Secondary battery and manufacturing method for the same

Abstract

(Project) Improve the Coulomb efficiency of a secondary battery equipped with a metal lithium negative electrode. (Solution) The secondary battery of the present disclosure comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, wherein the negative electrode active material layer comprises a first material and a second material, wherein the first material is at least one of an alloy of Li and element X and a compound of Li and element X, and the second material is at least one of a single metal element M, an alloy of Li and metal element M, and a compound of Li and metal element M, and furthermore, the generation energy ELiX of the first material is lower than the generation energy EMX of the compound of metal element M and element X.

Description

Technology Field

[0001] The present invention discloses a secondary battery and a method for manufacturing the same. Background Technology

[0002] Patent Document 1 discloses an all-solid-state battery comprising a positive electrode, a solid electrolyte layer, a negative electrode current collector, and a Li-Mg alloy that precipitates between the solid electrolyte layer and the negative electrode current collector upon charging. Patent Document 2 discloses a negative electrode material used in a metal secondary battery comprising MgH2 and a metal catalyst that contacts the MgH2 and improves the reversibility of a conversion reaction. Patent Document 3 discloses an all-solid-state lithium secondary battery comprising a positive electrode, a solid electrolyte layer, a negative electrode, and a predetermined metal layer formed between the solid electrolyte layer and the negative electrode. Patent Document 4 discloses a negative electrode for an all-solid-state secondary battery comprising a negative electrode current collector and a coating layer that covers the negative electrode current collector and allows metallic lithium to precipitate through a lithium alloy layer upon charging. Prior art literature

[0003] Japanese Published Patent Application No. 2020-184513, Japanese Published Patent Application No. 2012-038697, International Publication No. 2013 / 131241, Japanese Published Patent Application No. 2018-129159 The problem to be solved

[0004] A secondary battery equipped with a metal lithium negative electrode has room for improvement in terms of Coulomb efficiency. means of solving the problem

[0005] The present invention discloses the following multiple embodiments as a means to solve the above problem.

[0006] <Mode 1>

[0007] As a secondary battery, it comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and

[0008] The above negative electrode active material layer comprises a first material and a second material, and

[0009] The first material is at least one of an alloy of Li and element X, and a compound of Li and element X, and

[0010] The second material is at least one of the following: a single element of metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M, and also

[0011] The generation energy E of the first substance above LiX a, formation energy E of the compound of the metal element M and the element X MX Lower, secondary battery.

[0012] <Mode 2>

[0013] The above negative electrode active material layer comprises the above first material formed as a film, and

[0014] A secondary battery of Embodiment 1, wherein the thickness of the first material formed as a film is 10 nm or more and 50 μm or less.

[0015] <Mode 3>

[0016] As a secondary battery, it comprises a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and metallic lithium that is precipitated between the solid electrolyte layer and the negative electrode current collector by charging.

[0017] Between the solid electrolyte layer and the negative electrode current collector, a compound of metal element M and element X exists, and also

[0018] The formation energy E of the compound of the above metal element M and the above element X MX a. Formation energy E of the compound of Li and the above element X LiX Higher, secondary battery.

[0019] <Mode 4>

[0020] A secondary battery of Embodiment 3, configured such that when charging, a compound of the metal element M and the element X decomposes to form a compound of the Li and the element X on the surface of the negative electrode current collector.

[0021] <Mode 5>

[0022] A secondary battery of any one of embodiments 1 to 4, wherein the above metal element M and the above element X satisfy the following relationships (1) and (2):

[0023] (1) Energy E of the formation of the compound of the metal element M and the element X MX a, Formation energy E of the compound of Li and the metal element M LiM Lower, and also

[0024] (2) Formation energy E of the compound of Li and the element X LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than.

[0025] <Mode 6>

[0026] A secondary battery of any one of embodiments 1 to 5, wherein the metal element M is Mg.

[0027] <Mode 7>

[0028] A secondary battery of Embodiment 6, wherein the above element X is at least one of Bi, Sb, In, Sn, H, I, Ga, Te, Hg, Cd, Si, B, As, Zn, Ge, Br, P, and Se.

[0029] <Mode 8>

[0030] A secondary battery of any one of embodiments 1 to 7, wherein the above-mentioned element X is at least one of H, B, and P.

[0031] <Mode 9>

[0032] The above generated energy E MX and the above generation energy E LiXA secondary battery of any one of embodiments 1 to 8, wherein the difference is 0.027 eV / atom or greater.

[0033] <Mode 10>

[0034] As a method for manufacturing a secondary battery,

[0035] Obtaining a laminate having a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and a compound of metal element M and element X disposed between the solid electrolyte layer and the negative electrode current collector, and,

[0036] The method comprises charging the laminate to supply lithium ions between the solid electrolyte layer and the negative electrode current collector, and causing a conversion reaction of a compound of the metal element M and the element X to produce a first material and a second material.

[0037] The first material is at least one of an alloy of Li and element X, and a compound of Li and element X, and

[0038] A method for manufacturing the second material, wherein the second material is at least one of a unit of metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M. Effects of the invention

[0039] The secondary battery of the present disclosure has a metal lithium negative electrode and also has excellent Coulomb efficiency. Brief explanation of the drawing

[0040] Figure 1 schematically shows the configuration of a secondary battery (101). Figure 2 schematically shows the configuration of a secondary battery (102). FIG. 3 schematically illustrates the change in configuration of a secondary battery (101, 102) accompanying charging and discharging. FIG. 4 schematically illustrates the process from stacking each layer to charging as a method for manufacturing a secondary battery (101, 102). Figure 5 schematically shows the configuration of the evaluation cell. Figure 6 is a graph comparing the Coulomb efficiency of the evaluation cell. Figure 7 shows the structure and Mg distribution before and after charging, respectively, for the cross-section of the evaluation cell of Comparative Example 3. FIG. 8 shows the structure and Mg distribution before and after charging, respectively, for the cross-section of the evaluation cell of Example 3. Figure 9 shows the respective distributions of S, Mg, and Ni after filling for the cross-section of the evaluation cell of Example 3. Figure 10 shows the CV measurement results of the evaluation cell of Example 3. Figure 11 shows the XRD measurement results at a specific point of the evaluation cell of Example 3. Figure 12 shows the respective distributions of S, Mg, and Ni after filling for the cross-section of the evaluation cell of Example 4. Specific details for implementing the invention

[0041] Hereinafter, a secondary battery and a method for manufacturing the same related to an embodiment will be described with reference to the drawings, but the technology of the present disclosure is not limited to the following embodiments.

[0042] 1. Secondary battery (Type 1)

[0043] FIG. 1 schematically illustrates the configuration of a secondary battery (101) related to a first form. As shown in FIG. 1, the secondary battery (101) comprises a positive electrode active material layer (10), a solid electrolyte layer (20), and a negative electrode active material layer (30). The negative electrode active material layer (30) comprises a first material (31) and a second material (32). The first material (31) is at least one of an alloy of Li and element X, and a compound of Li and said element X. The second material (32) is at least one of a single metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M. The generation energy E of the first material (31) LiX is the formation energy E of the compound of the metal element M and the element X. MX Lower than.

[0044] 1.1 Positive electrode active material layer

[0045] The positive electrode active material layer (10) may include a positive electrode active material and, optionally, may also include an electrolyte, a conductivity aid, a binder, etc. Additionally, the positive electrode active material layer (10) may include various additives. The respective contents of the positive electrode active material, electrolyte, conductivity aid, and binder in the positive electrode active material layer (10) may be appropriately determined according to the intended battery performance. For example, with the entire positive electrode active material layer (10) (total solid content) set to 100 mass%, the content of the positive electrode active material may be 40 mass% or more, 50 mass% or more, or 60 mass% or more, or 100 mass% or less, or 90 mass% or less. The shape of the positive electrode active material layer (10) is not particularly limited and, for example, may be a sheet having a roughly flat shape. The thickness of the positive electrode active material layer (10) is not particularly limited, for example, it may be 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or more, or 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0046] 1.1.1 Positive electrode active material

[0047] The positive electrode active material is a known positive electrode active material for secondary batteries, and it is sufficient if it is capable of releasing Li ions during charging and absorbing Li ions during discharging. For example, lithium cobaltate, lithium nickelate, and LiNi may be used as positive electrode active materials. 1 / 3 Co 1 / 3 Mn 1 / 3Various lithium-containing oxides such as O2, lithium manganate, and spinel-based lithium compounds may be used. Alternatively, as a positive electrode active material, one-element sulfur or sulfur in which lithium is adsorbed may be used. In particular, when the positive electrode active material layer (10) contains a lithium-containing oxide as a positive electrode active material, Li ions can be supplied appropriately from the positive electrode active material to the negative electrode side during charging, and the expansion and contraction of the positive electrode active material during charging and discharging is small, making it easy to obtain high performance. The positive electrode active material may be used as a single type or as a combination of two or more types. The positive electrode active material may be in the form of particles, for example, and its size is not particularly limited. The particles of the positive electrode active material may be solid particles, hollow particles, or particles having pores. The particles of the positive electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size (D50) of the particles of the positive electrode active material may, for example, be 1 nm or more, 5 nm or more, or 10 nm or more, or 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. In addition, the average particle size D50 referred to herein is the particle size (median diameter) at 50% of the cumulative value in the volume-based particle size distribution obtained by the laser diffraction and scattering method.

[0048] The surface of the positive electrode active material may be coated with an ion-conducting oxide. That is, the positive electrode active material layer (10) may include a composite having the positive electrode active material and an ion-conducting oxide coating its surface. This makes it easier to suppress reactions between the positive electrode active material and sulfides (e.g., the sulfide solid electrolyte described later). Examples of ion-conducting oxides that coat and protect the surface of the positive electrode active material include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, and Li4Ti5O. 12Examples include at least one selected from Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, and Li2WO4. The coverage ratio (area ratio) of the ion-conducting oxide on the surface of the positive electrode active material may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the ion-conducting oxide layer may be, for example, 0.1 nm or more or 1 nm or more, or 100 nm or less or 20 nm or less.

[0049] 1.1.2 Electrolytes

[0050] The electrolyte that may be included in the positive electrode active material layer (10) may be a solid electrolyte, a liquid electrolyte (electrolyte), or a combination thereof. In particular, when the positive electrode active material layer (10) includes a solid electrolyte (especially a sulfide solid electrolyte), a higher effect can be expected according to the technology of the present disclosure.

[0051] The solid electrolyte may be one known as a solid electrolyte for secondary batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include oxide solid electrolytes and sulfide solid electrolytes. Among inorganic solid electrolytes, sulfide solid electrolytes, and among them, sulfide solid electrolytes containing at least Li, S, and P as constituent elements, exhibit high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be in the form of particles. The average particle size (D50) of the solid electrolyte may be, for example, 10 nm or more and 10 μm or less. The ionic conductivity of the solid electrolyte at 25°C is, for example, 1 × 10⁻⁶ -4 S / cm or more, or, 1 × 10⁻⁶ -3It may be S / cm or higher. A single type of solid electrolyte may be used alone, or two or more types may be used in combination.

[0052] Oxide solid electrolytes include lithium lanthanum zirconate, LiPON, and Li 1＋X Al X Ge 2-X It may be one or more types selected from (PO4)3, Li-SiO glass, Li-Al-SO glass, etc.

[0053] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic-based sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Sulfide glass is amorphous. Sulfide glass may have a glass transition temperature (Tg). Also, when the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phases include, for instance, a Thio-LISICON type crystalline phase, an LGPS type crystalline phase, and an azirodite type crystalline phase.

[0054] The sulfide solid electrolyte may contain, for example, the element Li, the element X (where X is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In), and the element S. Additionally, the sulfide solid electrolyte may additionally contain at least one of the element O and the halogen element. Additionally, the sulfide solid electrolyte may contain the element S as a main component of the anion element.

[0055] Sulfide solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-GeS2, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-LiI-LiBr, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are defined numbers and Z is any one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are defined numbers. M is any one of P, Si, Ge, B, Al, Ga, In.) It may be at least one type selected from.

[0056] The composition of the sulfide solid electrolyte is not particularly limited, but examples include xLi2S·(100-x)P2S5(70≤x≤80), yLiI·zLiBr·(100-yz)(xLi2S·(1-x)P2S5) (0.7≤x≤0.8, 0≤y≤30, 0≤z≤30), etc. Alternatively, the sulfide solid electrolyte is of the general formula: Li 4-x Ge 1-x P xIt may have a composition represented by S4 (0 < x < 1). In the above general formula, at least a portion of Ge may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, at least a portion of P may be substituted with at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. In the above general formula, a portion of Li may be substituted with at least one of Na, K, Mg, Ca, and Zn. In the above general formula, a portion of S may be substituted with a halogen (at least one of F, Cl, Br, and I). Alternatively, the sulfide solid electrolyte may be Li 7-a PS 6-a X a It may have a composition represented as (where X is at least one of Cl, Br, and I, and a is a number between 0 and 2). a may be 0 or greater than 0. In the latter case, a may be 0.1 or greater, 0.5 or greater, or 1 or greater. Also, a may be 1.8 or less, or 1.5 or less.

[0057] The electrolyte may, for example, contain lithium ions as carrier ions. The electrolyte may, for example, be a non-aqueous electrolyte. For example, a lithium salt dissolved in a carbonate-based solvent at a predetermined concentration may be used as the electrolyte. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), dimethyl carbonate (DMC), etc. Examples of lithium salts include hexafluorophosphate, etc.

[0058] 1.1.3 Challenge Aids

[0059] Examples of conductive aids that may be included in the positive electrode active material layer (10) include carbon materials such as vapor phase carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), or carbon nanofibers (CNF); and metal materials such as nickel, aluminum, and stainless steel. The conductive aid may be in the form of particles or fibers, for example, and its size is not particularly limited. Only one type of conductive aid may be used alone, or two or more types may be used in combination.

[0060] 1.1.4 Binder

[0061] Examples of binders that may be included in the positive electrode active material layer (10) 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, polyacrylic acid-based binders, etc. Only one type of binder may be used alone, or two or more types may be used in combination.

[0062] 1.2 Solid Electrolyte Layer

[0063] The solid electrolyte layer (20) comprises at least a solid electrolyte. The solid electrolyte included in the solid electrolyte layer (20) may be of the same type as or a different type from the solid electrolyte that may be included in the positive electrode active material layer (10) described above. In particular, when the solid electrolyte layer (20) comprises an inorganic solid electrolyte, a higher effect can be expected from the technology of the present disclosure. Examples of inorganic solid electrolytes include the oxide solid electrolyte or sulfide solid electrolyte described above. Among inorganic solid electrolytes, in particular, sulfide solid electrolytes, and among them, sulfide solid electrolytes containing at least Li, S, and P as constituent elements, have high performance. Specific examples of oxide solid electrolytes or sulfide solid electrolytes are as described above. The solid electrolyte layer (20) may additionally optionally include a binder or various additives. The binder that may be included in the solid electrolyte layer (20) may be of the same type as or a different type from the binder that may be included in the positive electrode active material layer (10) described above. In the solid electrolyte layer (20), the solid electrolyte or the binder may each be used as a single type or as a combination of two or more types. The solid electrolyte layer (20) may be formed entirely of solid, or it may contain a solid electrolyte and a liquid. The content of the solid electrolyte and binder, etc., in the solid electrolyte layer (20) is not particularly limited. For example, with the entire solid electrolyte layer (20) (total solid content) set to 100 mass%, the content of the solid electrolyte may be 50 mass% or more, 60 mass% or more, or 70 mass% or more, or 100 mass% or less, or 90 mass% or less. The thickness of the solid electrolyte layer (20) is not particularly limited and, for example, may be 0.1 μm or more or 1 μm or more, or 2 mm or less or 1 mm or less.

[0064] 1.3 Negative electrode active material layer

[0065] As shown in FIG. 1, the negative electrode active material layer (30) comprises a first material (31) and a second material (32). The first material (31) is at least one of an alloy of Li and element X, and a compound of Li and said element X. The second material (32) is at least one of a unit of metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M. Here, the generation energy E of the first material (31) LiX E is the formation energy of a compound of metal element M and element X. MX Lower than.

[0066] As shown in FIG. 3, when the secondary battery (101) is discharged, Li ions are released from the first material (31) (an alloy or compound of Li and metal element M) or the second material (32) (an alloy or compound of Li and element X) included in the negative electrode active material layer (30) to the positive electrode side, and the volume of the negative electrode active material layer (30) may change. The Li ions released from the negative electrode active material layer (30) reach the positive electrode active material layer (10) through the solid electrolyte layer (20) and may be absorbed by the positive electrode active material included in the positive electrode active material layer (10). As shown in FIG. 3, the secondary battery (101) may have the same configuration as the secondary battery (102) related to the second form described later after discharge. Alternatively, the secondary battery (101) may be controlled to stop discharging before reaching the same configuration as the secondary battery (102) related to the second form described later. In other words, the secondary battery (101) after discharge may have a compound of metal element M and element X between the solid electrolyte layer (20) and the negative electrode current collector (50), or may have a negative electrode active material layer (30).

[0067] When charging the secondary battery (101), Li ions are released from the positive electrode active material layer (10). Specifically, the Li ions released from the positive electrode active material layer (10) reach the space between the solid electrolyte layer (20) and the negative electrode current collector (50) via the solid electrolyte layer (20), and may be precipitated as a second material (32) or metallic lithium, etc. As shown in FIGS. 1 and 3, in the secondary battery (101) after charging, a negative electrode active material layer (30) may be formed between the solid electrolyte layer (20) and the negative electrode current collector (50). The negative electrode active material layer (30) includes the first material (31) and the second material (32) described above. The thickness of the negative electrode active material layer (30) after charging is not specifically limited, and for example, it may be 0.1 μm or more or 1 μm or more, or 2 mm or less or 1 mm or less. The amount of metallic lithium deposited between the solid electrolyte layer (20) and the negative electrode current collector (50) is not specifically limited and can be appropriately adjusted according to the intended battery performance. However, if the amount of metallic lithium deposited is excessively large, there is a concern about pressure concentration, etc. In this regard, as a standard for the amount of metallic lithium deposited, the amount may be such that the charging capacity of the secondary battery (101) is, for example, 1 mAh / ㎠ or more or 5 mAh / ㎠ or less.

[0068] 1.3.1 First Material

[0069] The first material (31) is at least one of an alloy of Li and element X, and a compound of Li and said element X. That is, in the first material (31), element X may be dissolved in metal Li or may be combined with metal Li. In one embodiment, the negative electrode active material layer (30) includes a compound of Li and said element X as the first material (31). In one embodiment, the negative electrode active material layer (30) includes an alloy of Li and said element X as the first material (31). The molar ratio of Li and element X is not particularly limited and depends on the type of element X or the first material (31).

[0070] Energy E of the first substance (31) LiX E is the formation energy of a compound of metal element M and element X. MX It is lower than. In other words, element X has relatively high reactivity with Li and relatively low reactivity with metal element M. As long as these conditions are satisfied, there is no particular restriction on the type of element X constituting the first material (31). Element X may be a metal element or a non-metal element. For example, if element X is at least one of H, B, and P, the first material (31) has excellent lithium ion conductivity, and the performance of the secondary battery (101) is likely to be higher. For example, the first material (31) may be at least one selected from a compound of Li and B, a compound of Li and P, a compound of Li and H, a complex compound thereof, and a mixture thereof. Alternatively, if the metal element M described later is Mg, and also the element X is at least one of Bi, Sb, In, Sn, H, I, Ga, Te, Hg, Cd, Si, B, As, Zn, Ge, Br, P and Se, the performance of the secondary battery (101) is more likely to be higher.

[0071] The shape of the first material (31) or the location of the first material (31) in the negative electrode active material layer (30) is not particularly limited. The first material (31) may be in the form of particles, may be in the form of layers (including those formed by the aggregation of multiple particles), may be in the form of films (including those formed by the aggregation of multiple particles), or may be irregular. The first material (31) may be dispersed or localized in the negative electrode active material layer (30). In particular, high performance is easily secured when the negative electrode active material layer (30) includes the first material (31) formed in the form of films, and the thickness of the first material (31) formed in the form of films is 10 nm or more and 50 μm or less. The thickness may be 30 nm or more and 40 μm or less, 50 nm or more and 30 μm or less, 70 nm or more and 20 μm or less, or 100 nm or more and 10 μm or less. Also, the thickness may be 0.05% or more and 100% or less of the total thickness of the negative electrode active material layer (30), or 1% or more and less than 100%. When the negative electrode active material layer (30) includes the first material (31) formed as a film, the first material (31) formed as a film may or may not be in contact with the negative electrode current collector (50). Also, the first material (31) formed as a film may or may not be in contact with the solid electrolyte layer (20). In particular, when the first material (31) formed as a film is in contact with the negative electrode current collector (50), in other words, when the first material (31) formed as a film covers the surface of the negative electrode current collector (50), the first material (31) can also function as a protective film, making it easy to secure high performance.The area of ​​the first material (31) formed in the above film may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 99% or more of the area of ​​the negative electrode active material layer (30) (the area of ​​the surface of the negative electrode active material layer (30) that faces the negative electrode current collector (50).

[0072] The amount of the first material (31) in the negative electrode active material layer (30) is not particularly limited. For example, the negative electrode active material layer (30) may contain more than 0 mass% and less than or equal to 80 mass% of the first material (31). The amount of the first material (31) may be 0.01 mass% or more and less than or equal to 70 mass%, 0.1 mass% or more and less than or equal to 60 mass%, 1 mass% or more and less than or equal to 50 mass%, or 10 mass% or more and less than or equal to 40 mass%.

[0073] 1.3.2 Secondary Substance

[0074] The second material (32) is at least one of the following: a single metal element M, an alloy of Li and the metal element M, and a compound of Li and the metal element M. That is, in the second material (32), the metal element M may exist as a single element without being combined with other elements, may be dissolved in metal Li, or may be combined with metal Li. In one embodiment, the negative electrode active material layer (30) includes a compound of Li and the metal element M as the second material (32). In one embodiment, the negative electrode active material layer (30) includes an alloy of Li and the metal element M as the first material (31). The molar ratio of Li and the metal element M is not particularly limited and depends on the type of metal element M or the second material (32).

[0075] As described above, the generation energy E of the first substance (31) LiXE is the formation energy of a compound of metal element M and element X. MX It is lower than. In other words, in the negative electrode active material layer (30), the first material (31) and the second material (32) are likely to exist stably, respectively. That is, the reaction between the element X constituting the first material (31) and the metal element M constituting the second material (32) is likely to be suppressed by Li. As long as these conditions are satisfied, there is no particular restriction on the type of metal element M constituting the second material (32). The metal element M can be any element capable of alloying with Li. In particular, when the metal element M is at least one of Mg, Sn, Zn, In, Al, Fe, Ni, Mn, Cr, Ag, Ga, Si, Sb, Pb, Bi, Cd, Sr, Ge, and As, and among them, when the metal element M is Mg, the relationship of the above generation energy is satisfied, and the precipitation and dissolution reactions of Li during charging and discharging are likely to be uniform, and high performance is likely to be secured. For example, the second material (32) may be Mg alone, an alloy of Li and Mg, or a compound of Li and Mg.

[0076] The shape of the second material (32) or the location of the second material (32) in the negative electrode active material layer (30) is not particularly limited. The second material (32) may be in the form of particles, may be in the form of layers (including those in which multiple particles are aggregated in a planar manner), may be in the form of films (including those in which multiple particles are aggregated in a planar manner), or may be irregular. The second material (32) may be dispersed or localized in the negative electrode active material layer (30). In particular, high performance is easily secured when the negative electrode active material layer (30) includes the second material (32) formed in layers, and the thickness of the layer of the second material (32) is 100 nm or more and 500 μm or less. When the negative electrode active material layer (30) includes the second material (32) formed in a layered manner, the layer of the second material (32) may or may not be in contact with the solid electrolyte layer (20). In addition, the layer of the second material (32) may or may not be in contact with the negative electrode current collector (50). In particular, when the layer of the second material (32) is in contact with the solid electrolyte layer (20), the precipitation and dissolution reactions of Li during charging and discharging are easily homogenized, and high performance is easily secured. The area of ​​the layer of the second material (32) may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, or 99% or more of the area of ​​the negative electrode active material layer (30) (the area of ​​the surface of the negative electrode active material layer (30) that faces the solid electrolyte layer (20)).

[0077] The amount of the second material (32) in the negative electrode active material layer (30) is not particularly limited. For example, the negative electrode active material layer (30) may contain 1 mass% or more and less than 100 mass% of the second material (32).

[0078] 1.3.3 Supplementary for Metallic Element M and Element X

[0079] In the case of the secondary battery (101), higher performance is easily secured when the metal element M and the element X satisfy the following relationships (1) and (2). That is, when the following relationships (1) and (2) are satisfied, when the secondary battery (101) is charged, the compound of metal element M and element X is decomposed by the conversion reaction described later, and when the secondary battery (101) is discharged, the reverse reaction of the conversion reaction occurs, and it is easy to return to the compound of metal element M and element X.

[0080] (1) Energy E of the formation of the compound of the metal element M and the element X MX a, Formation energy E of the compound of Li and the metal element M LiM Lower than.

[0081] (2) Formation energy E of the compound of Li and the element X LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than.

[0082] In the secondary battery (101), the generated energy E MX and generation energy E LiX It is thought that a larger difference makes it easier to secure a superior effect. In this regard, for the secondary battery (101), the generated energy E MX and generation energy E LiX The difference E MX - E LiX a, 0.027 eV / atom or more, 0.032 eV / atom or more, 0.050 eV / atom or more, 0.075 eV / atom or more, 0.100 eV / atom or more, 0.150 eV / atom or more, or, 0.200 eV / atom or more. Also, generation energy E MX , generation energy ELiM , and, generation energy E LiX This can be verified in various databases.

[0083] 1.3.4 Other Components

[0084] The negative electrode active material layer (30) may include other components in addition to the first material (31) and the second material (32). For example, the negative electrode active material layer (30) may include a compound of metal element M and element X as unreacted material of the conversion reaction described later. Also, the negative electrode active material layer (30) may include metallic lithium precipitated during charging. Here, "metallic lithium" is a concept that includes lithium alloys in addition to lithium alone. That is, the negative electrode active material layer (30) may include lithium alone or lithium alloys. The second material (32) may be an example of a lithium alloy. Alternatively, the negative electrode active material layer (30) may include, in addition to the second material (32), at least one lithium alloy selected from, for example, 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. The lithium alloy may be only one type or two or more types.

[0085] 1.4 Other Components

[0086] The secondary battery (101) may have at least each of the above configurations, and may have other configurations. The configuration described below is an example of other configurations that the secondary battery (101) may have.

[0087] 1.4.1 Entire Drama House

[0088] As shown in FIG. 1, the secondary battery (101) may be equipped with a positive electrode current collector (40) that is in contact with a positive electrode active material layer (10). Any material capable of functioning as a positive electrode current collector of the secondary battery may be used for the positive electrode current collector (40). The positive electrode current collector (40) may be a metal foil or a metal mesh. In particular, metal foil has excellent handling properties. The positive electrode current collector (40) may be made of multiple sheets of metal foil. Examples of metals constituting the positive electrode current collector (40) include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. In particular, from the perspective of ensuring oxidation resistance, the positive electrode current collector (40) may contain Al. The positive electrode current collector (40) may have any coating layer on its surface for the purpose of adjusting resistance, etc. Also, when the positive electrode current collector (40) is made of multiple metal foils, it may have any layer between the multiple metal foils. The thickness of the positive electrode current collector (40) 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.

[0089] 1.4.2 Bu-geuk entire house

[0090] As shown in FIG. 1, the secondary battery (101) may be equipped with a negative current collector (50) that is in contact with a negative active material layer (30). Any material capable of functioning as a negative current collector of the secondary battery may be used for the negative current collector (50). The negative current collector (50) may be a metal foil or a metal mesh, or a carbon sheet. In particular, metal foil has excellent handling properties. The negative current collector (50) may be made of multiple metal foils or sheets. Examples of metals constituting the negative current collector (50) include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. In particular, from the perspective of ensuring reduction resistance and difficulty in alloying with lithium, the negative electrode current collector (50) may comprise at least one metal selected from Cu, Ni, and stainless steel, and among them, may comprise at least one metal among Ni and stainless steel. The negative electrode current collector (50) may have any coating layer on its surface. Also, if the negative electrode current collector (50) is made of multiple metal foils, it may have any layer between the multiple metal foils. The thickness of the negative electrode current collector (50) 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.

[0091] In the secondary battery (101), the negative electrode current collector (50) may have any protective layer on its surface. For example, the negative electrode current collector (50) may have a conductive substrate selected from the metal foil, metal mesh, or carbon sheet and a protective layer formed on the surface of the conductive substrate, and the protective layer may be disposed between the conductive substrate and the negative electrode active material layer (30) described above. The protective layer may, for example, contain Mg and may not contain a compound of Mg and element X. It is believed that by having a protective layer containing Mg on the negative electrode current collector (50), the diffusion of Li on the surface of the negative electrode current collector (50) is promoted, and the affinity of metallic lithium for the negative electrode current collector (50) is increased, so that the void between the negative electrode current collector (50) and the metallic lithium is suppressed, and metallic lithium is deposited more uniformly on the surface of the negative electrode current collector (50).

[0092] The protective layer may be a layer in which the molar ratio of Mg is the highest among all constituent elements. The molar ratio of Mg in the entire protective layer may be, for example, 50 mol% or more and 100 mol% or less, or 70 mol% or more, 80 mol% or more, or 90 mol% or more. The protective layer may be, for example, either a metal thin film containing Mg (e.g., a deposited film) or a layer containing Mg particles. Alternatively, the protective layer may be a layer containing only Mg particles. The metal thin film containing Mg may be composed of Mg or a Mg alloy. Furthermore, the Mg particles may be particles of Mg alone or particles containing Mg and elements other than Mg. Examples of elements other than Mg include various metallic elements, metalloid elements, or non-metallic elements. For example, the Mg particles may be alloy particles containing Mg and metals other than Mg (Mg alloy particles). The Mg alloy particles may be an alloy containing Mg as a main component (an alloy in which 50 mol% or more of the total constituent elements is Mg). The Mg alloy particles may contain at least one of, for example, Li, Au, Al, and Ni as a metal M other than Mg. The Mg alloy particles may or may not contain Li. The Mg alloy particles may contain a β single-phase alloy of Li and Mg. Alternatively, the Mg particles may be oxide particles containing Mg and O (Mg oxide particles). The Mg oxide particles may be, for example, oxide particles composed only of Mg and O, or composite oxide particles represented as Mg-M'-O (where M' is at least one of Li, Au, Al, and Ni). When the Mg oxide particles contain M', it is preferable that M' contains at least Li. M' may or may not contain a metal other than Li.In the former case, M' may be one type of metal other than Li, or two or more types. The Mg particles may be primary particles or secondary particles formed by the aggregation of primary particles. The average particle size (D50) of the Mg particles may be, for example, 100 nm or more and 100 μm or less, 200 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, 600 nm or more, 700 nm or more, or 800 nm or more, or 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

[0093] The thickness of the protective layer may be, for example, 10 nm or more and 10 μm or less. The thickness of the protective layer may be 50 nm or more or 100 nm or more, or 5 μm or less, 3 μm or less, 1 μm or less, or 700 nm or less. In the secondary battery (101), the negative electrode current collector (50) may not have a protective layer, may have only one layer of protective layer, or may have two or more layers. As a method for forming the protective layer, a method of depositing a protective layer on the surface of the conductive substrate constituting the negative electrode current collector (50) or a method of pressing Mg particles may be used. As a method of depositing a protective layer on the surface of the conductive substrate, for example, a PVD method such as a deposition method or a sputtering method, or a plating method such as an electrolytic plating method or an electroless plating method, or a coating method using a slurry may be employed.

[0094] 1.4.3 External body

[0095] The secondary battery (101) may have each of the above components housed inside an outer body. More specifically, the portion excluding the tab or terminal for extracting power from the secondary battery (101) to the outside may be housed inside an outer body. Any known external body for a battery may be adopted as the external body. For example, a laminate film may be used as the external body. In addition, a plurality of secondary batteries (101) may be electrically connected and optionally overlapped to form a battery cell. In this case, the battery cell may be housed inside a known battery case.

[0096] 1.4.4 Bag Resin

[0097] In the secondary battery (101), each of the above components may be encapsulated by a resin. For example, at least the side surface (side along the stacking direction) of each layer shown in FIG. 1 may be encapsulated by a resin. This makes it easier to suppress the incorporation of moisture into the interior of each layer. As the encapsulating resin, known curable resins or thermoplastic resins may be used.

[0098] 1.4.5 Absence of Restraint

[0099] The secondary battery (101) may have a restraining member for restraining each of the above components in the thickness direction. As a restraining pressure is applied by the restraining member, the internal resistance of the battery is easily reduced. There is no particular limitation on the restraining pressure by the restraining member. The restraining pressure by the restraining member may be 5 MPa or less, 3 MPa or less, or 1 MPa or less.

[0100] 2. Secondary battery (second type)

[0101] FIG. 2 shows the configuration of a secondary battery (102) related to a second type. As shown in FIG. 2, the secondary battery (102) comprises a positive electrode active material layer (10), a solid electrolyte layer (20), a negative electrode current collector (50), and metallic lithium that is deposited between the solid electrolyte layer (20) and the negative electrode current collector (50) upon charging. Between the solid electrolyte layer (20) and the negative electrode current collector (50), a compound (33) of a metal element M and an element X exists. Here, the generation energy E of the compound (33) of the metal element M and the element X MX is the generation energy E of the compound of Li and the element X (corresponding to the first substance (31) in the first form). LiX It is higher than.

[0102] 2.1 Positive electrode active material layer, solid electrolyte layer, and negative electrode current collector

[0103] The positive electrode active material layer (10), the solid electrolyte layer (20), and the negative electrode current collector (50) may be the same as those in the first form. As shown in FIG. 3, when charging the secondary battery (102), Li ions emitted from the positive electrode active material layer (10) reach the space between the solid electrolyte layer (20) and the negative electrode current collector (50) via the solid electrolyte layer (20), receive electrons, and precipitate as metallic lithium. Also, when discharging the battery, the metallic lithium between the solid electrolyte layer (20) and the negative electrode current collector (50) is dissolved (ionized) and returned to the positive electrode active material layer (10).

[0104] 2.2 Metallic Lithium as a Negative Electrode Active Material

[0105] The secondary battery (102) is equipped with a lithium precipitation type negative electrode. Specifically, as shown in FIGS. 2 and 3, metallic lithium is precipitated between the solid electrolyte layer (20) and the negative electrode current collector (50) by charging. The metallic lithium precipitated between the solid electrolyte layer (20) and the negative electrode current collector (50) is dissolved (ionized) during discharge and returned to the positive electrode active material layer (10). Here, "metallic lithium" is a concept that includes lithium alloys in addition to lithium alone. That is, in the secondary battery (102), metallic lithium may be precipitated as lithium alone or as an alloy together with other metals. Specific examples of lithium alloys are as described above. In the secondary battery (102), a predetermined compound (33) exists between the solid electrolyte layer (20) and the negative electrode current collector (50). In this case, when charging, a conversion reaction of the compound (33) occurs due to lithium supplied from the positive electrode active material layer (10) to the solid electrolyte layer (20) and the negative electrode current collector (50), thereby producing a compound or alloy of lithium and element X (equivalent to the first material (31)) and producing a fresh metal M (equivalent to the second material (32)), and furthermore, the fresh metal M and lithium may be alloyed to form a lithium alloy as metallic lithium (equivalent to the second material (32)), or a compound of metal element M and Li (equivalent to the second material (32)).

[0106] 2.3 Compounds of Metal Element M and Element X

[0107] A compound (33) of metal element M and element X exists between the solid electrolyte layer (20) and the negative electrode current collector (50). Here, the generation energy E of the compound (33) of metal element M and element X MX is the energy E of formation of a compound of Li and element X (equivalent to the first substance (31)). LiXIt is higher than that of the compound of Li and element X. That is, the compound of Li and element X is more likely to be formed than the compound of metal element M and element X (33). Therefore, when Li ions are supplied between the solid electrolyte layer (20) and the negative electrode current collector (50) during the charging of the secondary battery (102), the compound (33) existing between the solid electrolyte layer (20) and the negative electrode current collector (50) is decomposed by the conversion reaction represented by the following reaction equation (1), and a fresh metal M (equivalent to the second material (32)) is produced along with the compound of Li and element X (equivalent to the first material (31)). If charging is continued, this fresh metal element M and Li undergo an alloying reaction represented by the following reaction equation (2), and a lithium alloy as metal lithium (equivalent to the first material (31)) or a compound of metal element M and Li (equivalent to the second material (32)) is precipitated.

[0108] MX+Li⇒LiX+M··· (1)

[0109] Li+M⇒LiM ··· (2)

[0110] The metal element M only needs to satisfy the relationship of the generation energy above and be capable of carrying out the conversion reaction above. The metal element M only needs to be an element capable of alloying with Li. In particular, when the metal element M is at least one of Mg, Sn, Zn, In, Al, Fe, Ni, Mn, Cr, Ag, Ga, Si, Sb, Pb, Bi, Cd, Sr, Ge, and As, and among these, when the metal element M is Mg, the precipitation and dissolution reactions of Li during charging and discharging tend to be homogenized, and high performance tends to be secured.

[0111] Element X also satisfies the relationship of the generation energy above and can carry out the conversion reaction. Element X may be a metallic element or a non-metallic element. In particular, if the product after the conversion reaction (the first material (31)) has excellent lithium ion conductivity, the performance of the secondary battery is more likely to be higher. Considering the more efficient generation of the conversion reaction and the generation of a product with excellent lithium ion conductivity, element X may be at least one of H, B, and P. Alternatively, if the metallic element M is Mg, higher performance is more likely to be secured when element X is at least one of Bi, Sb, In, Sn, H, I, Ga, Te, Hg, Cd, Si, B, As, Zn, Ge, Br, P, and Se.

[0112] The compound (33) of metal element M and element X may be at least one selected from compounds of Mg and B (e.g., magnesium boride: MgB2), compounds of Mg and P (e.g., magnesium phosphide: Mg3P2), compounds of Mg and H (e.g., magnesium hydride: MgH2), complex compounds thereof, and mixtures thereof.

[0113] In the case of the secondary battery (102), just like the secondary battery (101), higher performance is more easily secured when the metal element M and the element X satisfy the following relationships (1) and (2). That is, when the following relationships (1) and (2) are satisfied, when the secondary battery (102) is charged, the compound of metal element M and element X is decomposed by the conversion reaction described above, and when the secondary battery (102) is discharged, the reverse reaction of the conversion reaction occurs, and it is easy to return to the compound of metal element M and element X.

[0114] (1) Energy E of the formation of the compound of the metal element M and the element X MX a, Formation energy E of the compound of Li and the metal element M LiM Lower than.

[0115] (2) Formation energy E of the compound of Li and the element X LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than.

[0116] The shape of the compound (33) of metal element M and element X is not particularly limited and may be a thin film or a layer, may be particulate, or may be a layer containing particulate compound (33). As described in detail in the manufacturing method of the secondary battery (101, 102), the compound (33) may cover the surface of the negative electrode current collector (50). Also, as shown in FIG. 2, the compound (33) may be in contact with the solid electrolyte layer (20) before the conversion reaction. When the compound (33) is in the form of particles, the average particle size (D50) may be, for example, 100 nm or more and 100 μm or less, 200 nm or more, 400 nm or more, 600 nm or more, 800 nm or more, 1 μm or more, 5 μm or more, or 10 μm or more, or 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The amount of compound (33) between the solid electrolyte layer (20) and the negative electrode current collector (50) is not particularly limited and can be appropriately determined considering the battery performance. For example, when a compound (33) exists as a thin film or layer between a solid electrolyte layer (20) and a negative electrode current collector (50), the thickness may be 10 nm or more and 100 μm or less, 20 nm or more, 30 nm or more, 40 nm or more, 100 nm or more, 200 nm or more, 400 nm or more, 600 nm or more, 800 nm or more, 1 μm or more, 5 μm or more, or 10 μm or more, or 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 10 μm or less, 1 μm or less, or 800 nm or less. Also, when a layer made of particles of the compound (33) is formed between the solid electrolyte layer (20) and the negative electrode current collector (50), the number of particles in the thickness direction of the layer may be one or more.

[0117] In the case of the secondary battery (102), just like the secondary battery (101), the generated energy E MX and generation energy E LiX It is thought that the larger the difference, the easier it is to proceed with the conversion reaction described above and to secure the above effect. In this regard, regarding the secondary battery (102), the generated energy E MX and generation energy E LiX The difference E MX - E LiX a, 0.027 eV / atom or higher, 0.032 eV / atom or higher, 0.050 eV / atom or higher, 0.075 eV / atom or higher, 0.100 eV / atom or higher, 0.150 eV / atom or higher, or, 0.200 eV / atom or higher.

[0118] 2.4 Compounds of Li and Element X

[0119] As described above, in a secondary battery (102), a compound of Li and element X can be produced by a conversion reaction of a compound (33) of a metal element M and element X. The type of compound of Li and element X depends on the type of compound (33). As described above, when element X is at least one of H, B, and P, the conversion reaction of the compound (33) can be generated more efficiently, and a product with excellent lithium ion conductivity can be produced. That is, the compound of Li and element X may be at least one selected from a compound of Li and B, a compound of Li and P, a compound of Li and H, a complex compound thereof, and a mixture thereof. The shape of the compound of Li and element X also depends on the shape of the compound (33). That is, the shape of the compound of Li and element X can be a thin film or a layer, as described above, or it can be a particle, or it can be a layer containing a particle compound. The amount of the compound of Li and element X between the solid electrolyte layer (20) and the negative electrode current collector (50) after the conversion reaction also depends on the amount of the compound (33). The compound of Li and element X may, for example, cover the surface of the negative electrode current collector (50) to protect the negative electrode current collector (50).

[0120] 2.5 Other Components

[0121] The secondary battery (102) may have at least each of the above configurations, and may have other configurations. The other configurations are the same as those described in the first embodiment. For example, the secondary battery (102) may have a positive electrode current collector (40). Also, the secondary battery (102) may have a predetermined outer body. Also, the secondary battery (102) may have a predetermined encapsulation resin. Also, the secondary battery (102) may have a predetermined restraining member.

[0122] 3. Operations and Effects by Secondary Batteries (Type 1 and Type 2)

[0123] According to the findings of the inventors, in a conventional secondary battery equipped with a metallic lithium negative electrode, when the deposition and dissolution of metallic lithium are repeated between the solid electrolyte layer and the negative electrode current collector, the metallic lithium is deposited and dissolved unevenly, and voids are generated between the solid electrolyte layer and the metallic lithium, resulting in a decrease in Coulomb efficiency. Furthermore, if the metallic lithium is deposited and dissolved unevenly, in addition to increasing the resistance of the secondary battery, the cycle characteristics are also prone to deterioration. In contrast, according to the secondary battery (101, 102) of the present disclosure, for example, it is thought that voids during the deposition of metallic lithium can be suppressed, and thus Coulomb efficiency and the like can be improved. Specifically, it is as follows.

[0124] 3.1 Operation and Effects by Secondary Battery (Type 1)

[0125] As shown in FIG. 3, when the secondary battery (101) is discharged, the second material (32) releases Li ions, and along with this, fresh metal M is generated. The fresh metal M functions as a deposition site for metallic lithium (second material (32)) when the secondary battery (101) is charged, and the metallic lithium is easily deposited uniformly, smoothly, and efficiently. By suppressing the non-uniformity of the deposition of metallic lithium, the secondary battery (101) has excellent Coulomb efficiency. Also, as shown in FIG. 3, when the secondary battery (101) is discharged, the first material (31) may release Li ions, or it may remain as the first material (31). When the first material (31) releases Li ions, the remaining element X can react with the fresh metal M described above. Thus, a compound (33) (MX) of metal element M and element X can be produced. When charging the secondary battery (101), the compound (33) reacts with Li ions to cause the conversion reaction described above, thereby producing the first material (31) (LiX) and fresh metal M. As described above, the fresh metal M functions as a precipitation site for metallic lithium, and when charging the secondary battery (101), metallic lithium (second material (32)) is uniformly and smoothly precipitated.

[0126] As described above, when the secondary battery (101) is charged and discharged, the negative electrode active material layer (30) contains fresh metal M, which becomes a precipitation site for metallic lithium during charging. That is, when the secondary battery (101) is charged, metallic lithium (Li-M alloy) can be precipitated uniformly, smoothly, and even efficiently starting from this fresh metal M. In addition, the affinity of the precipitated Li to the solid electrolyte layer (20) is increased, making it easier to suppress voids formed at the interface between the solid electrolyte layer (20) and the precipitated Li. In addition, voids in the negative electrode active material layer (30) are also easier to suppress. In this way, as the non-uniformity of the precipitation of metallic lithium is suppressed, the secondary battery (101) has excellent Coulomb efficiency. In addition, when the first material (31) (LiX) and the second material (fresh metal M) are generated in the negative electrode active material layer (30) by the above conversion reaction, the layer composed of said LiX and fresh metal M has a containment structure, and it can be expected that the volume change of the secondary battery during charging and discharging will be reduced.

[0127] 3.2 Functions and Effects by Secondary Batteries (Type 2)

[0128] As described above, when charging the secondary battery (102), a compound (33) of metal element M and element X reacts with Li ions, and through the conversion reaction, fresh metal M can be generated between the solid electrolyte layer (20) and the negative electrode current collector (50) (for example, the interface between the solid electrolyte layer (20) and the compound (33), or the interface between the solid electrolyte layer (20) and the compound of Li and element X (first material (31))), and metallic lithium can be uniformly, smoothly, and efficiently deposited starting from the fresh metal M between the solid electrolyte layer (20) and the negative electrode current collector (50). Therefore, it is thought that the void between the solid electrolyte layer (20) and the negative electrode current collector (50) can be suppressed during the deposition of metallic lithium. In addition, it is thought that the affinity of metallic lithium for the solid electrolyte layer (20) is easily increased, and voids at the interface between the solid electrolyte layer (20) and the metallic lithium can also be suppressed. In this way, by suppressing voids between the solid electrolyte layer (20) and the negative electrode current collector (50), non-uniformity of reaction during charging and discharging is eliminated, and the Coulomb efficiency as a secondary battery is easily improved. Furthermore, when LiX and fresh metal M are generated between the solid electrolyte layer (20) and the negative electrode current collector (50) by the above conversion reaction, the layer consisting of said LiX and fresh metal M has a containment structure, and it can be expected that the volume change of the secondary battery during charging and discharging will be reduced.

[0129] 3.3 Supplement

[0130] In addition, although the above description focused on the structural features of the secondary battery (101, 102) of the present disclosure, the secondary battery (101, 102) may be specified as follows in terms of its function.

[0131] The secondary battery (101) related to the first form may be configured such that, for example, during discharge, the element X of the first material (31) and the metal element M of the second material (32) react to form a compound (33) of the metal element M and the element X. More specifically, the secondary battery (101) may be configured such that during discharge, the element X of the first material (31) and the metal element M of the second material (32) react to form a compound (33) of the metal element M and the element X on one or both of the surface of the solid electrolyte layer (20) and the surface of the negative electrode current collector (50). In one embodiment, the secondary battery (101) may be configured such that, during discharge, the element X of the first material (31) and the metal element M of the second material (32) react to form a compound (33) of the metal element M and the element X on the surface of the negative electrode current collector (50).

[0132] The secondary battery (102) related to the second form may be configured such that, for example, the compound (33) of the metal element M and the element X decomposes during charging, and a compound of Li and the element X is formed. More specifically, the secondary battery (102) may be configured such that, during charging, the compound (33) of the metal element M and the element X decomposes, and a compound of Li and the element X is formed on one or both of the surface of the solid electrolyte layer (20) and the surface of the negative electrode current collector (50). In one embodiment, the secondary battery (102) may be configured such that, during charging, the compound (33) of the metal element M and the element X decomposes, and a compound of Li and the element X (first material (31)) is formed on the surface of the negative electrode current collector (50).

[0133] As shown in FIGS. 1 to 3, the secondary battery of the present disclosure may have different structures before and after the conversion reaction. That is, before the conversion reaction (e.g., before charging), a compound (33) of metal element M and element X may exist between the solid electrolyte layer (20) and the negative electrode current collector (50), while after the conversion reaction (e.g., after charging), an alloy or compound (first material (31)) of Li and element X may exist between the solid electrolyte layer (20) and the negative electrode current collector (50). In other words, the secondary battery after the conversion reaction has the same configuration as the secondary battery (101) related to the first form, and the secondary battery before the conversion reaction has the same configuration as the secondary battery (102) related to the second form.

[0134] 4. Method for manufacturing a secondary battery

[0135] The above secondary battery (101, 102) can be manufactured, for example, as follows. That is, as shown in FIG. 4, a method for manufacturing a secondary battery (101, 102) related to one embodiment may include obtaining a laminate (70) having a positive electrode active material layer (10), a solid electrolyte layer (20), a negative electrode current collector (50), and a compound (33) of metal element M and element X disposed between the solid electrolyte layer (20) and the negative electrode current collector (50), and charging the laminate (70) and supplying lithium ions between the solid electrolyte layer (20) and the negative electrode current collector (50) to cause a conversion reaction of the compound (33) of metal element M and element X to produce a first material (31) and a second material (32). Here, the first material (31) is at least one of an alloy of Li and element X, and a compound of Li and element X, and the second material (32) is at least one of a single metal element M, an alloy of Li and metal element M, and a compound of Li and metal element M. Also, as shown in FIG. 4, the laminate (70) may be obtained as follows. That is, the manufacturing method of the present disclosure may include coating the surface of the negative electrode current collector (50) with a compound (33) of metal element M and element X to obtain a coating (60), and stacking the positive electrode current collector (40), the positive electrode active material layer (10), the solid electrolyte layer (20), and the coating (60) to obtain the laminate (70).

[0136] 4.1 Covering

[0137] As shown in FIG. 4, in the manufacturing method related to the present embodiment, the surface of the negative electrode current collector (50) may be coated with a compound (33) of metal element M and element X to obtain a coating (60). As described above, the negative electrode current collector (50) may optionally have a protective layer, etc. The method of coating the surface of the negative electrode current collector (50) with the compound (33) is not particularly limited. For example, the surface of the negative electrode current collector (50) may be coated with the compound (33) by a coating method using a solution or slurry. Alternatively, a transfer material in which a layer made of the compound (33) is formed on a substrate may be obtained, and then the compound (33) may be transferred from the transfer material to the surface of the negative electrode current collector (50). Alternatively, the compound (33) may be coated on the surface of the negative electrode current collector (50) by sputtering, etc. As for the metallic element M or element X, it is as described above. That is, the metallic element M may be Mg. Also, element X may be at least one of Bi, Sb, In, Sn, H, I, Ga, Te, Hg, Cd, Si, B, As, Zn, Ge, Br, P, and Se, and may be at least one of H, B, and P.

[0138] 4.2 Fabrication of Laminates

[0139] As shown in FIG. 4, in the manufacturing method related to the present embodiment, a laminate (70) having a positive electrode active material layer (10), a solid electrolyte layer (20), a compound (33), and a negative electrode current collector (50) in this order may be obtained by using the coating material (60) described above. As shown in FIG. 4, the laminate (70) may also have a positive electrode current collector (40) in contact with the positive electrode active material layer (10). The laminate (70) is easily obtained by molding and laminating each of the materials described above by coating, transferring, bonding, or pressing, etc., so that the positive electrode current collector (40), the positive electrode active material layer (10), the solid electrolyte layer (20), the compound (33), and the negative electrode current collector (50) described above are laminated in this order. The laminate (70) may each include at least one layer of a positive electrode current collector (40), a positive electrode active material layer (10), a solid electrolyte layer (20), a compound (33), and a negative electrode current collector (50). The laminate (70) may have at least one stacked unit of the positive electrode current collector (40), the positive electrode active material layer (10), the solid electrolyte layer (20), the compound (33), and the negative electrode current collector (50) described above, or may have multiple stacked units. In addition, in the laminate (70), multiple stacked units may be electrically connected in series, connected in parallel, or not electrically connected to each other. As is clear from FIGS. 2 and 4, the laminate (70) before charging described later may adopt the same configuration as the secondary battery (102) related to the second form.

[0140] Before or after obtaining the above-mentioned laminate (70), pressure may be applied to each layer or laminate (70) in the thickness direction (stacking direction). For example, each layer constituting the laminate (70) may be pressed to integrate it, or the gaps between each layer constituting the laminate (70) may be eliminated to reduce interfacial resistance. Each layer or laminate (70) may be pressed by known means. For example, each layer or laminate (70) may be pressed in the stacking direction by various pressing methods such as CIP, HIP, roll press, uniaxial press, and die press. The magnitude of the pressure applied to each layer or laminate (70) in the stacking direction may be appropriately determined according to the performance of the intended battery. For example, if each layer or laminate (70) contains a sulfide solid electrolyte, the pressure may be 100 MPa or more, 150 MPa or more, 200 MPa or more, 250 MPa or more, 300 MPa or more, or 350 MPa or more, in order to facilitate the integration or elimination of gaps described above by plastically deforming the sulfide solid electrolyte. The pressurization time or pressurization temperature of each layer or laminate (70) is not particularly limited.

[0141] 4.3 charging

[0142] As shown in FIG. 4, in the manufacturing method related to the present embodiment, charging is performed on the laminate (70) obtained as above, and metallic lithium is deposited between the solid electrolyte layer (20) and the negative electrode current collector (50). Specifically, by charging the laminate (70), lithium ions are conducted from the positive electrode active material included in the positive electrode active material layer (10) to the negative electrode current collector (50) side through the solid electrolyte layer (20), and between the solid electrolyte layer (20) and the negative electrode current collector (50), the lithium ions receive electrons and are deposited as metallic lithium. At this time, a conversion reaction of the compound (33) occurs, and a fresh metal M (second material (32)) is produced together with an alloy or compound of Li and element X (first material (31)), and an alloy or compound of Li and metal element M (second material (32)) may be precipitated starting from the said metal M. Charging may be, for example, the first charge after preparing the laminate (70). The laminate (70) may be charged by the same method as a general battery charging method. That is, charging may be performed by connecting an external power source to the positive electrode current collector (40) and the negative electrode current collector (50) of the laminate (70). As is clear from FIGS. 1 and 4, the laminate (70) after charging described above may adopt the same configuration as the secondary battery (101) related to the first form.

[0143] 4.4 Other processes

[0144] The manufacturing method related to the present embodiment may include general processes for manufacturing a secondary battery in addition to each process described above. For example, a process of housing the laminate (70) inside an outer body such as a laminate film, or a process of connecting a current collection tab to the laminate (70). Specifically, for example, a current collection tab may be connected to the current collector (40, 50) of the laminate (70) (a part of the current collector (40, 50) may be protruded and used as a tab), and then the laminate (70) may be housed inside a laminate film as an outer body, while the tab is pulled out outside the laminate film, the laminate film may be sealed, and then the laminate (70) may be charged by interposing the tab outside the laminate film.

[0145] Additionally, the manufacturing method related to the present embodiment may include selecting a type of compound (33) of metal element M and element X, and when selecting a type of compound (33) of metal element M and element X, it may include confirming that said metal element M and element X satisfy the following relationships (1) and (2). By doing so, a more suitable compound (33) can be efficiently selected. The respective generation energy can be verified, for example, in various databases.

[0146] (1) Energy E of the formation of a compound of metal element M and element X MX a, Formation energy E of the compound of Li and the metal element M LiM Lower than.

[0147] (2) Energy of formation of the compound of Li and element X E LiX a. Formation energy E of a compound of metal element M and element X MX Lower than.

[0148] 5. Vehicles equipped with secondary batteries

[0149] As described above, the secondary battery of the present disclosure can suppress voids, etc. in the negative electrode active material layer, and thus has excellent Coulomb efficiency. Such a secondary battery can be preferably used in at least one type of vehicle selected from, for example, a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and a battery electric vehicle (BEV). That is, the technology of the present disclosure is a vehicle having a secondary battery, wherein the secondary battery comprises the following configuration (A) or (B):

[0150] (A) The above secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and

[0151] The above negative electrode active material layer comprises a first material and a second material, and

[0152] The first material is at least one of an alloy of Li and element X, and a compound of Li and element X, and

[0153] The second material is at least one of the following: a single element of metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M, and also

[0154] The generation energy E of the first substance above LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than ;

[0155] (B) The secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and metallic lithium that is deposited between the solid electrolyte layer and the negative electrode current collector by charging, and

[0156] Between the solid electrolyte layer and the negative electrode current collector, a compound of metal element M and element X exists, and also

[0157] The formation energy E of the compound of the above metal element M and the above element X MX a. Formation energy E of the compound of Li and the above element X LiX Higher than ;

[0158] It also has aspects as such. The details of the composition of the secondary battery are as described above.

[0159] 6. Conditioning method for secondary batteries

[0160] The technology of the present disclosure also has an aspect as a conditioning method for a secondary battery. That is, the conditioning method of the present disclosure comprises preparing a secondary battery having a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and a compound of a metal element M and an element X disposed between the solid electrolyte layer and the negative electrode current collector; and by performing charging of the secondary battery, supplying lithium ions between the solid electrolyte layer and the negative electrode current collector and causing a conversion reaction of the compound of the metal element M and the element X to produce a compound of Li and the element X. By doing so, as described above, the Coulomb efficiency of the secondary battery can be increased.

[0161] Examples

[0162] As described above, although an embodiment of the technology disclosed herein has been explained, the technology disclosed herein may be modified in various ways other than the above embodiment without departing from the gist thereof. The technology disclosed herein will be explained in more detail below with reference to examples, but the technology disclosed herein is not limited to the following examples.

[0163] 1. Production of the entire MgX coat house

[0164] A powder composed of MgX was ground in a mortar for 10 minutes and classified using a 40 μm classifier. Subsequently, 350 mg of mesitylene, 22 mg of a 5 wt% mesitylene solution of styrene-butadiene rubber (SBR), and 200 mg of MgX powder were placed in a container and dispersed using an ultrasonic dispersion device for 30 seconds. Subsequently, the mixture was mixed with a shaker for 3 minutes and further dispersed using an ultrasonic dispersion device for 30 seconds to obtain an MgX slurry. After adhering a Ni foil as a negative electrode current collector to a glass substrate, the MgX slurry was uniformly coated onto the surface of the Ni foil using an applicator to obtain an MgX-coated current collector. The thickness of the MgX layer was 10 μm, and the weight per unit area was 0.2 mg / cm². In this embodiment, one of MgF2, MgB2, Mg3P2, and MgH2 was used as MgX.

[0165] 2. Production of the entire Mg coat house

[0166] Mg was deposited on the surface of a Ni foil, and an Mg-coated current collector (Mg-Ni foil) was obtained. The thickness of the Mg layer was 700 nm.

[0167] 3. Preparation of the entire Mikot house

[0168] A Ni foil that was not coated with MgX or Mg was prepared.

[0169] 4. Production of evaluation cells

[0170] As shown in FIG. 5, an evaluation cell was obtained by stacking a Li metal layer, a solid electrolyte layer, and the current collector. Specifically, 101.7 mg of a sulfide-based solid electrolyte (a Li2S-P2S5-based material containing LiBr and LiI) was prepared and press-molded at a pressure of 1 ton / cm² to obtain a solid electrolyte layer. Next, a negative electrode current collector was installed at the bottom of the solid electrolyte layer and press-molded at a pressure of 1 ton / cm² to obtain a laminate of the solid electrolyte layer and the negative electrode current collector. In addition, a Li foil was installed on the top of the solid electrolyte layer of the laminate and press-molded, and subsequently, an evaluation cell was obtained by constraining it at 2 N·m.

[0171] 4.1 Comparative Example 1

[0172] An evaluation cell was prepared as described above using a Micot current collector (Ni foil).

[0173] 4.2 Comparative Example 2

[0174] An evaluation cell was fabricated as described above using an Mg-coated current collector (Mg-coated Ni foil).

[0175] 4.3 Comparative Example 3

[0176] An evaluation cell was fabricated as described above using an MgF2 coated current collector (MgF2 coated Ni foil) as the MgX coated current collector.

[0177] 4.4 Example 1

[0178] An evaluation cell was fabricated as described above using an MgB2 coated current collector (MgB2 coated Ni foil) as the MgX coated current collector.

[0179] 4.5 Example 2

[0180] An evaluation cell was fabricated as described above using an Mg3P2 coated current collector (Mg3P2 coated Ni foil) as the MgX coated current collector.

[0181] 4.6 Example 3

[0182] An evaluation cell was fabricated as described above using an MgH2 coated current collector (MgH2 coated Ni foil) as the MgX coated current collector.

[0183] 5. Evaluation of Coulomb Efficiency

[0184] The evaluation cell was placed in a constant temperature bath at 60 ℃ for 3 hours to equalize the cell temperature. Next, the evaluation cell was charged with a constant current of 435 μA / cm² to precipitate Li, and charging was stopped when the charge capacity reached 4.35 mAh / cm². After 10 minutes, the cell was discharged with a constant current of 435 μA / cm² to dissolve Li, and discharge was terminated when 1.0 V was reached. The Coulomb efficiency of each evaluation cell was calculated from the following equation.

[0185] (Coulomb efficiency [%)) = [(Discharge capacity) / (Charge capacity)] × 100

[0186] = [(Capacity at 1.0 V [mAh / ㎠]) / 4.35 [mAh / ㎠]] × 100

[0187] 6. Calculation of Generation Energy

[0188] Referencing the generation energy in the Material Project database, the generation energy of MgX (E MX [eV / atom]) and the generation energy of LiX (E LiX Calculate [eV / atom]) and the difference (ΔE = E MX - E LiX ) obtained.

[0189] 7. Measurement of Precipitation Overpotential (Nucleation Overpotential)

[0190] For each evaluation cell, the nucleation overpotential was measured by reading the maximum voltage when Li was deposited up to a capacity of 1 mAh. The nucleation overpotential of the first charge-discharge cycle and the nucleation overpotential of the second cycle were calculated, respectively.

[0191] 8. Observation of cell cross-section before and after charging and discharging

[0192] (1) A fracture surface of the evaluation cell before charging was obtained.

[0193] (2) A fracture surface was obtained after precipitating Li by charging with a constant current of 490 μA / ㎠ for 5 hours.

[0194] (3) Cross-sectional observation was performed using SEM-EDX on each of the fracture surfaces of (1) and (2) above.

[0195] 9. Evaluation Results

[0196] 9.1 On Coulomb Efficiency and Energy Generated

[0197] Table 1 and Figure 6 below show the Coulomb efficiency [%] of each evaluated cell. Also, in Table 1 below, the generation energy of MgX (E MX [eV / atom]) and the generation energy of LiX (E LiX [eV / atom]) and its difference (ΔE = E MX - E LiX It represents ).

[0198]

[0199] As shown in Table 1 and Figure 6, Examples 1 to 3, where ΔE is a positive value, showed improved Coulomb efficiency compared to Comparative Examples 1 and 2, which do not contain MgX, and Comparative Example 3, where ΔE is a negative value. When ΔE is a positive value, it is believed that during the charging of the evaluation cell, a conversion reaction of MgX occurs, generating LiX and fresh Mg. In Examples 1 to 3, due to this fresh Mg, metallic lithium (Li-Mg alloy) is uniformly deposited between the solid electrolyte layer and the negative electrode current collector, thereby suppressing the occurrence of voids. Additionally, metallic lithium is uniformly deposited near the surface of the solid electrolyte layer, resulting in a good interface between the solid electrolyte layer and metallic lithium. Furthermore, it is believed that lithium ion conductivity is secured through LiX from the conversion reaction, thereby improving Coulomb efficiency.

[0200] In addition, it is believed that Comparative Example 1, which does not contain Mg or MgX, had a significantly reduced Coulomb efficiency because metallic lithium was unevenly deposited between the solid electrolyte layer and the negative electrode current collector. Also, it is believed that Comparative Example 2, which contains Mg, had improved Coulomb efficiency because the presence of Mg between the solid electrolyte layer and the negative electrode current collector allowed for the uniform deposition of a Li-Mg alloy as metallic lithium between the solid electrolyte layer and the negative electrode current collector during charging. Furthermore, Comparative Example 3, in which ΔE is a negative value, had a higher Coulomb efficiency than Comparative Example 1, which does not contain Mg or MgX, but a lower Coulomb efficiency than Comparative Example 2, which contains Mg. In Comparative Example 3, it is believed that the conversion reaction of MgX did not proceed, and MgX, which is disadvantageous to the battery reaction, remained present even after charging.

[0201] 9.2 On Nucleation Overpotential (Precipitation Overpotential)

[0202] Table 2 below shows the results of the nucleation overpotential (precipitation overpotential) of each evaluation cell.

[0203]

[0204] As shown in Table 2, Comparative Example 2 has a lower precipitation overpotential than Comparative Example 1. Here, a low precipitation overpotential means that the energy barrier for precipitating metallic lithium is small, and a lower precipitation overpotential makes it easier for metallic lithium to precipitate uniformly and increases Coulomb efficiency. From Comparative Example 2, it can be seen that the precipitation overpotential can be suppressed to a low level through the alloying reaction of Mg and Li. In particular, the precipitation overpotential tends to become even smaller after the second cycle, when the battery reaction stabilizes. Meanwhile, for Examples 1 to 3, similar to Comparative Example 2, the precipitation overpotential was significantly reduced after the second cycle. In Examples 1 to 3, it is believed that the conversion of MgX proceeded during the first cycle, generating fresh Mg element, and after the second cycle, metallic lithium was uniformly precipitated starting from this Mg element. In short, just as with the results of the generation energy difference ΔE shown in Table 1, it can be said from the results of Table 2 that the conversion reaction proceeded in Examples 1 to 3. Furthermore, as shown in Table 2, for Comparative Example 3 as well, the precipitation overpotential after the second cycle decreased slightly, but the precipitation overpotential remained high. Also, as shown in Table 1, the generation energy difference ΔE is small. Therefore, it is thought that the conversion reaction did not proceed in Comparative Example 3.

[0205] 9.3 SEM / EDX before and after Li precipitation

[0206] For each of the evaluation cells related to Comparative Example 3 and the evaluation cells related to Example 3, the cell cross-sections before and after Li precipitation were observed and evaluated using SEM / EDX. Figure 7 is the result for Comparative Example 3, and Figures 8 and 9 are the result for Example 3.

[0207] As shown in FIG. 7, in Comparative Example 3, there is no substantial change in the distribution of Mg in the cell cross-section before and after charging. In addition, no diffusion of Mg is observed in the metallic lithium precipitated after charging. That is, in Comparative Example 3, it can be seen that the conversion reaction of MgF2 does not proceed during charging.

[0208] As shown in Fig. 8, in Example 3, the distribution of Mg in the cell cross-section changes significantly before and after charging. Specifically, it can be seen that Mg is diffused into the metallic lithium precipitated after charging. That is, in Example 3, it can be seen that the conversion reaction of MgH2 proceeds during charging, fresh Mg is generated, and this serves as a starting point for the precipitation of metallic lithium, resulting in the precipitation of a Li-Mg alloy.

[0209] As shown in FIG. 9, in Example 3, there is a region between the region where S is present (corresponding to the solid electrolyte layer) and the region where Ni is present (corresponding to the negative electrode current collector) where Ni, Mg, and S are all absent, and it is believed that LiH generated by the conversion reaction exists in this region. In Examples 1 and 2 as well, similar to Example 3, it is believed that a conversion reaction occurs during charging, and a Li-Mg alloy is precipitated starting from fresh Mg. From FIG. 9, it can be said that LiH exists as a film, and its thickness is 10 nm or more and 50 μm or less.

[0210] 10. Further Review

[0211] 10.1 Energy difference between LiX and MX and energy difference between LiM and MX

[0212] Formation energy (E) of Li and Mg alloy (Li-Mg) LiM ) is -0.061 [eV / atom]. The E in question LiM and E shown in Table 1 aboveLiX and E shown in Table 1 above MX By comparing, it can be seen that the metal element M (Mg) and element X used in Examples 1 to 3 satisfy the following relationships (1) and (2).

[0213] (1) Energy E of the formation of the compound of the metal element M and the element X MX a, Formation energy E of the compound of Li and the metal element M LiM Lower than.

[0214] (2) Energy of formation of the compound of Li and element X E LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than.

[0215] 10.2 CV Measurement

[0216] CV measurements were performed on the evaluation cell related to Example 3 above under the following conditions. The results are shown in FIG. 10.

[0217] Measurement conditions: 1 mV / s, -0.04 V ~ 3 V, 60 ℃

[0218] As shown in Fig. 10, a redox peak originating from the conversion reaction of MgH2 was observed around 0.5 V. In addition, it was confirmed that the evaluation cell operated reversibly even after 80 cycles.

[0219] 10.3 XRD Measurement

[0220] For the evaluation cell related to Example 3 above, after charging (Li deposition) for 6 hours with a constant current of 490 μA / cm², the cell was disassembled, and XRD measurements were performed targeting the interface between the solid electrolyte layer and the deposited Li. The XRD measurement conditions are as follows. The results are shown in Fig. 11.

[0221] Scan speed: 5° / min

[0222] Scan range: 5 - 90°

[0223] Step width: 0.02°

[0224] As shown in Fig. 11, in the evaluation cell after charging, it was found that MgH2 is substantially absent at the interface between the solid electrolyte layer and the precipitated Li, while the solid electrolyte, Li-Mg, and LiH coexist.

[0225] 10.4 When the position of MgX is changed (Example 4)

[0226] An evaluation cell having the configuration shown in Fig. 5 was obtained by laminating a solid electrolyte layer transferred with a Li metal layer and MgH2, and a Micort current collector. Specifically, 101.7 mg of a sulfide-based solid electrolyte (a Li2S-P2S5-based material containing LiBr and LiI) was prepared and press-molded at a pressure of 1 ton / cm² to obtain a solid electrolyte layer. Next, a layer composed of MgH2 was laminated onto the surface of the solid electrolyte layer, and then press-molded at a pressure of 2 ton / cm² to transfer a layer composed of MgH2 onto the surface of the solid electrolyte layer. Next, a negative electrode current collector was installed below the MgH2 layer and press-molded at a pressure of 6 ton / cm² to obtain a laminate of the solid electrolyte layer, the MgH2 layer, and the negative electrode current collector. In addition, a Li foil was installed on the upper part of the solid electrolyte layer of the laminate and press molding was performed, and then, by constraining it with 2 N·m, an evaluation cell related to Example 4 was obtained.

[0227] For the obtained evaluation cell, a fracture surface was obtained after precipitating Li by charging it with a constant current of 490 μA / cm² for 5 hours, and then cross-sectional observation was performed using SEM-EDX. The results are shown in Fig. 12. As shown in Fig. 12, it was confirmed that LiH is present at the interface between the solid electrolyte layer and the Li-Mg layer. In addition, the Coulomb efficiency was measured for the evaluation cell in the same manner as above, and a Coulomb efficiency of the same magnitude as that of Example 3 was obtained. From these results, it is believed that there is no particular limitation on the location of LiX (LiH) in the negative electrode active material layer.

[0228] Regarding the types of 10.5 MgX

[0229] In the above, H, B, and P were exemplified as element X, but element X is not limited to these. By referring to the generation energy in the Material Project database, elements other than H, B, and P applicable as element X were extracted. Examples of the above ΔE being a defined value are shown in Table 3 below. For reference, ΔE when element X is H, B, and P is also listed. It is believed that when the elements exemplified below are adopted as element X, the same effect as in Examples 1 to 3 is produced.

[0230]

[0231] 11. Supplement and Conclusion

[0232] In the above examples, specific compounds of metal element M and element X were exemplified, but it is believed that the same effect is exhibited as long as MX is capable of causing the conversion reaction. That is, the metal element M is not limited to Mg. However, it is believed that when the metal element M is Mg, the precipitation of metallic lithium during charging is more likely to be more uniform. Also, the element X is not limited to those exemplified above. However, it is believed that when element X is at least one of H, B, and P, the LiX after the conversion reaction has high lithium ion conductivity, etc. Furthermore, as described above, when the metal element is Mg, it is believed that an excellent effect is exhibited when element X is at least one of Bi, Sb, In, Sn, H, I, Ga, Te, Hg, Cd, Si, B, As, Zn, Ge, Br, P, and Se.

[0233] In the above example, an evaluation cell shown in FIG. 5 was fabricated to simply evaluate the precipitation behavior and Coulomb efficiency of metallic lithium, but when constructing an actual secondary battery, it can be replaced with a Li foil and a suitable configuration can be adopted as the positive electrode.

[0234] In the above embodiment, a specific sulfide solid electrolyte was used in the solid electrolyte layer as an example, but the type of solid electrolyte included in the solid electrolyte layer is not limited to this. However, when a sulfide solid electrolyte is included in the solid electrolyte layer, it is easier to obtain higher performance as a secondary battery.

[0235] In the above embodiment, the case in which Ni foil is used as the negative electrode current collector was exemplified, but the composition of the negative electrode current collector is not limited to this. However, it is believed that if a negative electrode current collector comprising at least one of Ni and stainless steel is used, the alloying reaction between the negative electrode current collector and lithium can be suppressed.

[0236] As described above, a secondary battery having the following configuration can be said to have excellent Coulomb efficiency while having a precipitation-type metal lithium negative electrode. That is, the secondary battery of the present disclosure has the following configuration (A) or (B).

[0237] (A) The above secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, and

[0238] The above negative electrode active material layer comprises a first material and a second material, and

[0239] The first material is at least one of an alloy of Li and element X, and a compound of Li and element X, and

[0240] The second material is at least one of the following: a single element of metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M, and also

[0241] The generation energy E of the first substance above LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than.

[0242] (B) The secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and metallic lithium that is deposited between the solid electrolyte layer and the negative electrode current collector by charging, and

[0243] Between the solid electrolyte layer and the negative electrode current collector, a compound of metal element M and element X exists, and also

[0244] The formation energy E of the compound of the above metal element M and the above element X MX a. Formation energy E of the compound of Li and the above element X LiX It is higher than. Explanation of the symbols

[0245] 10: Positive electrode active material layer 20: Solid electrolyte layer 30: Negative electrode active material layer 31: First substance 32: Second substance 33: Compounds of metallic element M and element X 40 : Entire house of a serious play 50 : Bu-geuk entire house 60 : Covering 70 : Laminate 101, 102: Secondary battery

Claims

Claim 1 A secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer, wherein the solid electrolyte layer comprises a sulfide solid electrolyte, and the negative electrode active material layer comprises a first material and a second material, wherein the first material is at least one of an alloy of Li and element X and a compound of Li and said element X, and said element X is at least one of B and P, and the second material is at least one of a single metal element M, an alloy of Li and said metal element M, and a compound of Li and said metal element M, and said metal element M is Mg, and furthermore, the generation energy E of the first material LiX a, formation energy E of the compound of the metal element M and the element X MX Lower, secondary battery. Claim 2 A secondary battery according to claim 1, wherein the negative electrode active material layer comprises the first material formed as a film, and the thickness of the first material formed as a film is 10 nm or more and 50 μm or less. Claim 3 A secondary battery comprises a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and metallic lithium precipitated between the solid electrolyte layer and the negative electrode current collector by charging, wherein the solid electrolyte layer comprises a sulfide solid electrolyte, and a compound of a metal element M and an element X exists between the solid electrolyte layer and the negative electrode current collector, wherein the metal element M is Mg and the element X is at least one of B and P, and furthermore, the formation energy E of the compound of the metal element M and the element X MX a. Formation energy E of the compound of Li and the above element X LiX Higher, secondary battery. Claim 4 A secondary battery according to claim 3, configured such that during charging, a compound of the metal element M and the element X decomposes to form a compound of the Li and the element X on the surface of the negative electrode current collector. Claim 5 A secondary battery according to any one of claims 1 to 4, wherein the metal element M and the element X satisfy the following relationships (1) and (2): (1) the energy E of the formation of a compound of the metal element M and the element X. MX a, Formation energy E of the compound of Li and the metal element M LiM Lower than, and also (2) the formation energy E of the compound of Li and the element X. LiX a, formation energy E of the compound of the metal element M and the element X MX Lower than Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 In any one of claims 1 to 4, the generated energy E MX and the above generation energy E LiX A secondary battery with a difference of 0.027 eV / atom or greater. Claim 10 A method for manufacturing a secondary battery comprises obtaining a laminate having a positive electrode active material layer, a solid electrolyte layer, a negative electrode current collector, and a compound of a metal element M and an element X disposed between the solid electrolyte layer and the negative electrode current collector; and charging the laminate to supply lithium ions between the solid electrolyte layer and the negative electrode current collector and causing a conversion reaction of the compound of the metal element M and the element X to produce a first material and a second material, wherein the solid electrolyte layer comprises a sulfide solid electrolyte, the first material is at least one of an alloy of Li and element X and a compound of Li and element X, and the element X is at least one of B and P, the second material is at least one of a single metal element M, an alloy of Li and the metal element M, and a compound of Li and the metal element M, and the metal element M is Mg, and the generation energy E of the first material LiX a, formation energy E of the compound of the metal element M and the element X MX Lower manufacturing method.

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