Lithium secondary battery and method for producing a lithium secondary battery

Abstract

An object of the present disclosure is to provide a lithium secondary battery capable of improving cycle characteristics while increasing reversible capacity. A lithium secondary battery is described that includes a negative electrode current collector layer, a first lithium-tin alloy layer, a lithium-magnesium alloy layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in the order mentioned.

Description

AREA

[0001] The present disclosure relates to a lithium secondary battery and a method for manufacturing a lithium secondary battery. BACKGROUND

[0002] Lithium secondary batteries use a lithium metal and / or a lithium alloy as the negative electrode active material, which exhibits a high ionization tendency among metals. Such lithium secondary batteries are expected to be used in practice because they not only have a large potential difference between a negative and a positive electrode, thus providing a high output voltage, but also have a high theoretical capacity density.

[0003] For example, PTL 1 discloses an all-solid-state battery using a precipitation-dissolution reaction of metallic lithium as a negative electrode reaction, including a positive electrode having a positive electrode layer; a negative electrode having a negative electrode current collector and a negative electrode layer; and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer. This all-solid-state battery is characterized in that the negative electrode layer contains a β-single-phase alloy of metallic lithium and metallic magnesium as a negative electrode active material; and that, when the all-solid-state battery is fully charged, the ratio of the lithium element in the alloy is 81.80 atomic % to 99.97 atomic %. According to PTL 1, an all-solid-state battery with high charge-discharge efficiency can be provided.

[0004] PTL 2 discloses an all-solid-state battery including: a positive electrode layer containing a positive electrode active material layer; a negative electrode active material layer; and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer and containing a solid electrolyte.In this all-solid-state battery, the negative electrode layer includes a negative electrode current collector, a first negative electrode active material layer in contact with the solid electrolyte layer, and a second negative electrode active material layer disposed between the negative electrode current collector and the first negative electrode active material layer; the first negative electrode active material layer includes a first carbonaceous negative electrode active material; the second negative electrode active material layer includes a second carbonaceous negative electrode active material; and an intensity ratio (I. 1 D / I 1 G ) of a D-band peak and a G-band peak in a Raman spectrum of the first carbonaceous negative electrode active material is lower than an intensity ratio (I 2 D / I 2 G) of the second carbonaceous negative electrode active material. According to PTL 2, an all-solid-state battery with excellent cycling characteristics and short circuit prevention can be provided. CITATION LISTPATENT LITERATURE [PTL 1] Unexamined Japanese Patent Publication (Kokai) No. 2020-184513 [PTL 2] Unexamined Japanese Patent Publication (Kokai) No. 2021-132033 SHORT DISPLAY TECHNICAL PROBLEM

[0005] Lithium secondary batteries are expected to have excellent battery performance; however, in reality, lithium secondary batteries have low reversible capacity and are still inadequate in terms of cycle performance. Therefore, lithium secondary batteries have room for improvement in terms of reversible capacity and cycle performance.

[0006] In view of the above, an object of the present disclosure is to provide a lithium secondary battery in which cycle characteristics can be improved while increasing the reversible capacity. SOLUTION TO THE PROBLEM

[0007] The present disclosure achieves the above-described object by the following means. <Gesichtspunkt 1>

[0008] A lithium secondary battery comprising a negative electrode current collector layer, a first lithium-tin alloy layer, a lithium-magnesium alloy layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in the order mentioned. <Gesichtspunkt 2>

[0009] The lithium secondary battery according to aspect 1, wherein the first lithium-tin alloy layer has a thickness of 0.1 to 15 µm in a fully charged state. <Gesichtspunkt 3>

[0010] The lithium secondary battery according to aspect 1 or 2, wherein the lithium-magnesium alloy layer has a thickness of 0.1 to 40 µm in a fully charged state. <Gesichtspunkt 4>

[0011] The lithium secondary battery according to any one of aspects 1 to 3, comprising the negative electrode current collector layer, the first lithium-tin alloy layer, the lithium-magnesium alloy layer, a second lithium-tin alloy layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector layer in the order mentioned. <Gesichtspunkt 5>

[0012] The lithium secondary battery according to any one of aspects 1 to 4, wherein in a fully charged state, the first lithium-tin alloy layer has a thickness of 0.1 to 15 µm, and the second lithium-tin alloy layer has a thickness of 0.1 to 15 µm. <Gesichtspunkt 6>

[0013] A method of manufacturing the lithium secondary battery according to any one of aspects 1 to 5, the method comprising the following steps: Obtaining a preliminary lithium secondary battery by laminating the negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, the electrolyte layer, the positive electrode active material layer that retains lithium, and the positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-tin alloy layer; and (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer. <Gesichtspunkt 7>

[0014] A method of manufacturing the lithium secondary battery according to any one of aspects 1 to 5, the method comprising the following steps: Obtaining the preliminary lithium secondary battery by laminating the negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, a tin-containing third metal layer, the electrolyte layer, the positive electrode current collector layer that retains the lithium, and the positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the first lithium-tin alloy layer; (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer; and (iii) allow tin of the third metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the second lithium-tin alloy layer. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0015] According to the present lithium secondary battery, the cycle characteristics can be improved while increasing the reversible capacity. BRIEF DESCRIPTION OF THE DRAWINGS Fig.1 is a schematic drawing illustrating the lithium secondary battery of the present disclosure. Fig. 2 is a schematic drawing illustrating another aspect of the lithium secondary battery of the present disclosure. Fig. 3 is a schematic drawing illustrating a method for manufacturing the lithium secondary battery according to the present disclosure. Fig. 4 is a schematic drawing illustrating another aspect of a method for manufacturing the lithium secondary battery of the present disclosure. Fig. Figure 5 provides images showing the results of EDX mapping analysis by SEM-EDX cross-section for each element with respect to a lithium secondary battery E2 of Example 2 ( Fig. 5A: a superposition of the elements sulfur (S), oxygen (O), tin (Sn), magnesium (Mg) and nickel (Ni); Fig. 5B: S; Fig. 5C: O; Fig. 5D: Sn; Fig. 5E: Mg; and Fig. 5F: Ni). Fig. 6 provides SEM cross-sectional images of the lithium secondary battery E2 of Example 2 ( Fig. 6A is a SEM cross-sectional image, and Fig. 6B is a schematic drawing of a cross-sectional structure). DESCRIPTION OF THE EMBODIMENTS

[0016] Embodiments of the present disclosure will now be described in detail. However, the present disclosure is not limited to the embodiments described below and may be embodied with various modifications within the scope of the present disclosure. In the descriptions of the drawings, the same symbol is used for the same element, and redundant descriptions are omitted.

[0017] For the purposes of the present disclosure, the term "mixture" means a composition that can form a positive electrode active material layer or an electrolyte layer alone or with other components. Furthermore, the term "mixture slurry" for the purposes of the present disclosure means a slurry that contains a dispersant in addition to a "mixture," and thus can be applied and dried to form a positive electrode active material layer or an electrolyte layer.

[0018] The lithium secondary battery of the present disclosure may be a liquid battery containing an electrolyte solution as the electrolyte layer, or it may be a solid-state battery including a solid electrolyte layer as the electrolyte layer. In the present disclosure, the term "solid-state battery" means a battery in which at least one solid electrolyte is used as the electrolyte, and accordingly, a solid-state battery may include a combination of a solid electrolyte and a liquid electrolyte as the electrolyte. Further, the lithium secondary battery of the present disclosure may be an all-solid-state battery, that is, a battery in which only a solid electrolyte is used as the electrolyte. <<Lithium-Sekundärbatterie> >

[0019] The lithium secondary battery of the present disclosure includes a negative electrode current collector layer, a first lithium-tin alloy layer, a lithium-magnesium alloy layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in the order mentioned.

[0020] According to the present lithium secondary battery, the cycle characteristics can be improved while increasing the reversible capacity.

[0021] As in Fig.1, the lithium secondary battery of the present disclosure includes a first lithium-tin alloy layer 120 between a negative electrode current collector layer 110 and a lithium-magnesium alloy layer 121. It is believed that the first lithium-tin alloy layer 120 prevents interfacial delamination between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121 during discharge, thereby improving cycle characteristics while increasing reversible capacity.

[0022] The following is considered to be a factor that enables the first lithium-tin alloy layer 120 to prevent interfacial delamination between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121, although the details thereof are unclear. During discharge, from the standpoint of reaction potential, the dealloyation of lithium contained in the lithium-tin alloy layer 121 proceeds preferentially to the dealloyation of lithium contained in the first lithium-tin alloy layer 120; therefore, the lithium-tin alloy layer 121 contracts greatly.On the other hand, dealloying reaction of the first lithium-tin alloy layer 120 is less likely than that of the lithium-magnesium alloy layer 121, and the first lithium-tin alloy layer 120 therefore contracts less than the lithium-magnesium alloy layer 121; therefore, the contraction of the lithium-magnesium alloy layer 121 is relaxed by the first lithium-tin alloy layer 120, and it is believed that the above-described interfacial delamination can be prevented as a result. <negativelektrodenstromabnehmerschicht>

[0023] The material used in the negative electrode current collector layer is not particularly limited, and any material generally used as a negative electrode current collector of a lithium secondary battery can be adopted. Examples of the material used in the negative electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, steel sheet, and carbon. In particular, from the viewpoint of ensuring reduction resistance and making it difficult to alloy with lithium, the material used in the negative electrode current collector layer may contain at least one metal selected from Cu, Ni, and stainless steel, or may be made of a carbon sheet. The negative electrode current collector layer may have some kind of coating on its surface for, for example, adjusting resistance.

[0024] The shape of the negative electrode current collector layer is not particularly limited, and examples include a foil shape, a plate shape, and a mesh shape. A foil shape is preferred.

[0025] The thickness of the negative electrode current collector layer is not particularly limited and may be 0.1 μm or more, or 1 μm or more but 1 mm or less, or 100 μm or less. <Erste Lithium-Zinn-Legierungsschicht>

[0026] The first lithium-tin alloy layer contains a lithium element and a tin element, and may optionally also contain other metal elements that form an alloy with lithium. It is believed that the first and second lithium-tin alloy layers also function as a negative electrode active material layer in the lithium secondary battery of the present disclosure, depending on the charge / discharge state.

[0027] The thickness of the first lithium-tin alloy layer is not particularly limited and may be 0.1 to 15 μm in a fully charged state. The thickness of the first lithium-tin alloy layer may be 0.1 μm or more, 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1.0 μm or more but 15 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less, but is not particularly limited.

[0028] Regarding a method for producing the first lithium-tin alloy layer, reference may be made to the “<<Verfahren zum Herstellen einer Lithium-Sekundärbatterie> >". <lithium-magnesium-legierungsschicht>

[0029] The lithium-magnesium alloy layer contains a lithium element and a magnesium element, and may optionally also contain other metal elements that form an alloy with lithium. In the lithium secondary battery of the present disclosure, this lithium-magnesium alloy layer functions as a negative electrode active material layer.

[0030] The thickness of the lithium-magnesium alloy layer is not particularly limited and can be 0.1 to 40 μm in a fully charged state. The thickness of the lithium-magnesium alloy layer can be 0.1 μm or more, 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1.0 μm or more but 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less, but is not particularly limited.

[0031] Regarding a method for producing the lithium-magnesium alloy layer, reference can be made to the “<<Verfahren zum Herstellen einer Lithium-Sekundärbatterie> >". < Electrolyte layer><Elektrolytschicht - Festelektrolytschicht>

[0032] The lithium secondary battery of the present disclosure may be an all-solid-state battery, that is, it may include a solid electrolyte layer as an electrolyte layer.

[0033] If necessary, the solid electrolyte layer may contain a binder and the like in addition to a solid electrolyte. (solid electrolyte)

[0034] The material of the solid electrolyte is not particularly limited and can be, for example, a sulfide solid electrolyte, an oxide solid electrolyte or a polymer electrolyte.

[0035] Examples of sulfide solid electrolytes include, but are not limited to: sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include, but are not limited to: Li 2 SP 2 S 5 -based electrolytes (e.g. Li 7 P 3 S 11 , Li 3 PS 4 and Li 8 P 2 S 9 ), Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 SP 2 S 5 , LiI-LiBr-Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -GeS 2 (e.g. Li 13 GeP 3 S 16 and Li 10 GeP 2 S 12 ), LiI-Li 2 SP 2 O 5 , LiI-Li 3 PO 4 -P 2 S 5 and Li 7-x PS 6-x Cl x ; and combinations thereof.

[0036] Examples of oxide solid electrolytes include, but are not limited to, Li 7 La 3 Zr 2 O 12 , Li 7-x La 3 Zr 1-x Nb x O 12 , Li 7-3x La 3 Zr 2 Al x O 12 , Li 3x La 2 / 3-x TiO 3 , Li 1+x Al x Ti 2-x (PO 4 ) 3 , Li 1+x Al x Ge 2-x (PO 4 ) 3 , Li 3 PO 4 , and Li 3+x PO 4-x N x (LiPON).

[0037] The sulfide solid electrolyte and the oxide solid electrolyte can each be a glass or a crystallized glass (glass ceramic).

[0038] Examples of polymer electrolytes include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO), and their copolymers. (Binder)

[0039] The binder is not particularly limited. The binder may be, for example, but not exclusively, polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), or styrene-butadiene rubber (SBR). The binder is not particularly limited and can be used singly or in combination with two or more of them.

[0040] The thickness of the solid electrolyte layer is not particularly limited and may be, for example, 0.1 µm or more, 1 µm or more, or 10 µm or more but 2 mm or less, 1 mm or less, or 500 µm or less.

[0041] The solid electrolyte layer can be easily formed, for example, by dry or wet forming an electrolyte mixture containing the above-described solid electrolyte, binder, and the like. <Elektrolytschicht - Separatorschicht>

[0042] The lithium secondary battery of the present disclosure may be a liquid battery, that is, it may include an electrolyte solution, particularly an electrolyte solution retained in a separator layer, as an electrolyte layer. (electrolyte solution)

[0043] The electrolyte solution is not particularly limited and preferably contains a carrier salt and a solvent.

[0044] The carrier salt (lithium salt) of the electrolyte solution with lithium ion conductivity is not particularly limited and can be, for example, an inorganic lithium salt or an organic lithium salt. Examples of the inorganic lithium salt include LiPF. 6 , LiBF 4 , LiClO 4 , and LiAsF 6 Examples of organic lithium salts include, but are not limited to, LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , LiN(FSO 2 ) 2 and LiC(CF 3 SO 2 ) 3 .

[0045] The solute used in the electrolyte solution is not particularly limited and can be, for example, a cyclic carbonate or a chain carbonate. Examples of cyclic carbonates include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Examples of chain carbonates include, but are not limited to, dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The electrolyte solution is not particularly limited and can be used alone or in combination with two or more types of them. (Separator)

[0046] The separator is not particularly limited, and any separator generally used as a separator for a lithium secondary battery can be considered suitable. For example, a polyolefin-, polyamide-, or polyimide-based nonwoven fabric can be used as the separator. <positivelektrodenaktivmaterialschicht>

[0047] The positive electrode active material layer contains at least one positive electrode active material and may further contain a conductive auxiliary agent, a solid electrolyte, a binder, and the like. Furthermore, the positive electrode active material layer may further contain various additives. In the positive electrode active material layer, the content of the positive electrode active material, the conductive auxiliary agent, the binder, and the like can be determined depending on the target battery performance. For example, assuming the total amount (all solids) of the positive electrode active material layer to be 100 mass%, the content of the positive electrode active material may be 40 mass% or more, 50 mass% or more, 60 mass% or more, but 100 mass% or less, or 90 mass% or less. (Positive electrode active material)

[0048] The positive electrode active material is not particularly limited as long as it is capable of enclosing and releasing lithium ions. The positive electrode active material can be, for example, but not limited to, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMn O 24 ), nickel cobalt lithium manganate (NCM), LiCO 1 / 3 No 1 / 3 Mn 1 / 3 O 2 , nickel cobalt lithium aluminate (NCA; LiNi x Co y Al z O 2 ), or a heteroelement-substituted Li-Mn spinel with a composition represented by Li 1+x Mn 2-×-y M y O 4 (where M represents at least one metal element selected from the group consisting of Al, Mg, Co, Fe, Ni and Zn).

[0049] The positive electrode active material is not particularly limited and may include a coating layer. The coating layer is a layer containing a substance that exhibits lithium ion conductivity, has low reactivity with the positive electrode active material or the solid electrolyte, and can maintain a coating layer shape that is not liquefied even when it comes into contact with the active material or the solid electrolyte. Specific examples of a material constituting the coating layer include LiNbO, among others. 3 , Li 4 Ti 5 O 12 and Li 3 PO 4 .

[0050] The shape of the positive electrode active material is not particularly limited, as long as it is a shape common to positive electrode active materials of lithium secondary batteries. For example, the positive electrode active material may be in the form of particles. The positive electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The positive electrode active material may have an average particle size D 50 of, for example, 1 nm or more, 5 nm or more, or 10 nm or more but 500 µm or less, 100 µm or less, 50 µm or less, or 30 µm or less. The average particle size D 50 is a particle size (mean diameter) at a cumulative value of 50% in a volume-based particle size distribution determined by a laser diffraction scattering method. (Conductive aid)

[0051] The conductive aid is not particularly limited. Examples of the conductive aid include, but are not limited to, vapor-grown carbon fibers (VGCFs), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNTs), and carbon nanofibers (CNFs). The conductive aid can be in the form of particles or fibers, for example, and the size of the aid is not particularly limited. The conductive aid is not particularly limited and can be used alone or in combination with two or more types.

[0052] Regarding the solid electrolyte and the binder, the above-described “<Elektrolytschicht - Festelektrolytschicht> " are referred to.

[0053] The shape of the positive electrode active material layer is not particularly limited, and the positive electrode active material layer may, for example, be in the form of a sheet with a substantially flat surface. The thickness of the positive electrode active material layer is also not particularly limited and may, for example, be 0.1 μm or more, 1 μm or more, 10 μm or more but 2 mm or less, 1 mm or less, or 500 μm or less. <positivelektrodenstromabnehmerschicht>

[0054] The material used in the positive electrode current collector layer is not particularly limited, and any material generally used as a positive electrode current collector of a lithium secondary battery can be adopted. Examples of the material used in the positive electrode current collector layer include, but are not limited to, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. The positive electrode current collector layer may have some kind of coating on its surface for, for example, adjusting the resistance. Further, the positive electrode current collector layer may be a metal foil or a substrate on which any of the metals described above is evaporated or deposited.

[0055] The shape of the positive electrode current collector layer is not particularly limited, and examples include a foil shape, a plate shape, and a mesh shape. A foil shape is preferred.

[0056] The thickness of the positive electrode current collector layer is not particularly limited and may be 0.1 µm or more, or 1 µm or more but 1 mm or less, or 100 µm or less.

[0057] The positive electrode active material layer can be prepared by any known method. For example, the positive electrode active material layer can be easily formed by dry or wet casting a positive electrode mixture containing the various components described above. The positive electrode active material layer can be formed together with the positive electrode current collector layer or formed separately from the positive electrode current collector layer.

[0058] Examples of the shape of the lithium secondary battery include, but are not limited to, a coin shape, a laminated shape (pocket battery), a cylindrical shape, and a prismatic shape.

[0059] Fig. 1 is a schematic drawing illustrating one aspect of the lithium secondary battery of the present disclosure; however, the lithium secondary battery of the present disclosure is not limited to this case.

[0060] A lithium secondary battery 100 is a battery in which a negative electrode current collector layer 110, a first lithium-tin alloy layer 120, a lithium-magnesium alloy layer 121, an electrolyte layer 130, a positive electrode active material layer 140, and a positive electrode current collector layer 150 are laminated in the order mentioned. By interposing the first lithium-tin alloy layer 120 between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121, interfacial delamination between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121 is prevented during discharge, thereby improving cycle characteristics while increasing reversible capacity. <Ein weiterer Gesichtspunkt der Lithium-Sekundärbatterie>

[0061] The lithium secondary battery of the present disclosure may include a negative electrode current collector layer, a first lithium-tin alloy layer, a lithium-magnesium alloy layer, a second lithium-tin alloy layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in the order mentioned. <Zweite Lithium-Zinn-Legierungsschicht>

[0062] The second lithium-tin alloy layer contains a lithium and a tin element and may, if desired, also contain other metal elements that form an alloy with lithium.

[0063] The thickness of the second lithium-tin alloy layer is not particularly limited and may be 0.1 to 15 μm in a fully charged state. The thickness of the second lithium-tin alloy layer is not particularly limited and may be 0.1 μm or more, 0.2 μm or more, 0.4 μm or more, 0.6 μm or more, 0.8 μm or more, or 1.0 μm or more but 15 μm or less, 10 μm or less, 5 μm or less, or 3 μm or less.

[0064] Regarding a method for producing the second lithium-tin alloy layer, reference may be made to the “<<Verfahren zum Herstellen einer Lithium-Sekundärbatterie> >".

[0065] Regarding the negative electrode current collector, the first lithium-tin alloy layer, the negative electrode current collector layer, the lithium-magnesium alloy layer, the electrolyte layer, the positive electrode active material layer and the positive electrode current collector layer, reference can be made to the above description of “<<Lithium-Sekundärbatterie> >".

[0066] Fig. 2 is a schematic drawing illustrating another aspect of the lithium secondary battery of the present disclosure; however, the lithium secondary battery of the present disclosure is not limited to this case.

[0067] The lithium secondary battery 100 is a battery in which the negative electrode current collector layer 110, the first lithium-tin alloy layer 120, the lithium-magnesium alloy layer 121, a second lithium-tin alloy layer 122, the electrolyte layer 130, the positive electrode active material layer 140, and the positive electrode current collector layer 150 are laminated in the order mentioned. By interposing the first lithium-tin alloy layer 120 between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121, interfacial delamination between the negative electrode current collector layer 110 and the lithium-magnesium alloy layer 121 is prevented during discharge, thereby improving cycle characteristics while increasing the reversible capacity.Furthermore, the second lithium-tin alloy layer 122 disposed between the lithium-magnesium alloy layer 121 and the electrolyte layer 130 prevents the interface delamination between the lithium-magnesium alloy layer 121 and the electrolyte layer 130 during discharge, thereby further improving the cycle characteristics. <<Verfahren zum Herstellen einer Lithium-Sekundärbatterie> >

[0068] The lithium secondary battery of the present disclosure can be manufactured by a method comprising the following steps: Obtaining a preliminary lithium secondary battery by laminating a negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, an electrolyte layer, a positive electrode active material layer that retains lithium, and a positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-tin alloy layer; and (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer.

[0069] According to the method for manufacturing the lithium secondary battery of the present disclosure, a lithium secondary battery can be manufactured in which the cycle characteristics can be improved while increasing the reversible capacity. <Erste Metallschicht>

[0070] The first metal layer contains a tin element and can, if desired, also contain other metal elements that form an alloy with lithium.

[0071] The thickness of the first metal layer is not particularly limited and may be 0.01 µm or more, 0.02 µm or more, 0.05 µm or more, 0.10 µm or more but 0.50 µm or less, 0.40 µm or less, 0.30 µm or less, or 0.2 µm or less.

[0072] Specifically, the first metal layer may be formed on the negative electrode current collector by, for example, a sputtering method, but is not limited thereto. <Zweite Metallschicht>

[0073] The second metal layer contains a magnesium element and can, if desired, also contain other metal elements that form an alloy with lithium.

[0074] The thickness of the second metal layer is not particularly limited and may be 0.02 µm or more, 0.05 µm or more, 0.10 µm or more, 0.20 µm or more but 3.0 µm or less, 2.0 µm or less, 1.0 µm or less, or 0.50 µm or less.

[0075] In particular, the second metal layer may be formed, for example, by forming a magnesium layer on the first metal layer by a sputtering process, but is not limited thereto.

[0076] Regarding the negative electrode current collector, the electrolyte layer, the positive electrode active material layer and the positive electrode current collector layer, reference can be made to the above description of “<<Lithium Sekundärbatterie> >". <Vorläufige Lithium-Sekundärbatterie>

[0077] The preliminary lithium secondary battery is a laminate in which the negative electrode current collector layer, the tin-containing first metal layer, the magnesium-containing second metal layer, the electrolyte layer, the positive electrode active material layer that retains lithium, and the positive electrode current collector layer are laminated in the order mentioned.

[0078] In particular, the preliminary lithium secondary battery can be easily formed by, for example, laminating the negative electrode current collector layer, the first metal layer, the second metal layer, the electrolyte layer, the positive electrode current collector layer, and the positive electrode current collector layer in the order mentioned, enclosing the resulting laminate in a laminated film, and then vacuum-sealing and pressing the resultant. (charging process)

[0079] For example, the charging process can be carried out at constant current and constant voltage in a cutoff voltage range of 4.2 V to 3.0 V. During the charging process, lithium is released from the positive electrode active material, which retains the lithium contained in the positive electrode active material layer, and the thus released lithium migrates to the first metal layer and the second metal layer.

[0080] The current intensity (C-rate) in the charging process is not particularly limited and can be 0.01 C or more, 0.02 C or more, 0.03 C or more or 0.05 C or more, but 0.20 C or less, 0.10 C or less, 0.075 C or less or 0.05 C or less.

[0081] There are no specific restrictions on the temperature during charging. The temperature during charging can be 0°C or higher, 10°C or higher, 20°C or higher, 30°C or higher, 40°C or higher, 50°C or higher, or 60°C or higher, but not more than 200°C or lower, 150°C or lower, 120°C or lower, 100°C or lower, or 80°C or lower.

[0082] Fig. 3 is a schematic diagram illustrating one aspect of the preliminary lithium secondary battery in the method for manufacturing the lithium secondary battery of the present disclosure; however, the preliminary lithium secondary battery is not limited to this case. A specific method for manufacturing the lithium secondary battery of Fig. 1 from the preliminary lithium secondary battery of Fig. 3 will now be discussed with reference to Fig. 1 and Fig. 3; however, the procedure is not limited to this case.

[0083] A preliminary lithium secondary battery 200 of Fig. 3 is a laminate in which the negative electrode current collector layer 110, a first metal layer 220, a second metal layer 221, the electrolyte layer 130, the positive electrode active material layer 140, and the positive electrode current collector layer 150 are laminated in the order mentioned. The lithium secondary battery 100 of Fig. 1 can be charged by charging the provisional lithium secondary battery 200 from Fig. 3. In other words, by performing the charging process of the preliminary lithium secondary battery 200, tin of the first metal layer 220 can react with lithium migrating from the positive electrode active material layer 140 to form the first lithium-tin alloy layer 120 of Fig. 1, and magnesium of the second metal layer 221 can react with lithium migrating from the positive electrode active material layer 140 to form the lithium-magnesium alloy layer 121 of Fig. 1, whereby the lithium secondary battery 100 can be manufactured. <Ein weiterer Gesichtspunkt des Verfahrens zum Herstellen einer Lithium-Sekundärbatterie >

[0084] The lithium secondary battery of the present disclosure can also be manufactured by a method including the following steps: Obtaining a preliminary lithium secondary battery by laminating a negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, a tin-containing third metal layer, an electrolyte layer, a positive electrode current collector layer retaining lithium, and a positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the first lithium-tin alloy layer; (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer; and (iii) allow tin of the third metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the second lithium-tin alloy layer. <Dritte Metallschicht>

[0085] The third metal layer contains a tin element and can, if desired, also contain other metal elements that form an alloy with lithium.

[0086] The thickness of the third metal layer is not particularly limited and may be 0.01 µm or more, 0.02 µm or more, 0.05 µm or more, 0.10 µm or more but 0.50 µm or less, 0.40 µm or less, 0.30 µm or less, or 0.2 µm or less.

[0087] In particular, the third metal layer may be formed, for example, by forming a tin layer on the electrolyte layer by a sputtering method, but is not limited thereto.

[0088] Regarding the negative electrode current collector, the electrolyte layer, the positive electrode active material layer and the positive electrode current collector layer, reference can be made to the above description of “<<Lithium Sekundärbatterie> >". With regard to the first metal layer and the second metal layer, reference can be made to the above description of "<<Verfahren zum Herstellen einer Lithium-Sekundärbatterie> >".

[0089] In the preliminary lithium secondary battery, the negative electrode current collector layer, the tin-containing first metal layer, the magnesium-containing second metal layer, the tin-containing third metal layer, the electrolyte layer, the positive electrode active material layer that retains lithium, and the positive electrode current collector layer can be laminated in the order mentioned.

[0090] In particular, the preliminary lithium secondary battery can be easily formed by, for example, laminating the negative electrode current collector layer, the first metal layer, the second metal layer, the third metal layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector layer in the order mentioned, enclosing the resulting laminate in a laminated film, and then vacuum-sealing and pressing the resultant.

[0091] Regarding the charging process, please refer to the above description of "(Charging process)".

[0092] Fig. 4 is a schematic diagram illustrating another aspect of the preliminary lithium secondary battery in the method for manufacturing the lithium secondary battery of the present disclosure; however, the preliminary lithium secondary battery is not limited to this case. A specific method for manufacturing the lithium secondary battery of Fig. 2 from the preliminary lithium secondary battery of Fig. 4 will now be discussed with reference to Fig. 2 and Fig. 4; however, the procedure is not limited to this case.

[0093] A preliminary lithium secondary battery 200 of Fig. 4 is a laminate in which the negative electrode current collector layer 110, the first metal layer 220, the second metal layer 221, the third metal layer 222, the electrolyte layer 130, the positive electrode active material layer 140, and the positive electrode current collector layer 150 are laminated in the order mentioned. The lithium secondary battery 100 of Fig. 2 can be charged by charging the provisional lithium secondary battery 200 from Fig. 4. In other words, by performing the charging process of the preliminary lithium secondary battery 200, tin of the first metal layer 220 can react with lithium migrating from the positive electrode active material layer 140 to form the first lithium-tin alloy layer 120 of Fig. 2; to react magnesium of the second metal layer 221 with lithium migrating from the positive electrode active material layer 140 to form the lithium-magnesium alloy layer 121 of Fig. 2; and to react tin of the third metal layer 222 with lithium migrating from the positive electrode active material layer 140 to form the second lithium-magnesium alloy layer 122 of Fig. 2, whereby the lithium secondary battery 100 can be manufactured. EXAMPLES

[0094] The present disclosure will now be described in more detail with reference to the examples described below; however, the scope of the present disclosure is not limited to the examples described below. <<Beispiel 1> > <Herstellung eines Negativelektrodenstromabnehmers A1 mit einer ersten Metallschicht und einer zweiten Metallschicht>

[0095] On one side of a nickel foil serving as a negative electrode current collector layer, a tin layer with a thickness of 0.1 μm was formed by a sputtering method to form a tin-containing first metal layer on the nickel foil. Subsequently, a magnesium layer with a thickness of 0.2 μm was formed on the surface of this first metal layer on the nickel foil by a sputtering method to form a magnesium-containing second metal layer on the first metal layer, thereby obtaining a negative electrode current collector A1. This negative electrode current collector A1 was a laminate including the negative electrode current collector layer, the first metal layer, and the second metal layer in that order. <Produktion der Elektrolytschicht B1>

[0096] An electrolyte mixture slurry was prepared by mixing a sulfide solid electrolyte (92.6 parts by mass) as the electrolyte, a binder (7.4 parts by mass), and an appropriate amount of butyl butyrate as the dispersant. The resulting electrolyte mixture slurry was coated on a mold release liner with a coating gap of 325 μm, pre-dried at room temperature for 3 hours, and then main-dried at 165°C for 1 hour. After this main drying, the resulting coated liner was punched into two φ14.50 mm pieces, which were then stacked with their coated surfaces facing each other. The resulting liner was then pressed with a pressure of 7.0 tons, after which the mold release liner was peeled off to prepare a self-supporting electrolyte layer B1. <Produktion der Positivelektrodenaktivmaterialschicht C1>

[0097] A positive electrode mixture was prepared by mixing nickel-cobalt-lithium aluminate (NCA, 84.7 parts by mass) as the positive electrode active material, a sulfide solid electrolyte (13.4 parts by mass) as the solid electrolyte, a binder (0.6 parts by mass), a conductive auxiliary agent (1.3 parts by mass), and an appropriate amount of butyl butyrate as the dispersant. Subsequently, the resulting positive electrode mixture slurry was coated onto an aluminum foil serving as a positive electrode current collector with a coating gap of 225 µm, pre-dried at 60°C, and then mainly dried at 165°C for 1 hour to form a positive electrode current collector layer C1 on the aluminum foil. The resulting positive electrode active material layer C1 had a nominal capacity of 3.0 mAh / cm³. 2 and a basis weight of 18.7 mg / cm 2 . <Produktion der vorläufigen Lithium-Sekundärbatterie D1>

[0098] The negative electrode current collector A1 and the positive electrode active material layer C1 were punched out with a size of φ14.50 mm and φ11.28 mm, respectively. Subsequently, the negative electrode current collector A1, the electrolyte layer B1, and the positive electrode active material layer C1 were laminated so that the negative electrode current collector layer, the first metal layer, the second metal layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector layer were arranged in the order mentioned. The resulting laminate was housed in a composite film, which was subsequently vacuum-sealed and then isotropically pressed by cold isotropic pressing at 392 MPa to prepare a preliminary lithium secondary battery D1. Aluminum was used as the positive electrode strip and nickel as the negative electrode strip. <Produktion der Lithium-Sekundärbatterie E1>

[0099] The preliminary lithium secondary battery D1 was clamped with a spring-loaded constant-pressure device at 1 MPa to maintain a constant clamping pressure. Subsequently, this preliminary lithium secondary battery D1 was placed in a 60 °C thermostatic chamber and subjected to a constant current cycle (current density: 0.15 mA / cm 2 , corresponding to 0.05 C) and constant voltage (limiting current density: 0.03 mA / cm 2 , corresponding to 0.01 C) at 60 °C in a cutoff voltage range of 4.2 V to 3.0 V. During the charging process of this constant current constant voltage test of the preliminary lithium secondary battery D1, tin of the first metal layer was reacted with lithium migrating from the positive electrode active material layer C1 to form a first lithium-tin alloy layer, and magnesium of the second metal layer was reacted with lithium migrating from the positive electrode active material layer C1 to form a lithium-magnesium alloy layer, thereby obtaining a lithium secondary battery E1. <Elektrochemische Messung der Lithium-Sekundärbatterie E1>

[0100] The lithium secondary battery E1 was placed in a 25°C thermostatic chamber and subjected to 20 cycles of constant current (current density: 0.15 mA / cm 2 , corresponding to 0.05 C) and constant voltage (limiting current density: 0.03 mA / cm 2 , corresponding to 0.01 C) were carried out at 25°C in a cutoff voltage range of 4.2 V to 3.0 V. The lithium secondary battery E1 had an initial reversible capacity of 2.82 mAh / cm 2 at 25°C and a reversible capacity of 1.46 mAh / cm 2 after 20 cycles at 25°C. <Beispiel 2><Herstellung der Elektrolytschicht B2 mit dritter Metallschicht>

[0101] An electrolyte mixture slurry was prepared by mixing a sulfide solid electrolyte (92.6 parts by mass) as the electrolyte, a binder (7.4 parts by mass), and an appropriate amount of butyl butyrate as the dispersant. The resulting electrolyte mixture slurry was coated onto a mold release liner with a coating gap of 325 µm, pre-dried at room temperature for 3 hours, and then main-dried at 165°C for 1 hour. After this main drying, the resulting coated liner was punched into two φ14.50 mm pieces, which were then stacked with their coated surfaces facing each other. The resulting liner was then pressed with a pressure of 7.0 tons, after which the mold release liner was peeled off to form a self-supporting electrolyte layer.Thereafter, a tin layer having a thickness of 0.1 µm was formed on one side of the thus obtained self-supporting electrolyte layer by a sputtering method to form a tin-containing third metal layer on the electrolyte layer, thereby preparing an electrolyte layer B2. <Produktion der vorläufigen Lithium-Sekundärbatterie D2>

[0102] A preliminary lithium secondary battery D2 was manufactured in the same manner as in Example 1, except that the electrolyte layer B2 was used instead of the electrolyte layer B1, and the negative electrode current collector layer A1, the electrolyte layer B2, and the positive electrode active material layer C1 were laminated such that the negative electrode current collector layer, the first metal layer, the second metal layer, the third metal layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector layer were arranged in the order mentioned. <Produktion der Lithium-Sekundärbatterie E2>

[0103] The preliminary lithium secondary battery D2 was clamped with a spring-loaded constant-pressure device at 1 MPa to maintain a constant clamping pressure. Subsequently, this preliminary lithium secondary battery D2 was placed in a 60°C thermostatic chamber and subjected to a constant current cycle (current density: 0.15 mA / cm 2 , corresponding to 0.05 C) and constant voltage (limiting current density: 0.03 mA / cm 2 , corresponding to 0.01 C) at 60 °C in a cutoff voltage range of 4.2 V to 3.0 V. By the charging process of this constant current constant voltage test, the tin of the first metal layer was allowed to react with the lithium migrating from the positive electrode active material layer C1 to form a first lithium-tin alloy layer, magnesium of the second metal layer was allowed to react with lithium migrating from the positive electrode active material layer C1 to form a lithium-magnesium alloy layer, and tin of the third metal layer was allowed to react with lithium migrating from the positive electrode active material layer C1 to form a second lithium-tin alloy layer, thereby obtaining a lithium secondary battery E2. <SEM-EDX-Messung der Lithium-Sekundärbatterie E2>

[0104] For a cross-section of the lithium secondary battery E2 after the first charge at 60°C, scanning electron microscopy (SEM) observations of a secondary electron image obtained at an accelerating voltage of 5 kV and elemental mapping by energy dispersive X-ray (EDX) analysis were performed. Fig. 5 shows the results of EDX mapping analysis of the lithium secondary battery E2, and Fig. Figure 6 shows an SEM cross-sectional image of the lithium secondary battery E2 and a schematic drawing of the cross-sectional structure. From the SEM-EDX observation, it was confirmed that in the lithium secondary battery E2, after the first charge, the negative electrode current collector layer 110, the first lithium-tin alloy layer 120, the lithium-magnesium alloy layer 121, the second lithium-tin alloy layer 122, and the electrolyte layer 130 were laminated in the order mentioned. <Elektrochemische Messung der Lithium-Sekundärbatterie E2>

[0105] The electrochemical measurement of the lithium secondary battery E2 was performed in the same manner as in Example 1. The initial reversible capacity of the lithium secondary battery E2 at 25°C and the reversible capacity of the lithium secondary battery E2 after 20 cycles at 25°C are shown in Table 1. <<Vergleichsbeispiel 1> ><Herstellung eines Negativelektrodenstromabnehmers A2 mit zweiter Metallschicht>

[0106] On one side of a nickel foil serving as the negative electrode current collector layer, a magnesium layer with a thickness of 0.2 μm was formed by a sputtering method to form a magnesium-containing second metal layer on the nickel foil, thereby obtaining a negative electrode current collector A2. The thus obtained negative electrode current collector A2 was a laminate comprising the negative electrode current collector layer and the second metal layer in the order mentioned. <Produktion der vorläufigen Lithium-Sekundärbatterie d1>

[0107] A preliminary lithium secondary battery d1 was manufactured in the same manner as in Example 1, except that the negative electrode current collector A2 was used instead of the negative electrode current collector A1, and the negative electrode current collector A2, the electrolyte layer B1, and the positive electrode active material layer C1 were laminated such that the negative electrode current collector layer, the second metal layer, the electrolyte layer, the positive electrode active material layer, and the positive electrode current collector layer were arranged in the order mentioned. <Herstellung und elektrochemische Messung der Lithium-Sekundärbatterie e1>

[0108] A lithium secondary battery e1 was manufactured in the same manner as in Example 1, except that the preliminary lithium secondary battery d1 was used instead of the preliminary lithium secondary battery D1. The electrochemical measurement of the lithium secondary battery e1 was performed in the same manner as in Example 1. The initial reversible capacity of the lithium secondary battery e1 at 25°C and the reversible capacity of the lithium secondary battery e1 after 20 cycles at 25°C are shown in Table 1. <<Vergleichsbeispiel 2> ><Produktion der vorläufigen Lithium-Sekundärbatterie d2>

[0109] A preliminary lithium secondary battery d2 was manufactured in the same manner as in Example 1, except that the negative electrode current collector A2 was used instead of the negative electrode current collector A1, the electrolyte layer B2 was used instead of the electrolyte layer B1, and the negative electrode current collector A2, the electrolyte layer B2, and the positive electrode active material layer C1 were laminated such that the negative electrode current collector layer, the second metal layer, the third metal layer, the electrolyte layer, the negative electrode active material layer, and the positive electrode current collector layer were arranged in the order mentioned. <Herstellung und elektrochemische Messung der Lithium-Sekundärbatterie e2>

[0110] A lithium secondary battery e2 was manufactured in the same manner as in Example 1, except that the preliminary lithium secondary battery d2 was used instead of the preliminary lithium secondary battery D1. The electrochemical measurement of the lithium secondary battery e2 was performed in the same manner as in Example 1. The initial reversible capacity of the lithium secondary battery e2 at 25°C and the reversible capacity of the lithium secondary battery e2 after 20 cycles at 25°C are shown in Table 1.

[0111] Table 1 shows the evaluation results of the electrochemical measurement of Examples 1 and 2 and Comparative Examples 1 and 2.

[0108] [Table 1] Example 1 Example 2 Comparison example 1 Comparison example 2 Preliminary lithium secondary battery Provisional lithium secondary battery D1 Provisional lithium secondary battery D2 Provisional lithium secondary battery d1 Provisional lithium secondary battery d2 Negative electrode current collector Negative electrode current collector A1 Negative electrode current collector A1 Negative electrode current collector A2 Negative electrode current collector A2 First metal layer Sn layer (0.1 µm) Sn layer (0.1 µm) no no Second metal layer Mg layer (0.2 µm) Mg layer (0.2 µm) Mg layer (0.2 µm) Mg layer (0.2 µm) Electrolyte layer Electrolyte layer B1 Electrolyte layer B2 Electrolyte layer B1 Electrolyte layer B2 Third metal layer no Sn layer (0.1 µm) no Sn layer (0.1 µm) Positive electrode active material layer Positive electrode active material layer C1 Positive electrode active material layer C1 Positive electrode active material layer C1 Positive electrode active material layer C1 Lithium secondary battery Lithium secondary battery E1 Lithium secondary battery E2 Lithium secondary battery e1 Lithium secondary battery e2 First lithium-tin alloy layer Li-Sn layer Li-Sn layer no no Lithium-magnesium alloy layer Li-Mg layer Li-Mg layer Li-Mg layer Li-Mg layer Second lithium-tin alloy layer no Li-Sn layer no Li-Sn layer Evaluation results Initial reversible capacity (25°C) [mAh / cm 2 ] 2,82 2,89 2,24 2,41 Reversible capacity after 20 cycles (25°C) [mAh / cm 2 ] 1,46 2,77 0,48 1,08

[0112] The lithium secondary batteries E1 and E2 in which the first lithium-tin alloy layer was disposed had a higher initial reversible capacity at 25°C compared to the lithium secondary batteries e1 and e2 in which the first lithium-tin alloy layer was not disposed. This is presumed because the disposition of the first lithium-tin alloy layer between the negative electrode current collector layer and the lithium-magnesium alloy layer inhibited the interfacial delamination between the negative electrode current collector layer and the lithium-magnesium alloy layer during discharge, thereby increasing the reversible capacity and improving the cycle characteristics.

[0113] The following is considered to be the factor that enabled the first lithium-tin alloy layer to prevent the interfacial delamination between the negative electrode current collector layer and the lithium-magnesium alloy layer. During discharge, from the standpoint of the reaction potential, the dealloyation of lithium contained in the lithium-tin alloy layer proceeds preferentially over the dealloyation of lithium contained in the first lithium-tin alloy layer; therefore, the lithium-tin alloy layer contracts greatly. On the other hand, since the lithium-tin alloy layer contracts less than the lithium-magnesium alloy layer, the lithium-tin alloy layer relaxes the contraction of the lithium-magnesium alloy layer, and it is presumed that the above-described interfacial delamination was thereby prevented.

[0114] Furthermore, the lithium secondary battery E2, in which the second lithium-tin alloy layer was arranged, maintained a high reversible capacity of 2.77 mAh / cm even after 20 cycles. 2 This is believed to be because the second lithium-tin alloy layer between the lithium-magnesium alloy layer and the electrolyte layer prevented interfacial delamination between the lithium-magnesium alloy layer and the electrolyte layer during discharge, thereby improving the cycling characteristics. It is noted here that the inhibition of interfacial delamination by the second lithium-tin alloy layer is likely due to the same factor as the inhibition of interfacial delamination by the first lithium-tin alloy layer.

[0115] Preferred embodiments of the lithium secondary battery of the present disclosure have been described in this way, and those of ordinary skill in the art will understand that various modifications can be made without departing from the scope of the claims. LIST OF REFERENCE SYMBOLS 100 lithium secondary battery 110 Negative electrode current collector layer 120 first lithium-tin alloy layer 121 Lithium-magnesium alloy layer 122 second lithium-tin alloy layer 130 Electrolyte layer 140 Positive electrode active material layer 150 positive electrode current collector layer 200 preliminary lithium secondary batteries 220 first metal layer 221 second metal layer 222 third metal layer QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-184513

[0004] JP 2021-132033

[0004] < / positivelektrodenstromabnehmerschicht> < / positivelektrodenaktivmaterialschicht> < / negativelektrodenstromabnehmerschicht>

Claims

[1] A lithium secondary battery comprising a negative electrode current collector layer, a first lithium-tin alloy layer, a lithium-magnesium alloy layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector layer in the order mentioned. [2] The lithium secondary battery according to claim 1, wherein the first lithium-tin alloy layer has a thickness of 0.1 to 15 µm in a fully charged state. [3] The lithium secondary battery according to claim 1, wherein the lithium-magnesium alloy layer has a thickness of 0.1 to 40 µm in a fully charged state. [4] The lithium secondary battery according to claim 1, comprising the negative electrode current collector layer, the first lithium-tin alloy layer, the lithium-magnesium alloy layer, a second lithium-tin alloy layer, the electrolyte layer, the positive electrode current collector layer, and the positive electrode current collector layer in the order mentioned. [5] A lithium secondary battery according to claim 4, wherein, in a fully charged state, the first lithium-tin alloy layer has a thickness of 0.1 to 15 µm, and the second lithium-tin alloy layer has a thickness of 0.1 to 15 µm. [6] A method of manufacturing the lithium secondary battery according to any one of claims 1 to 5, the method comprising the following steps: Obtaining a preliminary lithium secondary battery by laminating the negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, the electrolyte layer, the positive electrode active material layer that retains lithium, and the positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-tin alloy layer; and (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer. [7] A method of manufacturing the lithium secondary battery according to claim 4 or 5, the method comprising the following steps: Obtaining the preliminary lithium secondary battery by laminating the negative electrode current collector layer, a tin-containing first metal layer, a magnesium-containing second metal layer, a tin-containing third metal layer, the electrolyte layer, the positive electrode current collector layer retaining lithium, and the positive electrode current collector layer in the order mentioned; and Performing a charging process of the preliminary lithium secondary battery to: (i) allow tin of the first metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the first lithium-tin alloy layer; (ii) allow magnesium of the second metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the lithium-magnesium alloy layer; and (iii) allow tin of the third metal layer to react with lithium migrating from the positive electrode active material layer, thereby forming the second lithium-tin alloy layer.

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