-containing salt has the above anions, especially when it has one or both of a halogen ion and a hydrogen sulfate ion, and especially when it has a halogen ion, the melting point of the alkali metal-containing salt is likely to be specifically lowered. Also, according to the new findings of the present inventor, when the alkali metal-containing salt has a sulfonyl amide anion, the melting point of the alkali metal-containing salt is likely to be specifically lowered. Furthermore, according to the present inventors' new findings, when an alkali metal-containing salt has multiple types of anions, for example, when the alkali metal-containing salt has a first anion which is one or both of a halogen ion and a hydrogen sulfate ion, and a second anion which is a sulfonylamide anion, the melting point of the alkali metal-containing salt is also likely to be specifically decreased.

[0022] The halogen ions may be, for example, one or both of bromide and chloride ions.

[0023] The sulfonylamide anion is, for example, trifluoromethanesulfonylamide anion (TFSA anion, (CF3SO2)2N - ), Fluorosulfonylamide anion (FSA anion, (FSO2)2N - ), Fluorosulfonyl(trifluoromethanesulfonyl)amide anion (FTA anion, FSO2(CF3SO2)N -) and the like. The sulfonylamide anion may be one type only, or two or more types may be combined. Among the above sulfonylamide anions, the TFSA anion has low polarity and is particularly low in reactivity with other battery materials. In this regard, when the alkali metal-containing salt has the TFSA anion, the reaction between the alkali metal-containing salt and other battery materials is more easily suppressed.

[0024] The complex ion containing H may have, for example, an element M containing at least one of a nonmetal element and a metal element, and H bonded to the element M. In addition, the complex ion containing H may have the element M as a central element and H surrounding the element M bonded to each other via a covalent bond. In addition, the complex ion containing H may have (M m H n ) α- In this case, m is any positive number, and n and α can be any positive number depending on m and the valence of the element M. The element M may be a nonmetallic element or a metallic element capable of forming a complex ion. For example, the element M may contain at least one of B, C, and N as a nonmetallic element, or may contain B. Also, for example, the element M may contain at least one of Al, Ni, and Fe as a metallic element. In particular, when the complex ion contains B or contains C and B, higher ionic conductivity is likely to be ensured. Specific examples of complex ions containing H include (CB9H 10 ) - , (C.B. 11 H 12 ) - , (B 10 H 10 ) 2- , (B 12 H 12 ) 2- , (BH4) - , (NH2) - , (AlH4) - , and combinations thereof. In particular, (CB9H 10 ) - , (C.B. 11 H 12 ) -or a combination thereof, higher ionic conductivity is likely to be ensured.

[0025] When the alkali metal-containing salt has a first anion and a second anion, the molar ratio of the first anion to the second anion is not particularly limited. The molar ratio of the second anion to the first anion (second anion / first anion) may be more than 0 and 19.0 or less. The molar ratio may be 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, or 0.5 or more, and may be 10.0 or less, 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, or 5.0 or less.

[0026] The alkali metal-containing salt may contain anions other than the above-exemplified anions (at least one anion selected from halogen ions, halide ions, hydrogen sulfate ions, sulfonylamide ions, and complex ions containing H). The total ratio of the above-exemplified anions to all the anions constituting the alkali metal-containing salt may be 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 99 mol% or more, or 100 mol%.

[0027] An example of the composition and melting point of an alkali metal-containing salt discovered by the present inventors is shown below. (1) AmTEA·TFSA+Li·TFSA First cation: N(C2H5)3(C5H 11 ) + Second cation: Li + Anion: TFSA - Molar ratio of second cation to first cation: 1.0 Melting point: about 50℃ (2) MTOA·TFSA+Li·TFSA First cation: N(CH3)(C8H 17 )3 + Second cation: Li + Anion: TFSA - Molar ratio of second cation to first cation: 1.0 Melting point: about 50℃ (3)TAmA Br+Li TFSA First cation: N(CH 11 )4 + Second cation: Li + First anion: Br - Second anion: TFSA - Molar ratio of second cation to first cation: 1.0 Molar ratio of second anion to first anion: 1.0 Melting point: about 30℃ (4) TBA·TFSA+Li·TFSA First cation: N(C4H9)4 + Second cation: Li + Anion: TFSA - Molar ratio of second cation to first cation: 1.0 Melting point: about 60℃

[0028] Examples of the conductive assistant include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, aluminum, and stainless steel. The conductive assistant may be, for example, particulate or fibrous, and the size is not particularly limited. Only one type of conductive assistant may be used alone, or two or more types may be used in combination.

[0029] Examples of the binder include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. Only one type of binder may be used alone, or two or more types may be used in combination.

[0030] The positive electrode collector 11b may be any of those generally used as a positive electrode collector for a secondary battery. The positive electrode collector 11b may be in the form of a foil, a plate, a mesh, a punched metal, or a foam. The positive electrode collector 11b may be made of a metal foil or a metal mesh. In particular, a metal foil is excellent in terms of ease of handling. The positive electrode collector 11b may be made of a plurality of foils. Examples of metals constituting the positive electrode collector 11b include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, the positive electrode collector 11b may contain Al from the viewpoint of ensuring oxidation resistance. The positive electrode collector 11b may have some kind of coating layer on its surface for the purpose of adjusting resistance. The positive electrode collector 11b may be a metal foil or a substrate on which the above metal is plated or vapor-deposited. In addition, when the positive electrode current collector 11b is made of a plurality of metal foils, some layer may be present between the plurality of metal foils. The thickness of the positive electrode current collector is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0031] 1.1.2 Negative electrode 1, the negative electrode 12 may have a negative electrode active material layer 12a and a negative electrode current collector 12b in contact with the layer 12a. In this case, the negative electrode active material layer 12a may contain a predetermined active material and a predetermined granule.

[0032] The negative electrode active material layer 12a includes at least a negative electrode active material. The negative electrode active material layer 12a may include the above-mentioned granules. The negative electrode active material layer 12a may also include an electrolyte or an alkali metal-containing salt other than the above-mentioned granules. The negative electrode active material layer 12a may also include a conductive assistant and a binder. Furthermore, the negative electrode active material layer 12a may also include various additives. The content of each component in the negative electrode active material layer 12a may be appropriately determined according to the intended battery performance. For example, the content of the negative electrode active material may be 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, or 100 mass% or less, 95 mass% or less, or 90 mass% or less, based on the total solid content of the negative electrode active material layer 12a being 100 mass%. Alternatively, the negative electrode active material layer 12a may contain a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of the negative electrode active material, optionally granules, optionally solid electrolyte other than the granules, optionally alkali metal-containing salt other than the granules, optionally conductive assistant, and optionally binder, with the remainder being voids or other components. The shape of the negative electrode active material layer 12a is not particularly limited, and may be, for example, a sheet-like negative electrode active material layer having a substantially flat surface. The thickness of the negative electrode active material layer 12a is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0033] The negative electrode active material may be any material known as a negative electrode active material for secondary batteries. For example, when a lithium ion secondary battery is constructed, at least one selected from those containing Si (Si simple substance, Si alloy, Si compound), those containing carbon (graphite, hard carbon, etc.), those containing oxides (lithium titanate, etc.), and those containing Li (metallic lithium, lithium alloy, etc.) may be used as the negative electrode active material. The negative electrode active material may be one whose volume changes with charging and discharging, for example, one whose expansion rate is 5% or more (one whose volume changes by 5% or more when comparing before and after expansion). Among them, the negative electrode active material containing Si has a large volume change with charging and discharging the secondary battery 10. That is, when the negative electrode 12 contains an active material whose volume changes with charging and discharging, and a granule containing an inorganic solid electrolyte and an alkali metal-containing salt, and the active material contains Si, it is considered that the system 100 of the present disclosure has a more remarkable effect. The negative electrode active material may be used alone or in combination of two or more kinds. The negative electrode active material may be, for example, particulate, and the size is not particularly limited. The particles of the negative electrode active material may be solid particles, hollow particles, or particles having voids (porous particles). The particles of the negative electrode active material may be primary particles, or secondary particles formed by agglomeration of a plurality of primary particles. The average particle diameter (D50) of the particles of the negative electrode active material may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0034] The granules, inorganic solid electrolyte, alkali metal-containing salt, conductive assistant, binder, etc. that can be contained in the negative electrode active material layer 12a may be appropriately selected from, for example, those exemplified as those that can be contained in the positive electrode active material layer described above. The granules, inorganic solid electrolyte, alkali metal-containing salt, conductive assistant, binder, etc. that can be contained in the negative electrode active material layer 12a may be the same type as those that can be contained in the positive electrode active material layer 11a, or may be different types.

[0035] The negative electrode current collector 12b may be any of those generally used as negative electrode current collectors for secondary batteries. The negative electrode current collector 12b may be in the form of a foil, a plate, a mesh, a punched metal, or a foam. The negative electrode current collector 12b may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, a metal foil is excellent in terms of ease of handling. The negative electrode current collector 12b may be made of a plurality of foils or sheets. Examples of metals constituting the negative electrode current collector 12b include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, from the viewpoint of ensuring reduction resistance and being difficult to alloy with lithium, the negative electrode current collector 12b may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 12b may have some kind of coating layer on its surface for the purpose of adjusting resistance, etc. The negative electrode current collector 12b may be a metal foil or a substrate plated or vapor-deposited with the above metal. When the negative electrode current collector 12b is made of a plurality of metal foils, some layer may be present between the plurality of metal foils. The thickness of the negative electrode current collector 12b is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, or 1 mm or less or 100 μm or less.

[0036] 1.1.3 Electrolyte layer The electrolyte layer 13 is disposed between the positive electrode 11 and the negative electrode 12 and can function as a separator. The electrolyte layer 13 includes at least a solid electrolyte, and may further include a binder or the like. The electrolyte layer 13 may further include various additives. The content of each component in the electrolyte layer 13 is not particularly limited, and may be appropriately determined according to the intended battery performance. The shape of the electrolyte layer 13 is not particularly limited, and may be, for example, a sheet having a substantially flat surface. The thickness of the electrolyte layer 13 is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and may be 2 mm or less or 1 mm or less.

[0037] The solid electrolyte, binder, etc. contained in the electrolyte layer 13 may be appropriately selected from those exemplified as the electrolytes, binders, etc. that can be contained in the above-mentioned positive electrode active material layer 11a and negative electrode active material layer 12a.

[0038] 1.1.4 Other Configurations The secondary battery 10 may be one in which each of the above-mentioned components is housed inside an exterior body. Any known exterior body for a battery can be used as the exterior body. For example, an exterior body made of a laminate film can be used. The secondary battery 10 may be one having a plurality of positive electrodes 11, a plurality of negative electrodes 12, or a plurality of electrolyte layers 13. In addition, a plurality of secondary batteries 10 may be electrically connected and stacked in any manner to form an assembled battery. In this case, the assembled battery may be housed inside a known battery case. The secondary battery 10 may also have obvious components such as necessary terminals. The shape of the secondary battery 10 may be, for example, a coin type, a laminate type, a cylindrical type, a square type, or the like.

[0039] 1.2 Heating device As shown in Fig. 1, the secondary battery system 100 includes a heating device 20. The object to be heated by the heating device 20 includes the above-mentioned alkali metal-containing salt. In other words, the heating device 20 only needs to be configured to heat at least the alkali metal-containing salt. The heating device 20 may be configured to heat, for example, at least the positive electrode 11 of the secondary battery 10, or may be configured to heat at least the negative electrode 12, or may be configured to heat the positive electrode 11, the negative electrode 12, and the electrolyte layer 13 of the secondary battery 10 as a whole.

[0040] The heating method of the heating device 20 is not particularly limited as long as it can heat the alkali metal-containing salt to a temperature equal to or higher than its melting point. For example, various methods such as resistance heating, induction heating, dielectric heating, microwave heating, and hot air heating can be adopted. The heating device 20 may be configured to be switchable between a mode in which the alkali metal-containing salt is heated to a temperature equal to or higher than its melting point, and a mode in which the alkali metal-containing salt is heated or not heated to a temperature lower than its melting point.

[0041] The position where the heating device 20 is installed and the number of the heating devices 20 are not particularly limited. Although FIG. 1 shows a form in which the heating device 20 is arranged on each of the positive electrode 11 side and the negative electrode 12 side, the position and the number of the heating devices 20 are not limited thereto. The heating device 20 may be arranged, for example, inside or outside the exterior body of the secondary battery 10. In addition, the heating device 20 may be configured to heat one secondary battery 10 or to heat multiple secondary batteries 10.

[0042] The maximum heating temperature by the heating device 20 may be equal to or higher than the melting point of the alkali metal-containing salt. On the other hand, from the viewpoint of suppressing material deterioration of the secondary battery 10, the heating temperature by the heating device 20 may be 100° C. or lower, 90° C. or lower, 80° C. or lower, 70° C. or lower, or 60° C. or lower.

[0043] 1.3 Other configurations 1.3.1 Control Unit 1, the secondary battery system 100 may include a control device 30. The control device 30 controls heating by the heating device 20. The control device 30 may include a CPU, a RAM, a ROM, and the like.

[0044] As described above, one or both of the positive electrode 11 and the negative electrode 12 of the secondary battery 10 contain an active material whose volume changes with charging and discharging, together with granules containing an inorganic solid electrolyte. Therefore, when the secondary battery 10 is repeatedly charged and discharged, cracks and gaps are likely to occur in the inorganic solid electrolyte due to the volume change of the active material. Such cracks and gaps cause breaks in the ion conduction path and the conductive path in the electrode, and the performance of the secondary battery 10 may decrease below a certain level. For example, the resistance of the secondary battery 10 increases.

[0045] The control device 30 may control the heating by the heating device 20 so that the temperature of the alkali metal-containing salt is equal to or higher than its melting point when it is determined that the performance of the secondary battery 10 is equal to or lower than a certain level. The heating time by the heating device 20 is not particularly limited, and may be, for example, the time until the alkali metal-containing salt in the electrode is sufficiently liquefied. For example, the control device 30 may control the ON / OFF switching of the heating device 20 so that heating by the heating device 20 is started when it is determined that the performance of the secondary battery 10 is equal to or lower than a certain level. Alternatively, the control device 30 may control the heating of the heating device 20 so that the amount of heat by the heating device 20 is increased when it is determined that the performance of the secondary battery 10 is equal to or lower than a certain level. In this way, by controlling the heating by the heating device 20 with the control device 30 to heat the alkali metal-containing salt to a temperature equal to or higher than its melting point, the cracks and gaps generated in the positive electrode 11 and the negative electrode 12 can be filled with the liquid alkali metal-containing salt. That is, the cracks and gaps generated in the positive electrode 11 and the negative electrode 12 are eliminated by the alkali metal-containing salt. The alkali metal-containing salt contains alkali metal ions and therefore has a certain degree of alkali metal ion conductivity or electrical conductivity. Therefore, the ion conduction path or electrical conduction path that is interrupted by a crack or gap is reconnected via the alkali metal-containing salt. As a result, the performance of the secondary battery 10 is restored.

[0046] Whether the performance of the secondary battery 10 is below a certain level can be determined based on various criteria. For example, when an ion conduction path or a conductive path in the electrode is interrupted, (1) the voltage value of the secondary battery at a predetermined SOC decreases, (2) the resistance of the secondary battery increases, or (3) the output of the secondary battery decreases, compared to when the ion conduction path or the conductive path in the electrode is not interrupted. That is, whether the performance of the secondary battery is below a certain level can be determined based on the voltage, resistance, output, or the like of the secondary battery. For example, as shown in FIG. 1, the secondary battery system 100 may have a voltage measurement device as the measurement device 40, and the voltage measurement device may measure the voltage of the secondary battery 10, and the performance of the secondary battery 10 may be based on the voltage. Specifically, the voltage measurement device measures the voltage of the secondary battery 10 at a predetermined SOC, and when the voltage value measured by the voltage measurement device is below a certain level, it may be determined that the performance of the secondary battery 10 is below a certain level, and the control device 30 may perform the above-mentioned control. 1, the secondary battery system 100 may have a resistance measuring device as the measuring device 40, and the resistance measuring device may measure the resistance of the secondary battery 10, and the performance of the secondary battery 10 may be based on the resistance. Specifically, the resistance of the secondary battery 10 may be measured by the resistance measuring device, and when the resistance value measured by the resistance measuring device is equal to or greater than a certain level, it may be determined that the performance of the secondary battery 10 is equal to or less than a certain level, and the above-mentioned control may be performed by the control device 30.

[0047] The determination of whether the performance of the secondary battery is below a certain level may be performed, for example, by the control device 30 or by a device other than the control device 30. The threshold value for whether the performance of the secondary battery 10 is below a certain level is not particularly limited. An appropriate threshold value may be set depending on the performance required of the secondary battery 10, etc.

[0048] The control device 30 may control the heating by the heating device 20 so that the temperature of the alkali metal-containing salt is below its melting point when it is determined that the performance of the secondary battery 10 exceeds a certain level. For example, the control device 30 may control the ON / OFF switching of the heating device 20 so that the heating by the heating device 20 is stopped when it is determined that the performance of the secondary battery 10 exceeds a certain level. Alternatively, the control device 30 may control the heating by the heating device 20 so that the amount of heating by the heating device 20 is reduced when it is determined that the performance of the secondary battery 10 exceeds a certain level.

[0049] 1.3.2 Measuring Equipment When the secondary battery system 100 includes a voltage measuring device as the measuring device 40, the voltage measuring device may be one that is capable of measuring the voltage of the secondary battery 10. The voltage measuring device may be one that monitors the voltages of a plurality of secondary batteries 10. When the secondary battery system 100 includes a resistance measuring device as the measuring device 40, the resistance measuring device may be one that is capable of measuring the resistance of the secondary battery 10. The resistance measuring device may be one that monitors the resistance of a plurality of secondary batteries 10. Specific configurations of the voltage measuring device and the resistance measuring device are known. The measuring device 40 may be one that serves as both a voltage measuring device and a resistance measuring device.

[0050] 1.4 Examples of control flow FIG. 3 shows a specific example of a control flow in the secondary battery system 100. FIG. 3 shows a control flow in the case where it is determined whether the performance of the secondary battery 10 is equal to or lower than a certain level, based on the voltage of the secondary battery 10. As described above, the voltage of the secondary battery 10 at a specified SOC gradually decreases due to the interruption of the ion conduction path or the conductive path in the electrodes. The control flow shown in FIG. 3 sets a threshold value for the voltage value of the secondary battery 10, and when the voltage value falls below the threshold value, the heating device 20, the circulation fan, etc. are turned on to heat the secondary battery 10, and the alkali metal-containing salt contained in the electrodes of the secondary battery 10 is heated to a melting point or higher to melt it, thereby repairing the solid-solid interface in the electrodes.

[0051] 3, first, the voltage value of the secondary battery 10 at a predetermined SOC is obtained. The voltage value of the secondary battery 10 can be obtained by a voltage measuring device 40, for example.

[0052] If the voltage value of the secondary battery 10 is above the threshold value, it is determined that the performance of the secondary battery 10 exceeds a certain level, and heating control by the heating device 20 is not performed, and for example, the heating device 20 is kept OFF and the control flow is terminated. On the other hand, if the voltage value is below the threshold value, it is determined that the performance of the secondary battery 10 is below a certain level, and the heating device 20 is turned ON, the circulation fan is turned ON, heating of the alkali metal-containing salt by the heating device 20 is started, and the alkali metal-containing salt is liquefied.

[0053] After a certain time has elapsed, the heating device 20 and the circulation fan are turned OFF, and the voltage value of the secondary battery 10 at the specified SOC is acquired again. If the voltage value is still below the threshold, the heating device 20 and the circulation fan are turned ON again to heat and liquefy the alkali metal-containing salt. On the other hand, if the voltage value is above the threshold, it is determined that the performance of the secondary battery 10 exceeds a certain level, and the heating device 20 is not used again for heating, and the control flow is ended, for example, with the heating device 20 kept OFF.

[0054] The control flow for determining whether the performance of the secondary battery 10 is equal to or lower than a certain level based on the resistance of the secondary battery 10 may be the same as that of Fig. 3. That is, a threshold value is set for the resistance value of the secondary battery 10, and when the resistance value exceeds the threshold value, the heating device 20, the circulation fan, etc. are turned on to heat the secondary battery 10, and the alkali metal-containing salt contained in the electrodes of the secondary battery 10 is heated to a melting point or higher to melt it, thereby repairing the solid-solid interface in the electrodes.

[0055] Specifically, first, the resistance value of the secondary battery 10 is obtained. The resistance value of the secondary battery 10 can be obtained by, for example, a resistance measuring device 40.

[0056] If the resistance value of the secondary battery 10 is below the threshold, it is determined that the performance of the secondary battery 10 exceeds a certain level, and heating control by the heating device 20 is not performed, and for example, the heating device 20 is kept OFF and the control flow is terminated. On the other hand, if the resistance value is above the threshold, it is determined that the performance of the secondary battery 10 is below a certain level, and the heating device 20 is turned ON, the circulation fan is turned ON, heating of the alkali metal-containing salt by the heating device 20 is started, and the alkali metal-containing salt is liquefied.

[0057] After a certain time has elapsed, the heating device 20 and the circulation fan are turned OFF, and the resistance value of the secondary battery 10 is acquired again. If the resistance value is still above the threshold, the heating device 20 and the circulation fan are turned ON again to heat and liquefy the alkali metal-containing salt. On the other hand, if the resistance value is below the threshold, it is determined that the performance of the secondary battery 10 exceeds a certain level, and the heating device 20 is not heated again, and the control flow is ended, for example, with the heating device 20 kept OFF.

[0058] 2. Method for restoring secondary battery performance As described above, the secondary battery system 100 can eliminate interruptions in the ion conduction paths and the conductive paths in the positive electrode 11 and the negative electrode 12 of the secondary battery 10, thereby recovering the performance of the secondary battery 10. In this respect, the technology of the present disclosure also has an aspect as a method for recovering the performance of a secondary battery. That is, the method for recovering the performance of a secondary battery of the present disclosure includes the following steps: Determining whether the performance of the secondary battery is below a certain level; and performing a process for recovering the performance of the secondary battery when it is determined that the performance of the secondary battery is equal to or lower than a certain level; The secondary battery has a positive electrode and a negative electrode, One or both of the positive electrode and the negative electrode includes an active material and a granule, the active material includes a material whose volume changes with charging and discharging of the secondary battery, The granules contain an inorganic solid electrolyte and an alkali metal-containing salt, The process for recovering the performance of the secondary battery includes heating the alkali metal-containing salt contained in one or both of the positive electrode and the negative electrode of the secondary battery to a temperature equal to or higher than the melting point of the alkali metal-containing salt.

[0059] Details of the criteria for determining whether the performance of the secondary battery is below a certain level and details of the heating control for recovering the performance of the secondary battery are as described in the secondary battery system.

[0060] As described above, the technology disclosed herein can eliminate the interruption of the ion conduction path or the conductive path in the positive electrode or the negative electrode, thereby recovering the performance of the secondary battery. In addition, the technology disclosed herein can be expected to have the effect of suppressing or repairing the cracking of the electrolyte layer and the dendrite short circuit in the negative electrode.

[0061] 3. Manufacturing method of secondary battery The technology of the present disclosure also has an aspect of a method for manufacturing a secondary battery, which includes obtaining granules containing an inorganic solid electrolyte and an alkali metal-containing salt, mixing the granules with an active material to obtain an electrode mixture, and forming one of a positive electrode and a negative electrode using the electrode mixture.

[0062] The granules can be obtained, for example, by mixing the inorganic solid electrolyte and the alkali metal-containing salt described above. The mixing may be performed according to a known mixing method. For example, the inorganic solid electrolyte and the alkali metal-containing salt may be mixed using a mechanical mixing means or may be mixed manually using a mortar or the like. There are no particular limitations on the mixing temperature, mixing time, or mixing atmosphere, and any temperature, time, or atmosphere may be used as long as the inorganic solid electrolyte and the alkali metal-containing salt can be appropriately granulated. In particular, by heating the inorganic solid electrolyte and the alkali metal-containing salt when mixing them, the inorganic solid electrolyte and the alkali metal-containing salt can be easily granulated appropriately. For example, when mixing the inorganic solid electrolyte and the alkali metal-containing salt, the inorganic solid electrolyte and the alkali metal-containing salt may be heated to a temperature equal to or higher than the melting point of the alkali metal-containing salt.

[0063] The electrode mixture can be obtained by mixing the above-mentioned granules and active material. The electrode mixture may be obtained by mixing an electrolyte other than the granules, an alkali metal-containing salt other than the granules, a conductive assistant, a binder, etc., in addition to the granules and the active material. As described above, the active material contains a substance whose volume changes with the charge and discharge of the secondary battery. The conductive assistant and the binder are also as described above. The mixing may be performed according to a known mixing method. The inorganic solid electrolyte and the alkali metal-containing salt may be mixed, for example, using a mechanical mixing means, or may be mixed manually using a mortar or the like. There are no particular limitations on the mixing temperature, mixing time, or mixing atmosphere, and the temperature, time, and atmosphere may be suitable for obtaining the electrode mixture. The electrode mixture may be in the form of a slurry or paste. That is, the electrode mixture may be obtained by mixing a granule, an active material, optionally an electrolyte other than the granule, optionally an alkali metal-containing salt other than the granule, optionally a conductive assistant, optionally a binder, and a dispersion medium (e.g., an organic solvent).

[0064] The electrode mixture can be used to form one of a positive electrode and a negative electrode. For example, a slurry containing the electrode mixture is applied to the surface of a current collector and then dried to obtain an electrode having a current collector and an active material layer. The electrode can be either a positive electrode or a negative electrode depending on the type of active material contained in the electrode mixture. A secondary battery can be constructed using the electrode thus obtained together with the above-mentioned electrolyte layer and the like. The secondary battery and a heating device can also constitute the above-mentioned secondary electron system.

[0065] As described above, the method for producing a secondary battery according to the present disclosure is characterized in that the inorganic solid electrolyte and the alkali metal-containing salt are granulated in advance before obtaining an electrode mixture, and other steps may be the same as those known in the art. By granulating the inorganic solid electrolyte and the alkali metal-containing salt in advance, the alkali metal-containing salt is disposed in the vicinity of the inorganic solid electrolyte in the electrode of the secondary battery. As a result, even if, for example, a volume change occurs in the active material due to charging and discharging the secondary battery, and cracks or gaps occur in the inorganic solid electrolyte due to the volume change, the alkali metal-containing salt in the vicinity of the inorganic solid electrolyte is heated and melted by the above-mentioned heating device, so that the cracks or gaps occurring in the inorganic solid electrolyte can be repaired by the alkali metal-containing salt. EXAMPLES

[0066] The technology of the present disclosure will be described in more detail below with reference to examples, but the technology of the present disclosure is not limited to the following examples.

[0067] 1. Preparation of Positive Electrode A positive electrode slurry was prepared by stirring a positive electrode mixture containing an NCA-based positive electrode active material, a sulfide-based solid electrolyte, vapor-grown carbon fiber, a PVdF-based binder, and butyl butyrate with an ultrasonic dispersing device. Here, the mass ratio of the NCA-based positive electrode active material: the sulfide-based solid electrolyte: the vapor-grown carbon fiber: the PVdF-based binder was 100:16:2:0.75. The positive electrode slurry was applied onto an Al foil as a positive electrode current collector by a blade method, and dried on a hot plate at 100°C for 30 minutes to obtain a positive electrode having a positive electrode active material layer and a positive electrode current collector foil.

[0068] 2. Preparation of Li-containing salt A Li-containing salt was prepared by heating and mixing tetrabutylammonium bis(trifluoromethanesulfonyl)amide (TBA·TFSA) and lithium bis(trifluoromethanesulfonyl)amide (Li·TFSA) in a molar ratio of 1:1. The melting point of the obtained Li-containing salt was 56°C.

[0069] 3. Preparation of the Negative Electrode 3.1 Comparative Example 1 After mixing the vapor-grown carbon fiber, the BR-based binder, and mesitylene with a homogenizer, the sulfide-based solid electrolyte and the Li-containing salt were added and mixed with the homogenizer, and finally, powdered Si was added and stirred with the homogenizer to prepare a negative electrode slurry. Here, the mass ratio of powdered Si:sulfide-based solid electrolyte:Li-containing salt:vapor-grown carbon fiber:BR-based binder was 100:54:11.5:8:2. The negative electrode slurry was applied to a Cu foil as a negative electrode current collector foil by a blade method, and dried on a hot plate at 100°C for 30 minutes to obtain a negative electrode having a negative electrode active material layer and a negative electrode current collector foil.

[0070] 3.2 Comparative Example 2 Powdered Si and Li-containing salt were mixed in a mortar at the same mass ratio as in Comparative Example 1 while heating to 60° C. to obtain a granule of Si and Li-containing salt. The granule was added and stirred at the same timing as powdered Si in Comparative Example 1 to obtain a negative electrode slurry. The negative electrode slurry was applied and dried in the same manner as in Comparative Example 1 to obtain a negative electrode having a negative electrode active material layer and a negative electrode current collector foil.

[0071] 3.3 Example 1 The sulfide-based solid electrolyte and the Li-containing salt were mixed in a mortar at the same mass ratio as in Comparative Example 1 while heating to 60° C. to obtain a granule of the sulfide-based solid electrolyte and the Li-containing salt. The granule was added and stirred at the same time as the sulfide-based solid electrolyte in Comparative Example 1 to obtain a negative electrode slurry. The negative electrode slurry was applied and dried in the same manner as in Comparative Example 1 to obtain a negative electrode having a negative electrode active material layer and a negative electrode current collector foil.

[0072] 3.4 Example 2 After dissolving the Li-containing salt in butyl butyrate, the sulfide-based electrolyte was added in the same mass ratio as in Comparative Example 1, mixed in a mortar, and dried at 100°C to obtain a granule of the sulfide-based solid electrolyte and the Li-containing salt. The granule was added and stirred at the same time as the sulfide-based solid electrolyte in Comparative Example 1 to obtain a negative electrode slurry. The negative electrode slurry was applied and dried in the same manner as in Comparative Example 1 to obtain a negative electrode having a negative electrode active material layer and a negative electrode current collector foil.

[0073] 4. Preparation of Electrolyte Layer An electrolyte mixture containing a sulfide-based solid electrolyte, a PVdF-based binder, and butyl butyrate was stirred by an ultrasonic dispersing device to prepare an electrolyte slurry. Here, the mass ratio of the sulfide-based solid electrolyte to the PVdF-based binder was 99.6:0.4. The electrolyte slurry was applied onto an Al foil substrate by a blade method, and dried on a hot plate at 100°C for 30 minutes to form a solid electrolyte layer on the surface of the Al foil.

[0074] 5. Preparation of the first laminate The positive electrode and the solid electrolyte layer were laminated so as to overlap each other, and pressed with a roll press at a pressure of 50 kN / cm and a temperature of 160°C. The Al foil was then peeled off from the solid electrolyte layer and a 1 cm 2 A first laminate was obtained by punching out the resulting sheet into pieces of the same size.

[0075] 6. Preparation of the second laminate The negative electrode and the solid electrolyte layer were laminated so as to overlap each other, and then pressed with a roll press at a pressure of 30 kN / cm at room temperature. The Al foil was then peeled off from the solid electrolyte layer to obtain a second laminate.

[0076] 7. Preparation of the third laminate An additional solid electrolyte layer was laminated so as to overlap the solid electrolyte layer of the second laminate, and then pre-pressed with a flat uniaxial press at a pressure of 100 MPa and a temperature of 25°C. The Al foil was then peeled off from the additional solid electrolyte layer, and the laminate was cut to a thickness of 1.08 cm. 2 A third laminate having an additional solid electrolyte layer was obtained by punching out the resulting laminate to a size of 10 mm.

[0077] 8. Fabrication of Battery Stacks The first and third stacks were stacked so that the solid electrolyte layers overlapped each other, and then pressed in a flat uniaxial press at a pressure of 400 MPa and a temperature of 135°C to obtain a battery stack having a positive electrode, a solid electrolyte layer, and a negative electrode in this order.

[0078] 9. Battery stack restraint The battery stack obtained as described above was sandwiched between two restraint plates, and these two restraint plates were fastened with a fastener at a restraint pressure of 2 MPa to fix the distance between these two restraint plates.

[0079] 10.Charging and discharging The restrained battery stack was charged and discharged three times under the following conditions. Charging: After constant current charging at 1 / 10C up to 3.7V, constant voltage charging was performed at 3.7V up to a final current of 1 / 100C. Discharge: After constant current discharge at 1 / 10C up to 2.7V, constant voltage discharge was performed at 2.7V up to a final current of 1 / 100C.

[0080] 11. Heating and resistance measurement For the battery stack after charging and discharging, resistance measurements were performed before and after heating under the following conditions, and the resistance increase rate was calculated as [(resistance value after heating) / (resistance value before heating)]×100. Resistance measurement before heating: The restrained battery stack was left in a 25°C thermostatic chamber for 4 hours. After that, it was charged at a constant current up to 3.14V, and then charged at a constant voltage up to a cut-off current of 1 / 100C. After that, it was discharged at 3C for 10 seconds. The voltage drop after 10 seconds was divided by the current to calculate the resistance before heating. Resistance measurement after heating: The restrained battery stack was heated by leaving it in a thermostatic chamber at 60° C. for 4 hours. The resistance value after heating was then calculated using the same method as for measuring the resistance before heating.

[0081] 12.Results Table 1 below shows the results of the resistance increase rate of the battery stack for each of Comparative Examples 1 and 2 and Examples 1 and 2.

[0082] [Table 1]

[0083] From the results shown in Table 1, it can be said that with a secondary battery system having the following configurations (1) to (3), even if cracks or gaps occur in the solid electrolyte due to volume changes in the active material accompanying charging and discharging of the secondary battery, causing a decrease in the performance of the secondary battery (for example, an increase in the resistance of the secondary battery), the performance of the secondary battery can be restored by heating.

[0084] (1) The secondary battery system includes a secondary battery and a heating device. (2) The secondary battery has a positive electrode and a negative electrode, one or both of the positive electrode and the negative electrode contain an active material and a granule, the active material contains a substance whose volume changes with charging and discharging of the secondary battery, and the granule contains an inorganic solid electrolyte and an alkali metal-containing salt. (3) The object to be heated by the heating device contains the alkali metal-containing salt.

[0085] In the above embodiment, powdered Si is used as an active material whose volume changes with charging and discharging of the secondary battery, but the technology of the present disclosure is not limited to this. An active material other than Si may be used as an active material whose volume changes with charging and discharging of the secondary battery. A positive electrode active material may be used as an active material whose volume changes with charging and discharging of the secondary battery.

[0086] In the above embodiment, a sulfide-based solid electrolyte is used as the inorganic solid electrolyte, and a Li-containing salt is used as the alkali metal-containing salt, but the technology of the present disclosure is not limited to this. A solid electrolyte other than a sulfide may be used as the inorganic solid electrolyte, and an alkali metal-containing salt other than a Li-containing salt may be used depending on the type of carrier ion of the secondary battery.

[0087] In the above embodiment, a granule of an inorganic solid electrolyte and an alkali metal-containing salt is used as the material for constituting the negative electrode composite material, but the technology of the present disclosure is not limited to this. A granule of an inorganic solid electrolyte and an alkali metal-containing salt may be used as the material for constituting the positive electrode composite material.

[0088] In the above embodiment, the secondary battery is an all-solid-state battery that does not contain a liquid component at room temperature, but the form of the secondary battery is not limited to this. The secondary battery may partially contain a liquid component. [Explanation of symbols]

[0089] 10 Secondary battery 11 Positive electrode 12 Negative electrode 13 Electrolyte layer 20 Heating device 30 Control device 40 Measuring devices (voltage measuring devices and / or resistance measuring devices) 100 Secondary battery system

Claims

1. A secondary battery system comprising a secondary battery, a heating device, and a control device, The secondary battery has a positive electrode and a negative electrode, One or both of the positive electrode and the negative electrode includes an active material and a granule, the active material includes a material whose volume changes with charging and discharging of the secondary battery, The granules contain an inorganic solid electrolyte and an alkali metal-containing salt, The object to be heated by the heating device includes the alkali metal-containing salt, when it is determined that the performance of the secondary battery is equal to or lower than a certain level, the control device controls the heating by the heating device so that the temperature of the alkali metal-containing salt is equal to or higher than a melting point of the alkali metal-containing salt. Secondary battery system.

2. when it is determined that the performance of the secondary battery exceeds a certain level, the control device controls the heating by the heating device so that the temperature of the alkali metal-containing salt is lower than the melting point of the alkali metal-containing salt. The secondary battery system according to claim 1 .

3. A voltage measuring device is provided. The voltage measuring device measures a voltage of the secondary battery, The performance of the secondary battery is based on the voltage. The secondary battery system according to claim 1 .

4. A resistance measuring device is provided. The resistance measuring device measures the resistance of the secondary battery, The performance of the secondary battery is based on the resistance. The secondary battery system according to claim 1 .

5. The alkali metal-containing salt has a melting point of 100° C. or less. The secondary battery system according to any one of claims 1 to 4.

6. The positive electrode includes the active material and the granules, The active material contains S. The secondary battery system according to any one of claims 1 to 4.

7. The negative electrode includes the active material and the granules, The active material contains Si. The secondary battery system according to any one of claims 1 to 4.

8. The inorganic solid electrolyte contains a sulfide. The secondary battery system according to any one of claims 1 to 4.

9. the alkali metal-containing salt has a first cation and a second cation; the first cation is at least one selected from an ammonium ion, a phosphonium ion, a pyridinium ion, and a pyrrolidinium ion; The second cation is an alkali metal ion. The secondary battery system according to any one of claims 1 to 4.

10. the alkali metal-containing salt has a first cation and a second cation; the first cation is a tetraalkylammonium ion; The second cation is an alkali metal ion. The secondary battery system according to any one of claims 1 to 4.

11. The alkali metal-containing salt has at least one anion selected from a halogen ion, a halide ion, a hydrogen sulfate ion, a sulfonyl amide ion, and a complex ion containing H. The secondary battery system according to claim 9 .

12. the alkali metal-containing salt has one or both of a first anion and a second anion; the first anion is one or both of a halide ion and a hydrogen sulfate ion; The second anion is a sulfonylamide anion. The secondary battery system according to claim 11 .

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