Negative electrode for all-solid-state battery, and all-solid-state battery

Abstract

This negative electrode for an all-solid-state battery comprises an active material, a carbon material, and a solid electrolyte, wherein: the solid electrolyte is represented by (1) LiaEbGcXd, where X is Cl or Cl and at least one element selected from the group consisting of F, Br, and I; and the D / G ratio of the carbon material satisfies 0-1.10, the D / G ratio being an intensity ratio obtained by dividing the peak intensity of a D-band peak occurring in the vicinity of 1360 cm-1 in a Raman spectrum measured by Raman spectroscopy, by the peak intensity of a G-band peak occurring in the vicinity of 1600 cm-1 in the Raman spectrum.

Description

Anode for all-solid-state battery and all-solid-state battery

[0001] The present invention relates to a negative electrode for an all-solid-state battery and an all-solid-state battery. This application claims priority based on Japanese Patent Application No. 2024-007135, filed on January 22, 2024, the contents of which are incorporated herein by reference.

[0002] With the remarkable development of electronics technology, portable electronic devices are becoming smaller, lighter, thinner, and more multifunctional. There is also a strong demand for batteries, which serve as the power source for electronic devices, to be smaller, lighter, thinner, more reliable, and safer. All-solid-state batteries, which use solid electrolytes, are attracting attention because they are safer than lithium-ion secondary batteries, which use liquid electrolytes.

[0003] The solid electrolyte may be an oxide-based solid electrolyte, a sulfide-based solid electrolyte, a complex hydride-based solid electrolyte, a halide-based solid electrolyte, or the like. ２＋ａ E １-ｂ+α G ｂ D ｃ X ｄ The halide-based solid electrolyte has higher atmospheric stability, higher high-voltage resistance, and is more adaptable to various processes than oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, etc.

[0004] Carbon materials are sometimes used as active materials or conductive additives in electrodes of all-solid-state batteries. For example, Patent Document 2 discloses the use of a carbon material having a lattice spacing within a predetermined range as an active material for all-solid-state batteries. Furthermore, Patent Document 3 discloses the use of a carbon material having a predetermined X-ray diffraction spectrum (X-ray diffraction pattern, XRD pattern) as a conductive additive.

[0005] International Publication No. 2021 / 024785 International Publication No. 2022 / 138753 International Publication No. 2019 / 026940

[0006] Halide-based solid electrolytes are prone to reductive decomposition. In all-solid-state batteries using halide-based solid electrolytes, LiCl may be generated as a by-product between the solid electrolyte and the conductive additive. It is believed that LiCl is generated when the solid electrolyte reacts with the conductive additive due to potential changes in the solid electrolyte, annealing, or the like. This by-product is generated by the decomposition of the solid electrolyte. The decomposition of the solid electrolyte is an irreversible reaction, and is one of the causes of a decrease in the charge / discharge efficiency of all-solid-state batteries.

[0007] The present disclosure has been made in view of the above problems, and aims to provide a negative electrode for an all-solid-state battery and an all-solid-state battery that suppresses irreversible reactions in a solid electrolyte and has high charge / discharge efficiency.

[0008] In order to solve the above problems, the following means are provided.

[0009] The negative electrode for an all-solid-state battery according to the first aspect includes an active material, a carbon material, and a solid electrolyte. ａ E ｂ G ｃ X ｄ In formula (1), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids, and G is OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO ４ , Si ２ O ７ , Si ３ O ９ , Si ４ O １１ , Si ６ O １８ , P.O. ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３, S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , B.F. ４ , P.F. ６ ,BOB,(COO) ２ , N, AlCl ４ , C.F. ３ SO ３ , C.H. ３ COO, CF ３ COO,OOC-(CH ２ ) ２ -COO, OOC-CH ２ -COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH ２ -COO, C ６ H ５ SO ３ , OOC-CH=CH-COO, C(OH)(CH ２ COOH) ２ COO, AsO ４ , Bio ４ , CrO ４ , MnO ４ , PtF ６ , PtCl ６ , PtBr ６ , PtI ６ , SbO ４ , SeO ４ , TeO ４ , HCOO, and O, X is Cl or at least one element selected from the group consisting of Cl and F, Br, and I, a satisfies 0.5≦a<6, b satisfies 0<b<2, c satisfies 0≦c≦6, and d satisfies 0<d≦6.1. The D / G ratio of the carbon material satisfies 0 or more and 1.10 or less. The D / G ratio is measured by Raman spectroscopy using a Raman spectrum of 1360 cm －１ The peak intensity of the D band peak occurring near 1600 cm －１This is the intensity ratio obtained by dividing the peak intensity by the peak intensity of the G band peak occurring nearby.

[0010] In the negative electrode for an all-solid-state battery according to the above aspect, the diffraction peak attributable to the (002) plane in the diffraction spectrum obtained by measuring the carbon material by an X-ray diffraction method may have a half-width of 0.1° or more and 2.0° or less.

[0011] In the negative electrode for an all-solid-state battery according to the above embodiment, in the formula (1), E is Al or Zr, and G is PO ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , O, and X may be Cl.

[0012] In the negative electrode for an all-solid-state battery according to the above aspect, the active material may include a carbon material selected from the group consisting of natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, and a fired organic compound; a metal, alloy, or composite material capable of reacting with lithium; an oxide; or metallic lithium.

[0013] An all-solid-state battery according to a second aspect includes the all-solid-state battery negative electrode according to the above aspect.

[0014] The negative electrode for an all-solid-state battery according to the above embodiment is less likely to cause irreversible reactions in the solid electrolyte, and has high charge / discharge efficiency.

[0015] 1 is a cross-sectional view of an all-solid-state battery according to an embodiment of the present invention;

[0016] The present embodiment will be described in detail below with reference to the accompanying drawings. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional proportions of each component may differ from the actual proportions. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate modifications can be made within the scope of the present invention.

[0017] "All-Solid-State Battery" FIG. 1 is a cross-sectional schematic diagram of an all-solid-state battery 100 according to this embodiment. The all-solid-state battery 100 shown in FIG. 1 includes a power generating element 40 and an exterior body 50. The exterior body 50 covers the periphery of the power generating element 40. The power generating element 40 is connected to the outside via a pair of terminals 60, 62 connected to the power generating element 40. Although a stacked-type battery is shown in FIG. 1, a wound-type battery may also be used. The all-solid-state battery 100 is used, for example, in laminated batteries, prismatic batteries, cylindrical batteries, coin batteries, button batteries, etc.

[0018] <Power generating element> The power generating element 40 includes a solid electrolyte layer 10, a positive electrode 20, and a negative electrode 30. The power generating element 40 is charged or discharged by the exchange of ions between the positive electrode 20 and the negative electrode 30 via the solid electrolyte layer 10 and the exchange of electrons via an external circuit.

[0019] 1, the negative electrode 30 has a negative electrode current collector 32 and a negative electrode active material layer 34. The negative electrode active material layer 34 is in contact with the negative electrode current collector 32. The negative electrode active material layer 34 is located between the negative electrode current collector 32 and the solid electrolyte layer 10. The negative electrode 30 may be a single layer in which the material constituting the negative electrode current collector 32 and the material constituting the negative electrode active material layer 34 are mixed.

[0020] The negative electrode current collector 32 has electronic conductivity. The negative electrode current collector 32 is made of, for example, a metal such as copper, aluminum, nickel, stainless steel, or iron, or a conductive resin. The negative electrode current collector 32 may be in the form of a powder, a foil, a punched piece, or an expanded piece.

[0021] The negative electrode active material layer 34 includes a negative electrode active material, a solid electrolyte, and a conductive additive. The negative electrode active material layer 34 may also include a binder.

[0022] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions, and insert and extract lithium ions. The negative electrode active material can be any negative electrode active material used in known all-solid-state batteries. Examples of the negative electrode active material include carbon materials, metals, alloys, or composite materials that can combine with lithium, oxides, and metallic lithium. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, and organic compound sintered bodies. Si, SiO ｘ , Sn, and aluminum are examples of metals that can combine with lithium. Composite materials are composites of these metals and carbon materials. Lithium titanate (Li ４ Ti ５ O １２ ), SnO ２ is an example of an oxide.

[0023] When the negative electrode active material is a carbon material and the conductive additive is also a carbon material, they can be distinguished by analyzing them using micro-Raman spectroscopy. For example, an area with a side length of 50 μm is measured using micro-Raman spectroscopy, and a Raman mapping classified by the crystallinity of the carbon material is obtained from the Raman spectrum. Because the carbon material functioning as the negative electrode active material and the carbon material functioning as the conductive additive have different crystallinity, the respective carbon materials are classified as different regions. In the negative electrode active material layer 34, the abundance ratio of the negative electrode active material is higher than the abundance ratio of the conductive additive. Therefore, among the multiple regions classified as carbon materials, the region with a high volume ratio can be determined to be carbon material derived from the negative electrode active material, and the region with a low volume ratio can be determined to be carbon material derived from the conductive additive.

[0024] The median diameter of the negative electrode active material is, for example, 0.7 μm or more and 30 μm or less. When the negative electrode active material and the conductive additive are carbon materials, they can also be roughly distinguished from each other based on the median diameter.

[0025] The solid electrolyte is, for example, a halide-based solid electrolyte containing Cl. The solid electrolyte contained in the negative electrode 30 is a conduction path for lithium ions within the negative electrode.

[0026] The solid electrolyte is Liａ E ｂ G ｃ X ｄ ... is expressed as (1).

[0027] In formula (1), a represents the composition ratio of Li in the compound represented by formula (1). In formula (1), a satisfies 0.5≦a<6.0. When E is Al, Sc, Y, or a lanthanide, a preferably satisfies 2.0≦a≦4.0, and more preferably satisfies 2.5≦a≦3.5. When E is Zr or Hf, a preferably satisfies 1.0≦a≦3.0, and more preferably satisfies 1.5≦a≦2.5. In the solid electrolyte represented by formula (1), when a satisfies 0.5≦a<6.0, the content of Li contained in the compound becomes appropriate, and the ionic conductivity of the solid electrolyte is increased.

[0028] In formula (1), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids. E is an element that forms the skeleton of the halide-based solid electrolyte represented by formula (1). Lanthanoids are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A solid electrolyte containing E has a wide potential window and high ionic conductivity. E is more preferably any of Al, Sc, Y, Zr, Hf, and La, and even more preferably Al or Zr.

[0029] In formula (1), b is the composition ratio of E in the compound represented by formula (1). b satisfies 0<b<2.0, and more preferably satisfies 0.6≦b. b may also satisfy b≦1.0. E is an element having a higher density than the other elements contained in formula (1). An all-solid-state battery containing a solid electrolyte that satisfies b≦1.0 has a low solid electrolyte density and a high capacity.

[0030] In formula (1), G is substituted with a part of E that forms the framework of the solid electrolyte. The compound of formula (1) may not contain G. G is, for example, OH, BO ２ , B.O. ３ , B.O. ４ , B ３ O ６ , B４ O ７ 、CO ３ 、NO ３ 、AlO ２ 、SiO ３ 、SiO ４ 、Si ２ O ７ 、Si ３ O ９ 、Si ４ O １１ 、Si ６ O １８ 、PO ３ 、PO ４ 、P ２ O ７ 、P ３ O １０ 、SO ３ 、SO ４ 、SO ５ 、S ２ O ３ 、S ２ O ４ 、S ２ O ５ 、S ２ O ６ 、S ２ O ７ 、S ２ O ８ 、BF ４ 、PF ６ 、BOB、(COO) ２ 、N、AlCl ４ 、CF ３ SO ３ 、CH ３ COO、CF ３ COO、OOC-(CH ２ ) ２ -COO、OOC-CH ２ -COO、OOC-CH(OH)-CH(OH)-COO、OOC-CH(OH)-CH ２ -COO、C ６ H ５ SO ３ 、OOC-CH=CH-COO、C(OH)(CH ２ COOH) ２ COO、AsO ４ 、BiO ４ 、CrO ４ 、MnO ４ 、PtF ６ 、PtCl６ , PtBr ６ , PtI ６ , SbO ４ , SeO ４ , TeO ４ , HCOO, and O. G is at least one group selected from the group consisting of PO ３ , P.O. ４ , P ２ O ７ , P ３ O １０ , S.O. ３ , S.O. ４ , S.O. ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , and O. These groups have a strong covalent bond with E. Therefore, when G is contained, E ions are less likely to be reduced, and the solid electrolyte is less likely to be reductively decomposed. A solid electrolyte containing G has a wide potential window on the reduction side and is less likely to be reduced.

[0031] In formula (1), c represents the composition ratio of G in the compound represented by formula (1). c is 0≦c≦6.0, preferably 0.1≦c, and more preferably 0.5≦c. A solid electrolyte containing G in this range has a wide potential window on the reduction side and is less susceptible to reductive decomposition. Furthermore, c is preferably c≦3.0. If the G content is high, the ionic conductivity of the solid electrolyte decreases.

[0032] In formula (1), X is a halide atom. X is an essential atom of the solid electrolyte. X includes Cl. X is preferably Cl. X may include at least one element selected from the group consisting of F, Br, and I together with Cl. X has a large ionic radius per valence. By including X, the halide-based solid electrolyte represented by formula (1) allows lithium ions to flow easily and has high ionic conductivity. Furthermore, by including Cl as X, the halide-based solid electrolyte represented by formula (1) has high ionic conductivity and excellent oxidation resistance and reduction resistance.

[0033] In formula (1), d represents the composition ratio of X in the compound represented by formula (1). d satisfies 0<d≦6.1. d preferably satisfies 1.0≦d. When d satisfies 1.0≦d, the strength of the pellet increases when the solid electrolyte is pressure-molded into a pellet. Furthermore, when d satisfies 1.0≦d, the ionic conductivity of the solid electrolyte increases. Furthermore, d preferably satisfies d≦5.0. This is to avoid a situation where an increase in the content of X leads to a shortage of G and a narrowing of the potential window of the solid electrolyte.

[0034] The halide-based solid electrolyte represented by formula (1) is, for example, Li ２ ZrCl ６ , Li ２ ZrSO ４ Cl ４ , Li ２ ZrPO ３ Cl ４ , Li ２ ZrCO ３ Cl ４ , Li ２ Zr((COO) ２ ) ０．５ Cl ５ , Li ２ Zr(CH ３ COO) ０．２ Cl ５．８ , Li ２ Zr(CF ３ COO) ０．２ Cl ５．８ , Li ２ Zr(HCOO) ０．４ Cl ５．６ , Li ２ZrBO ２ Cl ５ , Li ２ ZrBF ４ Cl ５ , Li ３ YSO ４ Cl ４ , Li ３ YCO ３ Cl ４ , Li ３ YBO ２ Cl ５ , Li ３ YBF ４ Cl ５ , Li ２ ZrOCl ４ is.

[0035] The content of the solid electrolyte in the negative electrode active material layer 34 is not particularly limited, but is preferably 1 mass % or more and 50 mass % or less, and more preferably 5 mass % or more and 30 mass % or less, based on the total mass of the negative electrode active material, the solid electrolyte, the conductive additive, and the binder.

[0036] The conductive additive is a carbon material, such as carbon black, acetylene black, ketjen black, graphite, carbon nanotubes, graphene, etc. The conductive additive improves the electronic conductivity of the negative electrode active material layer 34.

[0037] The D / G ratio of the carbon material used in the conductive additive satisfies 0 or more and 1.10 or less, preferably 0.05 or more and 1.0 or less. The D / G ratio is measured by Raman spectroscopy using a Raman spectrum of 1360 cm －１ The peak intensity of the D band peak occurring near 1600 cm －１ It is an intensity ratio obtained by dividing the G band peak intensity by the G band peak intensity that occurs nearby. The G band peak is a peak derived from the movement of carbon atoms within a hexagonal lattice. The D band peak is a peak derived from graphite defects. The lower the D / G ratio, the higher the crystallinity of the carbon material.

[0038] The Raman spectrum can be determined by laser Raman spectroscopy. For example, the Raman spectrum is measured using an NRS-7100 (manufactured by JASCO Corporation). The measurement conditions are a central wave number of 1700.14 cm －１ , 291.137cm －１ ~2900.14cm －１ The measurement range is 100 μm, excitation wavelength is 532.15 nm, grating is 600 l / m, slit width is 25 × 1000 μm, aperture is φ40 μm, objective lens is MPLFLN20×, laser intensity is 2.3 mW, and the OD of the attenuator is 0.6. Each peak intensity is calculated as the average value of three or more measurements of the Raman spectrum.

[0039] The half-width of the diffraction peak attributable to the (002) plane in the diffraction spectrum (X-ray diffraction pattern, XRD pattern) of the carbon material used in the conductive additive is preferably 0.1° or more and 2.0° or less. The diffraction spectrum is an X-ray diffraction spectrum measured by X-ray diffraction using Cu-Kα radiation. The half-width of the diffraction peak attributable to the (002) plane is one of the indicators indicating the degree of disorder in the crystalline structure of the carbon material. When the half-width of the diffraction peak attributable to the (002) plane satisfies the above range, the conductive additive has high crystallinity and is less likely to react with the solid electrolyte.

[0040] The median diameter of the conductive additive is, for example, 0.02 μm or more and 40 μm or less. The content of the conductive additive in the negative electrode active material layer 34 is not particularly limited. For example, based on the total mass of the negative electrode active material, solid electrolyte, conductive additive, and binder, the mass ratio of the conductive additive is preferably 0.5 mass% or more and 20 mass% or less, and more preferably 1 mass% or more and 5 mass% or less.

[0041] The negative electrode active material layer 34 may contain a binder. The binder bonds the negative electrode active material, the solid electrolyte material, and the conductive additive to one another within the negative electrode active material layer 34, and also firmly bonds the negative electrode active material layer 34 to the negative electrode current collector 32. The negative electrode active material layer 34 preferably contains a binder. The binder preferably has oxidation resistance and good adhesiveness.

[0042] Examples of binders that can be used in the negative electrode active material layer 34 include polyvinylidene fluoride (PVDF) or copolymers thereof, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole (PBI), polyethersulfone (PES), polyacrylic acid (PA) and copolymers thereof, metal ion crosslinked polyacrylic acid (PA) and copolymers thereof, maleic anhydride-grafted polypropylene (PP), maleic anhydride-grafted polyethylene (PE), and mixtures thereof. Among these, PVDF is particularly preferably used as the binder.

[0043] The binder content in the negative electrode active material layer 34 is not particularly limited, but is preferably 0.3% by mass to 10% by mass, and more preferably 0.3% by mass to 5% by mass, based on the total mass of the negative electrode active material, solid electrolyte, conductive additive, and binder. If the binder content is too low, it tends to be difficult to form a negative electrode 30 with sufficient adhesive strength. Conversely, if the binder content is too high, typical binders are electrochemically inactive and do not contribute to discharge capacity, making it difficult to obtain sufficient volume or mass energy density. It can also be said that the remainder of the negative electrode active material layer 34, other than the solid electrolyte, conductive additive (carbon material), and binder, is the negative electrode active material.

[0044] 1, the positive electrode 20 has a plate-shaped (foil-shaped) positive electrode current collector 22 and a positive electrode active material layer 24. The positive electrode active material layer 24 is in contact with at least one surface of the positive electrode current collector 22.

[0045] The positive electrode current collector 22 may be made of any electronically conductive material that is resistant to oxidation during charging and corrosion. The positive electrode current collector 22 may be made of, for example, a metal such as aluminum, stainless steel, nickel, or titanium, or a conductive resin. The positive electrode current collector 22 may be in the form of a powder, foil, punched, or expanded.

[0046] The positive electrode active material layer 24 contains a positive electrode active material, and optionally a solid electrolyte, a binder, and a conductive additive.

[0047] The positive electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions and insert and extract them (intercalate and deintercalate), and any positive electrode active material used in known all-solid-state batteries can be used. Examples of the positive electrode active material include lithium-containing metal oxides and lithium-containing metal phosphates.

[0048] The lithium-containing metal oxide is, for example, lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), lithium manganese spinel (LiMn ２ O ４ ), and the general formula: LiNi ｘ Co ｙ Mn ｚ O ２ A composite metal oxide represented by (x + y + z = 1), a lithium vanadium compound (LiVOPO ４ , Li ３ V ２ (P.O. ４ ) ３ ), olivine-type LiMPO ４ (wherein M represents at least one selected from Co, Ni, Mn, and Fe), lithium titanate (Li ４ Ti ５ O １２ ) etc.

[0049] The positive electrode active material may not contain lithium. Examples of such a positive electrode active material include lithium-free metal oxides (MnO ２ , V ２ O ５ etc.), lithium-free metal sulfides (MoS ２ etc.), lithium-free fluorides (FeF ３ , V.F. ３ When a positive electrode active material that does not contain lithium is used, the negative electrode is doped with lithium ions in advance, or a negative electrode containing lithium ions is used.

[0050] The positive electrode active material layer 24 may contain a solid electrolyte. The solid electrolyte may be, for example, the solid electrolyte described above. Alternatively, the solid electrolyte contained in the positive electrode active material layer may be a known solid electrolyte different from the solid electrolyte described above.

[0051] The content of the solid electrolyte in the positive electrode active material layer 24 is not particularly limited, but is preferably 1 mass % or more and 50 mass % or less, and more preferably 5 mass % or more and 30 mass % or less, based on the total mass of the positive electrode active material, the solid electrolyte, the conductive additive, and the binder.

[0052] The positive electrode active material layer 24 may contain a binder. The binder bonds the positive electrode active material, the solid electrolyte material, and the conductive additive to one another within the positive electrode active material layer 24, and also firmly bonds the positive electrode active material layer 24 to the positive electrode current collector 22. The positive electrode active material layer 24 preferably contains a binder. The binder preferably has oxidation resistance and good adhesiveness. The binder contained in the positive electrode active material layer 24 is the same as the binder contained in the negative electrode 30.

[0053] The positive electrode active material layer 24 may contain a conductive additive. The conductive additive improves the electronic conductivity of the positive electrode active material layer 24. The conductive additive may be the same as or different from the conductive additive used in the negative electrode active material layer 34. Examples of the conductive additive include carbon materials such as carbon black, graphite, carbon nanotubes, and graphene; metals such as aluminum, copper, nickel, stainless steel, iron, and amorphous metals; conductive oxides such as ITO; and mixtures thereof. The conductive additive may be in the form of powder or fiber.

[0054] There are no particular limitations on the content of the conductive additive in the positive electrode active material layer 24. When a conductive additive is added, the mass ratio of the conductive additive is preferably 0.5 mass % or more and 20 mass % or less, and more preferably 1 mass % or more and 5 mass % or less, based on the total mass of the positive electrode active material, solid electrolyte, conductive additive, and binder.

[0055] (Solid Electrolyte Layer) The solid electrolyte layer 10 is sandwiched between the positive electrode 20 and the negative electrode 30. The solid electrolyte layer 10 includes a solid electrolyte that can transfer ions by an externally applied voltage. For example, the solid electrolyte conducts lithium ions and inhibits the transfer of electrons.

[0056] The solid electrolyte layer 10 is, for example, a halide-based solid electrolyte. The solid electrolyte layer 10 includes, for example, the above-mentioned solid electrolyte. The solid electrolyte included in the solid electrolyte layer 10 may be different from the above-mentioned solid electrolyte.

[0057] The solid electrolyte layer 10 may contain a binder in addition to the solid electrolyte. The binder may be the same as that used in the positive electrode 20 or the negative electrode 30.

[0058] <Exterior Body> The exterior body 50 houses the power generating element 40 inside. The exterior body 50 prevents moisture and the like from entering from the outside to the inside. As shown in Fig. 1 , the exterior body 50 has a metal foil 52 and a resin layer 54 laminated on each side of the metal foil 52. The exterior body 50 is a metal laminate film in which the metal foil 52 is coated with the resin layer 54 from both sides.

[0059] The metal foil 52 is, for example, aluminum foil or stainless steel foil. The resin layer 54 can be, for example, a resin film such as polypropylene. The materials constituting the inner and outer resin layers 54 may be different. For example, the outer material can be a polymer with a high melting point, such as polyethylene terephthalate (PET) or polyamide (PA), and the inner material can be polyethylene (PE) or polypropylene (PP).

[0060] <Terminals> The terminals 60 and 62 are connected to the negative electrode 30 and the positive electrode 20, respectively. The terminal 62 connected to the positive electrode 20 is a positive electrode terminal, and the terminal 60 connected to the negative electrode 30 is a negative electrode terminal. The terminals 60 and 62 are responsible for electrical connection to the outside. The terminals 60 and 62 are made of a conductive material such as aluminum, nickel, or copper. The connection method may be welding or screw fastening. It is preferable to protect the terminals 60 and 62 with insulating tape to prevent short circuits.

[0061] [Method for manufacturing all-solid-state battery] The positive electrode 20 is manufactured by applying a paste containing a positive electrode active material onto the positive electrode current collector 22 and drying it to form a positive electrode active material layer 24. The above-mentioned solid electrolyte and the above-mentioned conductive additive may be added to the paste containing the positive electrode active material.

[0062] Next, the negative electrode 30 is prepared. A paste containing a negative electrode active material is applied to a negative electrode current collector 32 and dried to form a negative electrode active material layer 34, thereby manufacturing the negative electrode 30. The above-described solid electrolyte and the above-described conductive additive are added to the paste containing the negative electrode active material. The above-described conductive additive is obtained by analyzing commercially available carbon materials by Raman spectroscopy and selecting those that satisfy a predetermined D / G ratio.

[0063] The power generating element 40 can be produced, for example, by powder molding. A guide with a hole is placed on the positive electrode 20, and the guide is filled with a solid electrolyte. The surface of the solid electrolyte is then smoothed, and the negative electrode 30 is placed on top of the solid electrolyte. This sandwiches the solid electrolyte between the positive electrode 20 and the negative electrode 30. Pressure is then applied to the positive electrode 20 and the negative electrode 30 to pressure-molde the solid electrolyte. This pressure molding produces a laminate in which the positive electrode 20, solid electrolyte layer 10, and negative electrode 30 are stacked in this order.

[0064] Next, external terminals are welded to the positive electrode current collector 22 of the positive electrode 20 and the negative electrode current collector 32 of the negative electrode 30, which form the laminate, by a known method, to electrically connect the positive electrode current collector 22 or the negative electrode current collector 32 to the external terminals. Thereafter, the laminate connected to the external terminals is housed in an exterior body 50, and the opening of the exterior body 50 is hermetically sealed by heat sealing. Through the above steps, the all-solid-state battery 100 of this embodiment is obtained.

[0065] The all-solid-state battery 100 according to this embodiment has high charge-discharge efficiency. This is thought to be because the solid electrolyte according to this embodiment is not susceptible to reductive decomposition. The reductive decomposition of the solid electrolyte is an irreversible reaction, and the decomposed solid electrolyte loses its function as a solid electrolyte. Therefore, when the solid electrolyte is reductively decomposed, the charge-discharge efficiency of the all-solid-state battery decreases.

[0066] In the negative electrode after the electrochemical reaction and heat treatment, LiCl may be generated as a by-product between the solid electrolyte and the conductive additive. LiCl is thought to be generated as a result of a reaction between functional groups on the surface of the conductive additive and the solid electrolyte. LiCl is one of the stable phases that occurs when functional groups on the surface of the conductive additive react with the solid electrolyte. The conductive additive according to this embodiment has a low D / G ratio and high crystallinity, and therefore does not contain many functional groups on its surface. Therefore, it is thought that the reaction between the functional groups on the surface of the conductive additive and the solid electrolyte is suppressed, and the reductive decomposition of the solid electrolyte is suppressed.

[0067] Halide-based solid electrolytes are less stable to Li and more susceptible to reductive decomposition than oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, etc. Even when a halide-based solid electrolyte is used, the reductive decomposition of the solid electrolyte can be suppressed by controlling the D / G ratio of the conductive additive.

[0068] The above describes the embodiments of the present invention in detail with reference to the drawings. However, each configuration and combination thereof in each embodiment is merely an example, and addition, omission, substitution, and other modifications of the configuration are possible within the scope that does not deviate from the requirements of the present invention.

[0069] Example 1 In Example 1, a charge / discharge half-cell was fabricated and the charge / discharge efficiency was measured. The charge / discharge half-cell of Example 1 was fabricated in the following manner.

[0070] The charge / discharge half-cell was fabricated in a glove box with argon gas circulating at a dew point of approximately -70°C. A lower punch was inserted into a PEEK cylinder of a pellet fabrication jig, and a solid electrolyte Li was placed on top of the lower punch. ２ Zr(SO ４ ) Cl ４ 110 mg of was added.

[0071] The pelletizing jig had a PEEK (polyether ether ketone) cylinder with an outer diameter of 30 mm, an inner diameter of 10 mm, and a height of 20 mm, and upper and lower punches with a diameter of 9.99 mm. The upper and lower punches were made of die steel (SKD11 material).

[0072] The solid electrolyte was prepared by the following procedure. In a glove box filled with an Ar gas atmosphere, lithium sulfate (Li ２ SO ４ ) and zirconium chloride (ZrCl ４ ) were weighed out so that the molar ratio was 1:1. The raw material powder was placed in a zirconia sealed container for a planetary ball mill, which had already contained zirconia balls. Next, a lid was placed on the sealed container, and the lid was screwed onto the container body. The space between the lid and the container was sealed with polyimide tape. The polyimide tape has the effect of blocking moisture. Next, the zirconia sealed container was set in the planetary ball mill. The raw material powder was subjected to a mechanochemical reaction for 24 hours under conditions of a rotation speed of 500 rpm and a revolution speed of 500 rpm (the rotation direction and the revolution direction were opposite).

[0073] The PEEK cylinder was then vibrated to smooth the surface of the solid electrolyte, after which an upper punch was inserted onto the solid electrolyte and pressed with a press under a load of 373 MPa to form a solid electrolyte layer.

[0074] Next, the upper punch was removed, and 15 mg of a negative electrode mixture was placed on the solid electrolyte layer. The negative electrode mixture contained a negative electrode active material, the above-mentioned solid electrolyte, and a conductive additive in a ratio of negative electrode active material:solid electrolyte:conductive additive = 70 wt %:25 wt %:5 wt %. The negative electrode mixture was obtained by mixing these raw materials in an agate mortar for 15 minutes. The negative electrode active material was lithium titanate (Li ４ Ti ５ O １２ The conductive additive was a carbon material having a D / G ratio of 0.3 and an XRD pattern with a half-width of the diffraction peak attributable to the (002) plane of 1.1°.

[0075] Next, the PEEK cylinder was vibrated to level the surface of the negative electrode mixture. Then, an upper punch was inserted onto the negative electrode mixture and pressed with a press under a load of 373 MPa. Next, the lower punch was removed, and a lithium foil with a diameter of 10 mm and a thickness of 100 μm was placed on the solid electrolyte layer, and the lower punch was inserted. The half cell was configured as a negative electrode mixture layer / solid electrolyte layer / Li foil.

[0076] Two stainless steel plates with a diameter of 50 mm and a thickness of 5 mm and two Bakelite® plates with a diameter of 50 mm and a thickness of 2 mm were also prepared. Four screw holes were then formed in each of the two stainless steel plates and the two Bakelite® plates. The screw holes were positioned so that when the half-cell, the two stainless steel plates, and the two Bakelite® plates were stacked, the two stainless steel plates and the two Bakelite® plates would overlap in plan view, but would not overlap with the half-cell in plan view.

[0077] Next, a stainless steel plate, a Bakelite® plate, a half cell, a Bakelite® plate, and a stainless steel plate were stacked in this order, and screws were inserted into the screw holes and tightened with a torque of 1 N m. In this way, a half cell was obtained in which the upper and lower punches of the electrochemical cell were insulated by the Bakelite® plate. Next, the half cell was left to stand in a thermostatic bath at 25°C for 48 hours to stabilize the open circuit voltage.

[0078] The half cell of Example 1 was charged and discharged under the following conditions to measure the initial charge-discharge efficiency. Measurements of charge and discharge, charge capacity, and discharge capacity in the charge-discharge test were performed using a charge-discharge device BCS805 (trade name; manufactured by Biologic).

[0079] The initial charge-discharge efficiency was calculated using the charge capacity in the first cycle (initial charge capacity) and the discharge capacity in the first cycle (initial discharge capacity) according to the following formula: Initial charge-discharge efficiency (%) = (discharge capacity in the first cycle (mAh) / charge capacity in the first cycle (mAh)) × 100

[0080] The charge / discharge test was performed at 1 V (vs. Li / Li ＋ ) and discharged to 3V (vs. Li / Li ＋ The charge rate and discharge rate were 0.05 C (a current value at which charging or discharging is completed in 20 hours when charging or discharging at a constant current of 1 mA is performed at 25° C.).

[0081] Examples 2 to 7 Examples 2 to 7 differ from Example 1 in that the conductive additive contained in the negative electrode composite was changed. Other conditions in Examples 2 to 7 were the same as in Example 1. The D / G ratios of the carbon materials used as conductive additives in Examples 2 to 7 and the half-value widths of the diffraction peaks attributable to the (002) plane in the XRD patterns are shown below. Example 2: D / G ratio 0.8, (002) peak half width 0.6° Example 3: D / G ratio 0.1, (002) peak half width 0.5° Example 4: D / G ratio 1.1, (002) peak half width 4.1° Example 5: D / G ratio 1.1, (002) peak half width 1.7° Example 6: D / G ratio 0.9, (002) peak half width 2.0° Example 7: D / G ratio 0.6, (002) peak half width 1.9°

[0082] In Examples 2 to 7, the charge-discharge characteristics were measured in the same manner as in Example 1.

[0083] Comparative Examples 1 to 3 Comparative Examples 1 to 3 differ from Example 1 in that the conductive additive contained in the negative electrode composite was changed. Other conditions in Comparative Example 1 were the same as those in Example 1. The D / G ratios of the carbon materials used as conductive additives in Comparative Examples 1 to 3 and the half widths of the diffraction peaks attributable to the (002) plane in the XRD patterns are shown below. Comparative Example 1: D / G ratio 1.2, (002) peak half width 4.7° Comparative Example 2: D / G ratio 1.2, (002) peak half width 2.9° Comparative Example 3: D / G ratio 1.5, (002) peak half width 2.8°

[0084] Comparative Examples 4 and 5 Comparative Examples 4 and 5 differ from Example 1 in that the solid electrolyte contained in the solid electrolyte layer and the negative electrode composite was changed, and the conductive additive contained in the negative electrode composite was changed. The solid electrolyte in Comparative Examples 4 and 5 was Li ７－ｘ P.S. ６－ｘ Cl ｘThe sulfide-based solid electrolyte represented by (x = 1) was used. Other conditions in Comparative Examples 4 and 5 were the same as in Example 1. The D / G ratios of the carbon materials used as the conductive additives in Comparative Examples 2 to 4 and the half-widths of the diffraction peaks attributable to the (002) plane in the XRD patterns are shown below. Comparative Example 4: D / G ratio 0.3, (002) peak half-width 1.1° Comparative Example 5: D / G ratio 1.2, (002) peak half-width 4.7°

[0085] The half-cell conditions and charge / discharge efficiencies of Examples 1 to 6 and Comparative Examples 1 to 4 are summarized in the table below. In Table 1, LTO is Li ４ Ti ５ O １２ LZSOC is an abbreviation for Li ２ Zr(SO ４ ) Cl ４ LPSC is an abbreviation for Li ７－ｘ P.S. ６－ｘ Cl ｘ The D / G ratio represents the D / G ratio of the carbon material, and the (002) FWHM represents the half-width of the diffraction peak attributable to the (002) plane in the X-ray diffraction spectrum of the carbon material.

[0086]

[0087] Examples 1 to 7, in which the D / G ratio was 1.1 or less, had higher charge / discharge efficiency than Comparative Examples 1 to 3, in which the D / G ratio was greater than 1.1. This is thought to be due to the high crystallinity of the carbon material constituting the conductive additive. A highly crystalline conductive additive has fewer functional groups attached to its surface and is less likely to cause reductive decomposition of the solid electrolyte. Reductive decomposition of the solid electrolyte reduces the charge / discharge efficiency of an all-solid-state battery; if reductive decomposition of the solid electrolyte does not progress, the charge / discharge efficiency of the all-solid-state battery will be higher.

[0088] Furthermore, Examples 1 to 3 and 7, in which the D / G ratio was 0.05 or more and 1.0 or less and the half-width of the diffraction peak belonging to the (002) plane in the XRD pattern was 1.9° or less, had higher charge / discharge efficiency than Examples 4 to 6. This is thought to be because the carbon material constituting the conductive additive of Examples 1 to 3 and 7, which satisfied the above conditions, was particularly highly crystalline.

[0089] Furthermore, in Comparative Examples 4 and 5, in which the solid electrolyte was not a halide-based solid electrolyte, varying the D / G ratio of the carbon material did not result in a significant difference in the charge / discharge efficiency of the all-solid-state battery. Because halide-based solid electrolytes are prone to reductive decomposition, it is necessary to control the D / G ratio of the carbon material. In contrast, solid electrolytes other than halide-based solid electrolytes are less prone to reductive decomposition than halide-based solid electrolytes, and it is thought that control of the D / G ratio of the carbon material is not necessary. In other words, controlling the D / G ratio of the carbon material in a system containing a halide-based solid electrolyte increases the charge / discharge efficiency of the all-solid-state battery, which is an advantageous effect that cannot be found by changing the D / G ratio of the carbon material in a system containing a solid electrolyte other than a halide-based solid electrolyte.

[0090] The negative electrode for an all-solid-state battery of this embodiment is suitably applied to an all-solid-state battery containing a halide-based solid electrolyte.

[0091] REFERENCE SIGNS LIST 10 solid electrolyte layer 20 positive electrode 22 positive electrode current collector 24 positive electrode active material layer 30 negative electrode 32 negative electrode current collector 34 negative electrode active material layer 40 power generating element 50 exterior body 52 metal foil 54 resin layer 60, 62 terminals.

Claims

1. It contains a living substance, a carbon material, and a solid electrolyte, and the solid electrolyte is Li ａ E ｂ G ｃ X ｄ ... represented by (1). In formula (1), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanoids, and G is OH, BO ２ , BO ３ , BO ４ , B ３ O ６ , B ４ O ７ , CO ３ , NO ３ , AlO ２ , SiO ３ , SiO ４ , Si ２ O ７ , Si ３ O ９ , Si ４ O １１ , Si ６ O １８ , PO ３ , PO ４ , P ２ O ７ , P ３ O １０ , SO ３ , SO ４ , SO ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , BF ４ , PF ６ , BOB, (COO) ２ , N, AlCl ４ , CF ３ SO ３ , CH ３ COO, CF ３ COO, OOC-(CH ２ ) ２ , OOC-CH ２ -COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH(OH)-CH ２ -COO, C ６ H ５ SO ３ 、OOC-CH=CH-COO, C(OH)(CH ２ COOH) ２ COO, AsO ４ 、BiO ４ 、CrO ４ 、MnO ４ 、PtF ６ 、PtCl ６ 、PtBr ６ 、PtI ６ 、SbO ４ 、SeO ４ 、TeO ４ 、At least one group selected from the group consisting of -HCOO, O, X is Cl or at least one element selected from the group consisting of Cl, F, Br, and I, a satisfies 0.5 ≤ a < 6, b satisfies 0 < b < 2, c satisfies 0 ≤ c ≤ 6, d satisfies 0 < d ≤ 6.1, the D / G ratio of the carbon material satisfies 0 or more and 1.10 or less, and the D / G ratio is the intensity ratio obtained by dividing the peak intensity of the D band peak occurring near 1360 cm －１ by the peak intensity of the G band peak occurring near 1600 cm －１ in the Raman spectrum measured by Raman spectroscopy. Anode for all-solid-state battery.

2. The half-value width of the diffraction peak attributed to the (002) plane of the diffraction spectrum obtained by measuring the carbon material by X-ray diffraction method is 0.1° or more and 2.0° or less. The negative electrode for all-solid-state battery according to claim 1.

3. In the formula (1), E is Al or Zr, and G is PO ３ , PO ４ , P ２ O ７ , P ３ O １０ , SO ３ , SO ４ , SO ５ , S ２ O ３ , S ２ O ４ , S ２ O ５ , S ２ O ６ , S ２ O ７ , S ２ O ８ , at least one group selected from the group consisting of O, and X is Cl. The negative electrode for an all-solid-state battery according to claim 1.

4. The active material includes a carbon material selected from the group consisting of natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fiber (MCF), cokes, glassy carbon, and fired organic compounds, a metal, alloy, or composite material capable of reacting with lithium, an oxide, or metallic lithium. The negative electrode for all-solid-state battery according to claim 1.

5. An all-solid-state battery comprising the negative electrode for all-solid-state battery according to any one of claims 1 to 4.

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