Battery

Abstract

The battery (1000) of the present disclosure sequentially includes a positive electrode (101), a first electrolyte layer (102), a second electrolyte layer (103), and a negative electrode (104). The first electrolyte layer (102) contains a first solid electrolyte material and a second solid electrolyte material. In the first electrolyte layer (102), the mass ratio of the second solid electrolyte material to the first solid electrolyte material is greater than 0.05 and less than 1. The second electrolyte layer (103) contains the second solid electrolyte material. The first solid electrolyte material is formed of Li, M, O, and X. In the first solid electrolyte material, M is at least one element selected from metal elements and metalloid elements other than Li, and X is at least one element selected from Cl, Br, and I. The second solid electrolyte material has a composition different from that of the first solid electrolyte material.

Description

Technical Field

[0001] The present disclosure relates to a battery. Background Art

[0002] In Patent Document 1, a battery is disclosed which sequentially includes a positive electrode; a first electrolyte layer containing a first solid electrolyte material; a second electrolyte layer containing a second solid electrolyte material; and a negative electrode. Among them, the reduction potential of the second solid electrolyte material is lower than the reduction potential of the first solid electrolyte material.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: International Publication No. 2019 / 146294 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] An object of the present disclosure is to provide a battery having high cycle characteristics.

[0008] Means for Solving the Problems

[0009] The battery of the present disclosure sequentially includes a positive electrode, a first electrolyte layer, a second electrolyte layer, and a negative electrode. Among them, the first electrolyte layer contains a first solid electrolyte material and a second solid electrolyte material.

[0010] In the first electrolyte layer, the mass ratio of the second solid electrolyte material to the first solid electrolyte material is greater than 0.05 and less than 1.

[0011] The second electrolyte layer contains the second solid electrolyte material.

[0012] The first solid electrolyte material is formed of Li, M, O, and X.

[0013] In the first solid electrolyte material, M is at least one element selected from metal elements and metalloid elements other than Li, and X is at least one element selected from Cl, Br, and I. And

[0014] The second solid electrolyte material has a composition different from that of the first solid electrolyte material.

[0015] Advantages of the Invention

[0016] The present disclosure can provide a battery having high cycle characteristics. Brief Description of the Drawings

[0017] Figure 1 A cross-sectional view showing the battery 1000 of the embodiment. Detailed Embodiments

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0019] Figure 1 A cross-sectional view of the battery 1000 showing an embodiment.

[0020] As Figure 1 shown, the battery 1000 of the embodiment sequentially includes a positive electrode 101, a first electrolyte layer 102, a second electrolyte layer 103, and a negative electrode 104.

[0021] The first electrolyte layer 102 contains a first solid electrolyte material and a second solid electrolyte material. In the first electrolyte layer 102, the mass ratio of the second solid electrolyte material to the first solid electrolyte material is greater than 0.05 and less than 1.

[0022] The second electrolyte layer 103 contains the second solid electrolyte material.

[0023] The second solid electrolyte material has a composition different from that of the first solid electrolyte material.

[0024] The first solid electrolyte material is formed of Li, M, O, and X. Among them, M is at least one element selected from metal elements and metalloid elements other than Li. X is at least one element selected from Cl, Br, and I.

[0025] The battery 1000 of the embodiment has high cycle characteristics.

[0026] A battery having high cycle characteristics means a battery in which the retention rate of the charge-discharge capacity is high even after repeated charge-discharge cycles.

[0027] In the present disclosure, "metalloid element" means B, Si, Ge, As, Sb, and Te.

[0028] In the present disclosure, "metal element" means:

[0029] (i) all elements (except hydrogen) included in Groups 1 to 12 of the periodic table; and

[0030] (ii) all elements (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se) included in Groups 13 to 16.

[0031] Among them, the inventors of the present invention studied an existing battery as disclosed in Patent Document 1, that is, a battery including a positive electrode, an electrolyte layer formed of a first solid electrolyte material, an electrolyte layer formed of a second solid electrolyte material, and a negative electrode in sequence. The inventors of the present invention found that: for the existing battery as disclosed in Patent Document 1, for example, cracks may occur in the electrolyte layer. This crack occurs, for example, during battery manufacturing. Due to the occurrence of this crack, the cycle characteristics of the conventional battery are reduced. On the other hand, for the battery 1000 of the embodiment, as described above, the first electrolyte layer 102 contains not only the first solid electrolyte material but also the second solid electrolyte material contained in the second electrolyte layer 103. That is, the first electrolyte layer 102 and the second electrolyte layer 103 contain the second solid electrolyte material as a common material. Further, in the first electrolyte layer 102, the mass ratio of the second solid electrolyte material to the first solid electrolyte material is greater than 0.05 and less than 1. By making the first electrolyte layer 102 and the second electrolyte layer have such a structure, the battery 1000 of the embodiment can suppress the occurrence of cracks.

[0032] In the first electrolyte layer 102, when the mass ratio of the second solid electrolyte material to the first solid electrolyte material exceeds 0.05, the occurrence of cracks can be suppressed. Thereby, the cycle characteristics of the battery 1000 are improved. When the above mass ratio is less than 1, the internal resistance of the battery 1000 is reduced. Thereby, the discharge capacity of the battery 1000 is increased.

[0033] The first solid electrolyte material has a high ionic conductivity. Therefore, the first solid electrolyte material can be used to obtain a battery with high output characteristics. The first solid electrolyte material also has excellent thermal stability.

[0034] The first solid electrolyte material is an example of a halogen oxide solid electrolyte. As an example of other halogen oxide solid electrolytes, materials formed of Li, O, and X (X is at least one element selected from Cl, Br, and I) can be cited. The first solid electrolyte material is a material containing M in addition to containing Li, O, and X. The first solid electrolyte material containing M has a higher ionic conductivity than the material formed of Li, O, and X. Therefore, by using the first solid electrolyte material, the discharge capacity of the battery can be increased.

[0035] In order to further improve the cycle characteristics of the battery 1000, in the first electrolyte layer 102, the mass ratio of the second solid electrolyte material to the first solid electrolyte material can exceed 0.05 and be 0.50 or less. In order to further improve the cycle characteristics of the battery 1000, the mass ratio can also be 0.10 to 0.50.

[0036] In order to improve the ionic conductivity of the first solid electrolyte material, M may contain at least one element selected from Nb and Ta. The molar ratio of Li to M may be 0.60 to 2.4, and the molar ratio of O to X may be 0.16 to 0.35. Such a first solid electrolyte material has high ionic conductivity.

[0037] The first solid electrolyte material may be a material represented by the following chemical formula (1).

[0038] Li α MO β X γ (1)

[0039] Wherein, in chemical formula (1), the following mathematical formulas 1.0 ≤ α ≤ 1.2, 1.0 ≤ β ≤ 1.3 and 3.6 ≤ γ ≤ 4.0 are satisfied. The solid electrolyte material represented by chemical formula (1) has high ionic conductivity.

[0040] In chemical formula (1), M may be at least one element selected from Nb and Ta. In this case, in chemical formula (1), the mathematical formula: γ = 5 + α - 2β is satisfied. Such a first solid electrolyte material has higher ionic conductivity.

[0041] The first solid electrolyte material may be a material represented by the following chemical formula (3).

[0042] Li x MO y X (5+x-2y) (3)

[0043] Wherein, in chemical formula (3), the following mathematical formulas 0.1 < x < 7.0 and 0.4 < y < 1.9 are satisfied. The solid electrolyte material represented by chemical formula (3) has high ionic conductivity.

[0044] As described above, the second solid electrolyte material has a composition different from that of the first solid electrolyte material. The second solid electrolyte material may have a reduction potential lower than that of the first solid electrolyte material. By making the second solid electrolyte material have a lower reduction potential than the first solid electrolyte material, the reduction of the first solid electrolyte material can be inhibited. As described above, the first solid electrolyte material has high ionic conductivity. By inhibiting the reduction of the first solid electrolyte material, the charge-discharge efficiency of the battery 1000 is improved.

[0045] The first electrolyte layer 102 is preferably not in contact with the negative electrode 104. By preventing the contact between the first electrolyte layer 102 and the negative electrode 104 through the electrochemically stable second electrolyte layer 103, the reduction of the first solid electrolyte material contained in the first electrolyte layer 102 can be inhibited. As a result, the battery 1000 has high charge-discharge efficiency.

[0046] The voltage at which the reduction decomposition of the solid electrolyte (i.e., the reduction potential) can be measured by the cyclic voltammetry described in the non-patent literature "Adv. Energy Mater. 2016, 20, 1501590 - 1501599."

[0047] The second solid electrolyte material may be a halide solid electrolyte (excluding oxyhalide solid electrolytes).

[0048] Similar to the first solid electrolyte material, the halide solid electrolyte has high ionic conductivity and excellent thermal stability. Therefore, the battery 1000 containing the first solid electrolyte material and the second solid electrolyte material has high output characteristics and thermal stability.

[0049] The second solid electrolyte material may be formed of Li, M', and X'. Among them, M' is at least one element selected from metal elements and metalloid elements other than Li, and X' is at least one element selected from Cl, Br, and I. Such a second solid electrolyte material has high ionic conductivity.

[0050] To increase the ionic conductivity of the second solid electrolyte material, M' may contain Y (i.e., yttrium). By this increase in ionic conductivity, the battery 1000 has a high discharge capacity.

[0051] The second solid electrolyte material containing Y may be, for example, a material represented by Li a Me b Y c X' 6 where the mathematical formula: a + mb + 3c = 6 and c > 0 is satisfied. Me is at least one element selected from metal elements and metalloid elements other than Li and Y. m represents the valence of Me.

[0052] To further increase the ionic conductivity of the second solid electrolyte material, Me may be at least one element selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0053] The second solid electrolyte material may be a material represented by the following chemical formula (2).

[0054] li 6-3z Y z X' 6 (2)

[0055] Among them, in the chemical formula (2), the mathematical formula: 0 < z < 2 is satisfied. The solid electrolyte material represented by the chemical formula (2) has high ionic conductivity. The second solid electrolyte material may be Li 3YCl 6 。

[0056] Another example of the halide solid electrolyte is Li 2 MgX’ 4 、Li 2 FeX’ 4 、Li(Al, Ga, In)X’ 4 or Li 3 (Al, Ga, In)X’ 6 。“(Al, Ga, In)” means “at least one element selected from Al, Ga, and In”.

[0057] In order to increase the discharge capacity of the battery 1000, the second solid electrolyte material may also be a sulfide solid electrolyte.

[0058] Examples of the sulfide solid electrolyte used as the second solid electrolyte material are Li 2 S-P 2 S 5 、Li 2 S-SiS 2 、Li 2 S-B 2 S 3 、Li 2 S-GeS 2 、Li 3.25 Ge 0.25 P 0.75 S 4 or Li 10 GeP 2 S 12 。Furthermore, LiX”, Li 2 O, M”O or Li p M”O q may be added. Herein, M” is at least one element selected from P, Si, Ge, B, Al, Ga, In, Fe, and Zn. p and q are both natural numbers. X” is at least one element selected from F, Cl, Br, and I.

[0059] In order to increase the output of the battery 1000 while suppressing the short circuit between the positive electrode 101 and the negative electrode 104, the total thickness of the first electrolyte layer 102 and the second electrolyte layer 103 may be 1 μm to 300 μm. 2 S-P 2 S 5 。

[0060]

[0061] ​The first electrolyte layer 102 may have the same thickness as the second electrolyte layer 103.

[0062] In order to increase the discharge capacity of the battery 1000, in the first electrolyte layer 102, the total of the first solid electrolyte material and the second solid electrolyte material may be 70% or more, or may be 90% or more, with respect to the total mass of the first electrolyte layer 102. In order to increase the discharge capacity of the battery 1000, the first electrolyte layer 102 may also be composed only of the first solid electrolyte material and the second solid electrolyte material.

[0063] In order to increase the discharge capacity of the battery 1000, in the second electrolyte layer 103, the second solid electrolyte material may be 70% or more, or may be 90% or more, with respect to the total mass of the second electrolyte layer 103. In order to increase the discharge capacity of the battery 1000, the second electrolyte layer 103 may also be composed only of the second solid electrolyte material.

[0064] The positive electrode 101 contains a positive electrode active material and an electrolyte material.

[0065] The positive electrode active material is a material capable of inserting and extracting metal ions such as lithium ions.

[0066] Examples of the positive electrode active material are lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal sulfur oxides, or transition metal nitrogen oxides. Examples of the lithium-containing transition metal oxides are Li(NiCoAl)O 2 、Li(NiCoMn)O 2 or LiCoO 2 。By using a lithium-containing transition metal oxide as the positive electrode active material, the manufacturing cost can be suppressed, and the average discharge voltage of the battery 1000 can be increased.

[0067] In order to further increase the discharge capacity and energy density of the battery, the positive electrode active material may be lithium nickel cobalt manganese oxide.

[0068] The positive electrode 101 may also contain positive electrode active material particles as the positive electrode active material. In this case, the positive electrode active material may have a median particle size of 0.1 μm to 100 μm. When the positive electrode active material has a median particle size of 0.1 μm or more, in the positive electrode 101, the positive electrode active material and the electrolyte material can be well dispersed. As a result, the charge-discharge characteristics of the battery 1000 are improved. When the positive electrode active material has a median particle size of 100 μm or less, the lithium diffusion rate in the positive electrode active material is increased. As a result, the battery can operate at a high output.

[0069] The electrolyte material contained in the positive electrode 101 is, for example, a solid electrolyte.

[0070] The electrolyte material contained in the positive electrode 101 may also be the first solid electrolyte material. That is, the positive electrode 101 may also contain the first solid electrolyte material. By making the positive electrode 101 contain the same material as the first electrolyte layer 102, the charge and discharge capacity and output characteristics of the battery are improved.

[0071] Hereinafter, a material different from the first solid electrolyte material and the second solid electrolyte material is referred to as a third solid electrolyte material.

[0072] The positive electrode 101 may contain a second solid electrolyte material or a third solid electrolyte material.

[0073] The third solid electrolyte material may be a sulfide solid electrolyte.

[0074] An example of a sulfide solid electrolyte is Li 2 SP 2 S 5 , Li 2 S-SiS 2 , Li 2 SB 2 S 3 , Li 2 S-GeS 2 , Li 3.25 Ge 0.25 P 0.75 S 4 or Li 10 G 2 S 12 They can also add LiX", Li 2 O, M"O q or Li p M”O q . Wherein, X" is at least one element selected from F, Cl, Br and I. M" is at least one element selected from P, Si, Ge, B, Al, Ga, In, Fe and Zn. p and q are both natural numbers.

[0075] The third solid electrolyte material may be an oxide solid electrolyte.

[0076] Examples of oxide solid electrolytes are:

[0077] (i)LiTi 2 (PO 4 ) 3 NASICON type solid electrolytes such as or their element substitutions,

[0078] (ii) (LaLi)TiO 3 Perovskite solid electrolytes

[0079] (iii) Li 14 ZnGe 4 O 16 、Li 4 SiO 4 、LiGeO 4 or a LISICON-type solid electrolyte such as its elemental substitute,

[0080] (iv) Li 7 La 3 Zr 2 O 12 or a garnet-type solid electrolyte such as its elemental substitute,

[0081] (v) Li 3 PO 4 or its N substitute, or

[0082] (vi) A glass or glass-ceramic formed by adding Li 2 or Li 3 BO 3 to a Li-B-O compound such as 2 SO 4 or Li 2 CO 3 .

[0083] The third solid electrolyte material may also be a polymer solid electrolyte.

[0084] Examples of the polymer solid electrolyte are compounds of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. The polymer compound having an ethylene oxide structure can contain a large amount of the lithium salt, and thus can further improve the ionic conductivity.

[0085] Examples of the lithium salt are LiPF 6 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiSO 3 CF 3 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiN(SO 2 CF 3 )(SO 2 C 4 F 9 ) or LiC(SO 2 CF 3) 3 One kind of lithium salt selected from them can be used alone. Alternatively, a mixture of two or more lithium salts selected from them can also be used.

[0086] The third solid electrolyte material can be a complex hydride solid electrolyte.

[0087] Examples of the complex hydride solid electrolyte are LiBH 4 -LiI or LiBH 4 -P 2 S 5 .

[0088] The third solid electrolyte material can be a different oxohalide solid electrolyte from the first solid electrolyte material. Examples of the oxohalide solid electrolyte are Li 3 OX” or Li 2 HOX”. Wherein, X” is at least one element selected from F, Cl, Br and I.

[0089] The shape of the electrolyte material contained in the positive electrode 101 is not limited. Examples of the shape are needle-like, spherical or ellipsoidal. For example, the shape of the electrolyte material can also be particles.

[0090] When the shape of the electrolyte material contained in the positive electrode 101 is particulate (e.g., spherical), the median particle size of the electrolyte material can be 100 μm or less, or can be 10 μm or less. Thus, in the positive electrode 101, the positive electrode active material and the electrolyte material can be well dispersed. Due to this good dispersion, the battery has high charge-discharge characteristics.

[0091] The electrolyte material contained in the positive electrode 101 can have a smaller median particle size than the positive electrode active material. Thus, in the positive electrode 101, the electrolyte material and the positive electrode active material can be better dispersed. Due to this good dispersion, the battery has high charge-discharge efficiency.

[0092] In order to improve the energy density and output of the battery 1000, in the positive electrode 101, the ratio of the volume of the positive electrode active material to the sum of the volumes of the positive electrode active material and the electrolyte material can be 0.30 to 0.95.

[0093] In order to improve the energy density and output of the battery 1000, the positive electrode 101 can have a thickness of 10 μm to 500 μm.

[0094] The negative electrode 104 contains a negative electrode active material and an electrolyte material.

[0095] The negative electrode active material is a material capable of intercalating and deintercalating metal ions such as lithium ions.

[0096] The negative electrode active material is, for example, a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a single metal or an alloy. Examples of the metal material are lithium metal or a lithium alloy. Examples of the carbon material are natural graphite, coke, carbon during graphitization, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0097] The negative electrode 104 may contain negative electrode active material particles as the negative electrode active material. In this case, the negative electrode active material may have a median particle size of 0.1 μm to 100 μm. When the negative electrode active material has a median particle size of 0.1 μm or more, the negative electrode active material and the electrolyte material can be well dispersed in the negative electrode 104. Thereby, the charge-discharge characteristics of the battery are improved. When the negative electrode active material has a median particle size of 100 μm or less, the lithium diffusion rate in the negative electrode active material is increased. Thereby, the battery can operate at a high output.

[0098] The electrolyte material contained in the negative electrode 104 is, for example, a solid electrolyte.

[0099] The electrolyte material contained in the negative electrode 104 may be the second solid electrolyte material. That is, the negative electrode 104 may also contain the second solid electrolyte material.

[0100] The electrolyte material contained in the negative electrode 104 may be the above-mentioned third solid electrolyte material.

[0101] The shape of the electrolyte material contained in the negative electrode 104 is not limited. Examples of the shape are needle-like, spherical, or ellipsoidal. For example, the shape of the electrolyte material may also be particles.

[0102] When the shape of the electrolyte material contained in the negative electrode 104 is particle-like (e.g., spherical), the median particle size of the electrolyte material may be 100 μm or less, or may be 10 μm or less. Thereby, in the negative electrode 104, the negative electrode active material and the electrolyte material can be well dispersed. Due to this good dispersion, the battery has high charge-discharge characteristics.

[0103] The electrolyte material contained in the negative electrode 104 may have a smaller median particle size than the negative electrode active material. Thereby, in the negative electrode 104, the electrolyte material and the positive electrode active material can be better dispersed. Due to this good dispersion, the battery has a high charge-discharge efficiency.

[0104] From the viewpoints of the energy density and output of the battery, in the negative electrode 104, the ratio of the volume of the negative electrode active material to the total volume of the negative electrode active material and the electrolyte material may be 0.30 to 0.95.

[0105] To increase the energy density and output of the battery, the negative electrode 104 may have a thickness of 10 μm to 500 μm.

[0106] To reduce the interfacial resistance, at least a part of the surface of the positive electrode active material or at least a part of the surface of the negative electrode active material may be coated with a coating material.

[0107] As the coating material, a material with low electronic conductivity can be used. Examples of the coating material are sulfide solid electrolytes, polymer solid electrolytes, complex hydride solid electrolytes, or halide solid electrolytes exemplified as the third solid electrolyte material. From the viewpoint of potential stability, a preferred example of the coating material is an oxide solid electrolyte. By using an oxide solid electrolyte as the coating material, the battery has higher charge-discharge efficiency.

[0108] Other examples of the oxide solid electrolyte used as the coating material are:

[0109] (i) Li-Nb-O compounds such as LiNbO 3 ;

[0110] (ii) Li-B-O compounds such as LiBO 2 or Li 3 BO 3 ;

[0111] (iii) Li-Al-O compounds such as LiAlO 2 ;

[0112] (iv) Li-Si-O compounds such as Li 4 SiO 4 ;

[0113] (v) Li-Ti-O compounds such as Li 2 SO 4 or Li 4 Ti 5 O 12 ;

[0114] (vi) Li-Zr-O compounds such as Li 2 ZrO 3 ;

[0115] (vii) Li-Mo-O compounds such as Li 2 MoO 3 ;

[0116] (viii) Li-V-O compounds such as LiV 2 O 5 ; or

[0117] (ix) Li 2 WO 4 Li-W-O compounds such as

[0118] To increase the output of the battery, at least one selected from the first electrolyte layer 102 and the second electrolyte layer 103 may contain the above-described third solid electrolyte material.

[0119] To facilitate the transfer of lithium ions and improve the output characteristics of the battery, at least one selected from the positive electrode 101, the first electrolyte layer 102, the second electrolyte layer 103, and the negative electrode 104 may contain a non-aqueous electrolyte solution, a gel electrolyte, or an ionic liquid.

[0120] The non-aqueous electrolyte solution contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0121] Examples of the non-aqueous solvent are a cyclic carbonate solvent, a chain carbonate solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent. Examples of the cyclic carbonate solvent are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the chain carbonate solvent are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of the chain ether solvent are 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of the cyclic ester solvent are γ-butyrolactone. Examples of the chain ester solvent are methyl acetate. Examples of the fluorine solvent are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, ethyl methyl fluorocarbonate, or dimethyl fluorocarbonate. One non-aqueous solvent selected from them may be used alone. Alternatively, a mixture of two or more non-aqueous solvents selected from them may also be used.

[0122] Examples of the lithium salt are LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiSO 3 CF 3 , LiN(SO 2 CF 3 ), 2 , LiN(SO 2 C 2 F 5 ), 2 , LiN(SO 2 CF 3 )(SO 2 C 4 F 9 ), or LiC(SO 2 CF 3 ), 3One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0123] The concentration of the lithium salt is, for example, in the range of 0.5 mol / L to 2 mol / L.

[0124] As the gel electrolyte, a polymer material impregnated with a non-aqueous electrolyte can be used. Examples of the polymer material are polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0125] Examples of cations contained in ionic liquids are:

[0126] (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium,

[0127] (ii) an aliphatic cyclic ammonium such as a pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium or piperidinium, or

[0128] (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium and imidazolinium cations.

[0129] An example of an anion contained in an ionic liquid is PF 6 - , BF 4 - , SbF 6 - , AsF 6 - 、SO 3 CF 3 - 、N(SO 2 CF 3 ) 2 - 、N(SO 2 C 2 F 5 ) 2 - 、N(SO 2 CF 3 )(SO 2 C 4 F 9 ) - or C(SO 2 CF 3 ) 3 - The ionic liquid may also contain lithium salts.

[0130] In order to improve the adhesion between particles, at least one selected from the positive electrode 101, the first electrolyte layer 102, the second electrolyte layer 103, and the negative electrode 104 may also contain a binder.

[0131] Examples of the binder are polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamideimide, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, hexyl polyacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, or carboxymethyl cellulose.

[0132] Copolymers can also be used as binders. Examples of such binders are copolymers of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Mixtures of two or more selected from the above materials can also be used as binders.

[0133] In order to improve the electron conductivity, at least one selected from the positive electrode 101 and the negative electrode 104 may contain a conductive additive.

[0134] Examples of the conductive additive are:

[0135] (i) Graphite such as natural graphite or artificial graphite,

[0136] (ii) Carbon black such as acetylene black or Ketjen black,

[0137] (iii) Conductive fibers such as carbon fibers or metal fibers,

[0138] (iv) Carbon fluoride,

[0139] (v) Metal powders such as aluminum,

[0140] (vi) Conductive whiskers such as zinc oxide or potassium titanate,

[0141] (vii) Conductive metal oxides such as titanium oxide, or

[0142] (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene.

[0143] In order to reduce costs, the conductive additives of (i) or (ii) above can also be used.

[0144] Examples of the shape of the battery of the first embodiment are coin type, cylindrical type, square type, sheet type, button type, flat type, or laminated type.

[0145] <Method for manufacturing the first solid electrolyte material>

[0146] The first solid electrolyte material is manufactured, for example, by the following method.

[0147] Mix raw material powders in such a way as to have a target composition. Examples of the raw material powders are oxides, hydroxides, halides, or acyl halides.

[0148] As an example, when the target composition is LiNbOCl 4 LiCl and NbOCl are mixed as raw material powders in a molar ratio of 1:1. 3 .

[0149] The elements of M and X are determined by the selection of the raw material powders. The molar fractions of the elements constituting the first solid electrolyte material are determined by adjusting the molar ratio of the raw material powders and the synthesis process.

[0150] The raw material powders can be mixed in a molar ratio that is pre-adjusted in such a way as to offset possible compositional changes during the synthesis.

[0151] Mix the raw material powders to obtain a mixed powder. The mixed powder reacts with each other in a mixing device such as a planetary ball mill in a mechanochemical manner (i.e., by the method of mechanochemical grinding treatment) to obtain a reaction product. The reaction product can be fired in a vacuum or an inert gas atmosphere (such as argon or nitrogen). Alternatively, the mixed powder can also be sintered in a vacuum or an inert gas to obtain a reaction product. By these methods, the first solid electrolyte material is obtained.

[0152] The composition of the first solid electrolyte material can be determined using analytical methods such as inductively coupled plasma optical emission spectrometry (i.e., ICP optical emission spectrometry), ion chromatography, inert gas fusion-infrared absorption method, or EPMA (electron probe microanalysis) method. However, due to the low measurement accuracy, the oxygen content may have an error of about 10%.

[0153] <Method for manufacturing the second solid electrolyte material>

[0154] The second solid electrolyte material is manufactured, for example, using the following method.

[0155] Mix raw material powders in such a way as to have a target composition. Examples of the raw material powders are halides.

[0156] As an example, when the target composition is Li 3 YCl 4 LiCl and YCl are mixed as raw material powders in a molar ratio of 3:1. 3 .

[0157] By selecting the raw material powder, the elements constituting the second solid electrolyte material are determined. By adjusting the molar ratio of the raw material powder and the synthesis process, the molar fraction of the elements constituting the second solid electrolyte material is determined.

[0158] The raw material powders can be mixed in a molar ratio that is pre-adjusted in a manner that offsets possible compositional changes during synthesis.

[0159] The raw material powders are mixed to obtain a mixed powder. The mixed powder reacts with each other in a mixing device such as a planetary ball mill in a mechanochemical manner (i.e., by the method of mechanochemical grinding treatment) to obtain a reaction product. The reaction product can be fired in a vacuum or an inert gas atmosphere (such as an argon atmosphere or a nitrogen atmosphere). Alternatively, the mixed powder can also be sintered in a vacuum or an inert atmosphere to obtain a reaction product. By these methods, the second solid electrolyte material is obtained.

[0160] The composition of the second solid electrolyte material can be determined using analytical methods such as ICP emission spectrometry, ion chromatography, inert gas fusion-infrared absorption method, or EPMA method.

[0161] Examples

[0162] The present disclosure will be described in more detail with reference to the following examples.

[0163] Example 1

[0164] [Production of the first solid electrolyte material]

[0165] In a dry atmosphere having a dew point of -30°C or lower (hereinafter referred to as "dry atmosphere"), as raw material powders, Li 2 O 2 : TaCl 5 are prepared at a molar ratio of 1:2. Li 2 O 2 and TaCl 5 are obtained. These raw material powders are pulverized in a mortar to obtain a mixed powder. The obtained mixed powder is treated using a planetary ball mill (manufactured by Fritsch, model P-7) under the conditions of 24 hours and 600 rpm to cause a mechanochemical reaction. Then, the mixed powder is fired at 200°C for 6 hours. By operating in this way, the powder of the first solid electrolyte material of Example 1 is obtained. The first solid electrolyte material of Example 1 has a composition represented by Li 1.2 TaO 1.3 Cl 3.6 .

[0166] [Production of the second solid electrolyte material]

[0167] In a dry gas, as raw material powders, LiCl: YCL3 LiCl and YCl were prepared at a molar ratio of 3:1 3 . In addition, the second solid electrolyte material of Example 1 was obtained by operating in the same manner as the first solid electrolyte material of Example 1. The second solid electrolyte material of Example 1 has Li 3 YCl 6 represented composition.

[0168] [Measurement of Reduction Potentials of the First and Second Solid Electrolyte Materials]

[0169] The reduction potentials of the first and second solid electrolyte materials of Example 1 were measured by cyclic voltammetry. Specifically, the reduction potentials were measured by the following method.

[0170] In an insulating cylinder with an inner diameter of 9.5 mm, SUS foil, a solid electrolyte material (100 mg), and Li foil were stacked in sequence. A pressure of 360 MPa was applied to this stack. Then, current collectors made of stainless steel were installed above and below the stack, and current collector leads were installed on these current collectors. Finally, using an insulating ferrule, the inside of the insulating cylinder was isolated and sealed from the outside air. By operating in this way, a unit for potential measurement was obtained.

[0171] The unit for potential measurement was placed in a thermostat at 25°C. By cyclic voltammetry measurement, the potential was scanned at a scanning rate of 5 mV / second from -0.5 V to 6 V with respect to the Li reference potential.

[0172] As a result, the first solid electrolyte material of Example 1 has a reduction potential of 2.3 V. The second solid electrolyte material of Example 1 has a reduction potential of 0.3 V.

[0173] [Preparation of Electrolyte Mixture]

[0174] The first solid electrolyte material of Example 1 and the second solid electrolyte material of Example 1 were prepared at a mass ratio of 10:1. These materials were mixed in an agate mortar. By operating in this way, the electrolyte mixture of Example 1 was obtained.

[0175] [Fabrication of Positive Electrode Material]

[0176] In a dry atmosphere, the first solid electrolyte material of Example 1 and LiCoO 2 (hereinafter referred to as "LCO") were prepared at a volume ratio of 30:70. These materials were mixed in an agate mortar. By operating in this way, the positive electrode material of Example 1 was obtained.

[0177] [Fabrication of Battery]

[0178] In an insulating cylinder with an inner diameter of 9.5 mm, the positive electrode material (10 mg) of Example 1, the electrolyte mixture (80 mg) of Example 1, and the second solid electrolyte material (80 mg) of Example 1 were stacked in sequence to obtain a laminate. A pressure of 360 MPa was applied to this laminate to form a positive electrode, a first electrolyte layer, and a second electrolyte layer.

[0179] Next, aluminum powder (20 mg) was stacked on the positive electrode. A pressure of 360 MPa was applied to this laminate to form a positive electrode current collector.

[0180] Next, a metal In foil (thickness 200 μm), a metal Li foil (thickness 300 μm), and a metal In foil (thickness 200 μm) were stacked in sequence on the second electrolyte layer to obtain a laminate. A pressure of 80 MPa was applied to this laminate to form a negative electrode. A current collector made of stainless steel was disposed on the positive electrode current collector and the negative electrode, and a current collecting lead was installed on the current collector made of stainless steel.

[0181] Finally, an insulating collar was used to isolate the inside of the insulating cylinder from the outside air and seal the inside of the cylinder. By operating in this way, the battery of Example 1 was obtained.

[0182] Example 2

[0183] [Fabrication of the First Solid Electrolyte Material]

[0184] In a dry atmosphere, LiCl and NbOCl were prepared as raw material powders such that the 3 molar ratio became 1:1. 3 These raw material powders were pulverized in a mortar to obtain a mixed powder. The obtained mixed powder was processed using a planetary ball mill under the conditions of 24 hours and 600 rpm to cause a mechanochemical reaction. By operating in this way, the powder of the first solid electrolyte material of Example 2 was obtained. The first solid electrolyte material of Example 2 has a composition represented by 4 NbOCl.

[0185] [Measurement of the Reduction Potential of the First Solid Electrolyte Material]

[0186] The reduction potential of the first solid electrolyte material of Example 2 was measured by the same method as in Example 1. The first solid electrolyte material of Example 2 has a reduction potential of 2.9 V.

[0187] [Preparation of the Electrolyte Mixture]

[0188] Prepare the first solid electrolyte material of Example 2 and the second solid electrolyte material of Example 1 in a mass ratio of 10:2. These materials were mixed in an agate mortar. By operating in this way, the electrolyte mixture of Example 2 was obtained.

[0189] [Fabrication of the positive electrode material]

[0190] In a dry atmosphere, prepare the first solid electrolyte material of Example 2 and LCO in a mass ratio of 30:70. These materials were mixed in an agate mortar. By operating in this way, the positive electrode material of Example 2 was obtained.

[0191] [Fabrication of the battery]

[0192] Except for using the electrolyte mixture of Example 2 to replace the electrolyte mixture of Example 1, the battery of Example 2 was obtained by operating in the same manner as in Example 1.

[0193] Example 3

[0194] [Preparation of the electrolyte mixture]

[0195] Prepare the first solid electrolyte material of Example 1 and the second solid electrolyte material of Example 1 in a mass ratio of 10:5. These materials were mixed in an agate mortar. By operating in this way, the electrolyte mixture of Example 3 was obtained.

[0196] [Fabrication of the battery]

[0197] Except for using the electrolyte mixture of Example 3 to replace the electrolyte mixture of Example 1, the battery of Example 3 was obtained by operating in the same manner as in Example 1.

[0198] Example 4

[0199] [Fabrication of the second solid electrolyte material]

[0200] In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as "dry argon atmosphere"), as raw material powders, Li 2 S:P 2 S 5 Prepare Li 2 S and P 2 S 5。The raw material powders were pulverized in a mortar to obtain a mixed powder. Then, the obtained mixed powder was processed using a planetary ball mill under the conditions of 10 hours and 510 rpm to cause a mechanochemical reaction. By operating in this way, a glassy solid electrolyte was obtained. The obtained glassy solid electrolyte was heat-treated at 270 °C for 2 hours in a dry argon atmosphere. By operating in this way, a powder of a glass-ceramic solid electrolyte, i.e., the second solid electrolyte material of Example 4, was obtained. The second solid electrolyte material of Example 4 is composed of Li 2 S-P 2 S 5 represented glassy solid electrolyte.

[0201] [Measurement of Reduction Potential of the Second Solid Electrolyte Material]

[0202] The reduction potential of the second solid electrolyte material of Example 4 was measured by the same method as in Example 1. The second solid electrolyte material of Example 4 is stable to lithium.

[0203] [Preparation of Electrolyte Mixture]

[0204] The first solid electrolyte material of Example 1 and the second solid electrolyte material of Example 4 were prepared according to a mass ratio of 10:5. These materials were mixed in an agate mortar. By operating in this way, the electrolyte mixture of Example 4 was obtained.

[0205] [Fabrication of Battery]

[0206] A battery of Example 4 was obtained by operating in the same manner as in Example 1, except that the electrolyte mixture of Example 4 and the second solid electrolyte material of Example 4 were used instead of the electrolyte mixture of Example 1 and the second solid electrolyte material of Example 1.

[0207] Comparative Example 1

[0208] [Preparation of Electrolyte Mixture]

[0209] The first solid electrolyte material of Example 1 and the second solid electrolyte material of Example 1 were prepared according to a weight ratio of 10:0.5. These materials were mixed in an agate mortar. By operating in this way, the electrolyte mixture of Comparative Example 1 was obtained.

[0210] [Fabrication of Battery]

[0211] A battery of Comparative Example 1 was obtained by operating in the same manner as in Example 1, except that the electrolyte mixture of Comparative Example 1 was used instead of the electrolyte mixture of Example 1.

[0212] Comparative Example 2

[0213] [Fabrication of Battery]

[0214] A battery of Comparative Example 2 was obtained by operating in the same manner as in Example 1, except that the first solid electrolyte material of Example 1 was used instead of the electrolyte mixture of Example 1. That is, the first electrolyte layer of Comparative Example 2 contains only the first solid electrolyte material of Example 1 and does not contain the second solid electrolyte material.

[0215] [Charge and Discharge Test]

[0216] The charge and discharge tests of the batteries obtained from Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were carried out under the following conditions.

[0217] The obtained battery was placed in a thermostat at 25°C.

[0218] The battery was charged with a current value of 360 μA at a rate of 0.3C until a voltage of 4.2V was reached. Then, the battery was discharged with a current value of 360 μA at a rate of 0.3C until a voltage of 3.1V was reached.

[0219] The above charging and discharging were regarded as one charge and discharge cycle. The charge and discharge cycle was repeated 25 times.

[0220] The alloy formed by metal In and metal Li used for the negative electrode of the battery has a lithium potential of 0.6V.

[0221] Through the above charge and discharge tests, the discharge capacity retention rates of the batteries of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were calculated. The discharge capacity retention rate represents the ratio of the discharge capacity after 25 cycles to the initial discharge capacity. The values of the discharge capacity retention rate are shown in Table 1. In Table 1, the mass ratio of the second solid electrolyte material to the first solid electrolyte material in the first electrolyte layer is marked as the mass ratio of the electrolyte mixture.

[0222] Table 1

[0223]

[0224] "Examination"

[0225] As can be seen from Table 1, the batteries of Examples 1 to 4 have a high discharge capacity retention rate. That is, the batteries of Examples 1 to 4 have high cycle characteristics.

[0226] Comparing the batteries of Examples 1 and 3 with the batteries of Comparative Examples 1 and 2, it can be seen that the discharge capacity retention rate of the batteries with a mass ratio of the second solid electrolyte material to the first solid electrolyte material in the first electrolyte layer of 0.05 or less is low.

[0227] Comparing the batteries of Example 3 and Example 4 with each other, it can be seen that if the second solid electrolyte material is a sulfide solid electrolyte or a halide solid electrolyte, a battery with a high discharge capacity retention rate can be obtained.

[0228] Industrial applicability

[0229] The battery of the present disclosure can be used, for example, as an all-solid-state lithium ion secondary battery.

[0230] Symbol description

[0231] 1000 Battery

[0232] 101 Positive electrode

[0233] 102 First electrolyte layer

[0234] 103 Second electrolyte layer

[0235] 104 Negative electrode

Claims

1. A battery having a positive electrode, a first electrolyte layer, a second electrolyte layer, and a negative electrode in this order, wherein, the first electrolyte layer contains a first solid electrolyte material and a second solid electrolyte material, in the first electrolyte layer, the mass ratio of the second solid electrolyte material to the first solid electrolyte material is greater than 0.05 and less than 1, the second electrolyte layer contains the second solid electrolyte material, the first solid electrolyte material is formed of Li, M, O, and X, in the first solid electrolyte material, M is at least one element selected from metal elements and metalloid elements other than Li, and X is at least one element selected from Cl, Br, and I, and the second solid electrolyte material has a composition different from that of the first solid electrolyte material, the first solid electrolyte material is represented by the following chemical formula (1), Li α MO β X γ (1) wherein the following mathematical formulas 1.0 ≤ α ≤ 1.2, 1.0 ≤ β ≤ 1.3, and 3.6 ≤ γ ≤ 4.0 are satisfied, M contains at least one element selected from Nb and Ta, the second solid electrolyte material is a halide solid electrolyte other than the oxyhalide solid electrolyte of the first solid electrolyte material, or a sulfide solid electrolyte containing lithium sulfide and phosphorus sulfide, the halide solid electrolyte is formed of Li, M', and X', where M' is at least one element selected from metal elements and metalloid elements other than Li, and M' contains yttrium, X' is at least one element selected from Cl, Br, and I.

2. The battery according to claim 1, wherein, the reduction potential of the second solid electrolyte material is lower than the reduction potential of the first solid electrolyte material.

3. The battery according to claim 1 or 2, wherein, the mass ratio is greater than 0.05 and 0.50 or less.

4. The battery according to claim 3, wherein, the mass ratio is 0.10 to 0.

50.

5. The battery according to claim 1 or 2, wherein, the mathematical formula: γ = 5 + α - 2β is satisfied.

6. The battery according to claim 1 or 2, wherein, the halide solid electrolyte is represented by the following chemical formula (2), Li 6-3z Y z X’ 6 (2) wherein the mathematical formula: 0 < z < 2 is satisfied.

7. The battery according to claim 6, wherein, The halide solid electrolyte is Li 3 YCl 6 .

8. The battery according to claim 1 or 2, wherein, The sulfide solid electrolyte is Li 2 S-P 2 S 5 .

9. The battery according to claim 1 or 2, wherein, the positive electrode contains the first solid electrolyte material.

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