JP2023117209A - Negative electrode for solid electrolyte battery and solid electrolyte battery - Google Patents

Abstract

To provide a negative electrode for a solid electrolyte battery and a solid electrolyte battery that have excellent initial charge/discharge efficiency.SOLUTION: The negative electrode for a solid electrolyte battery includes a negative electrode active material, a first compound, and an organic material that is supported by the negative electrode active material and forms an SEI film on an interface with the negative electrode active material to protect the negative electrode active material during an initial charging process. The first compound is AaEbGcXd...(1). In formula (1), A is Li, or at least one of Na and Ca and Li, E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanides, G is a predetermined group, X is at least one element selected from the group consisting of F, Cl, Br, and I, and 0.5≤a<6, 0<b<2, and 0.1<c≤6, 0<d≤6.1 are satisfied.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a negative electrode for a solid electrolyte battery and a solid electrolyte battery.

2. Description of the Related Art In recent years, the development of electronics technology has been remarkable, and efforts have been made to reduce the size, weight, thickness, and functions of portable electronic devices. Along with this, there is a strong demand for batteries that serve as power sources for electronic devices to be smaller, lighter, thinner, and more reliable. As solid electrolytes, oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, and the like are known.

For example, Patent Literature 1 describes a solid electrolyte battery using an oxide-based solid electrolyte. Further, Patent Document 2 describes an all-solid battery using a complex hydride solid electrolyte containing an alkali metal compound. Further, Patent Document 3 describes an all-solid lithium battery using a sulfide-based solid electrolyte containing lithium halide. Patent Documents 1 to 3 describe that the addition of lithium halide to an electrode may improve various properties.

JP 2019-91583 A JP 2016-18679 A JP 2017-79126 A

Oxide-based solid electrolytes, sulfide-based solid electrolytes, and complex hydride-based solid electrolytes have different properties because of their different constituent materials. In recent years, halide-based solid electrolytes have been investigated as solid electrolytes that may have higher ionic conductivity than these solid electrolytes.

A solid electrolyte battery using a halide-based solid electrolyte has a large irreversible capacity during the initial charge/discharge, and the initial charge/discharge efficiency may not be sufficient.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a negative electrode for a solid electrolyte battery and a solid electrolyte battery that are excellent in initial charge/discharge efficiency.

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

(1) A negative electrode for a solid electrolyte battery according to the first aspect includes a negative electrode active material, a first compound, and a negative electrode active material supported on the negative electrode active material, and the negative electrode active material is supported at the interface with the negative electrode active material during an initial charging process. and organics that form a protective SEI coating. _The first compound _{is AaEbGcXd (} 1) _. In formula (1), A is Li, or at least one of Na and Ca and Li, and E is Al, Sc, Y, Zr, Hf, at least one selected from the group consisting of lanthanoids is _an element and G is OH, _{BO2 , BO3} , BO4, _B3O6 , _B4O7 , _CO3 , _NO3 , _AlO2 , _{SiO3 , SiO4} , _{Si2O7 , Si3O 9} , _{Si4O11 , Si6O18 , PO3, PO4, P2O7 , P3O10 , SO3 , SO4 , SO5 , S2O3 , S2O4 , S2O 5} , _S2O6 , _{S2O7 , S2O8} , _BF4 , _PF6 , BOB, ( _COO ) _{2 ,} N, _AlCl4 , _{CF3SO3 , CH3COO} , _CF3COO , 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, _OOC -CH=CH-COO, C(OH)( _CH2COOH ) _2COO , AsO4, _BiO4 , _CrO4 , _MnO4 , _PtF6 , _PtCl6 , PtBr6, _{PtI6 ,} At least one group selected from the group consisting of SbO ₄ , SeO ₄ , TeO ₄ , HCOO and O; X is at least one element selected from the group consisting of F, Cl, Br and I; Further, 0.5≦a<6, 0<b<2, 0≦c≦6, and 0<d≦6.1 are satisfied.

(2) The solid electrolyte battery negative electrode according to the above aspect may further include a second compound. The second compound is Li _a E _b X _d (2) unlike the first compound. In formula (2), E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanides, and X is selected from the group consisting of F, Cl, Br, and I. It is at least one element and satisfies 0.5≦a<6, 0<b<2, and 0<d≦6.1.

(3) In the solid electrolyte battery negative electrode according to the above aspect, the organic substance is ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propanesultone, divinyl adipate, vinyl acetate, ethylene sulfide, chloroethylene carbonate, catechol carbonate, methanesulfone. Any selected from the group consisting of propynyl acid, lithium bis[1,2-oxalato(2)-O,O']borate, and lithium difluoromono[1,2-dioxalato(2)-O,O']borate , or a polymer thereof.

(4) The negative electrode for a solid electrolyte battery according to the above aspect may further contain a lithium salt having a molecular weight smaller than that of the first compound.

(5) In the negative electrode for a solid electrolyte battery according to the aspect described above, the organic matter may be solid at room temperature.

(6) The negative electrode for a solid electrolyte battery according to the above aspect may further include the SEI coating that coats the negative electrode active material. The SEI coating includes an organic SEI coating formed on the interface between the organic substance and the negative electrode active material, and an inorganic SEI coating formed between the first compound and the negative electrode active material.

(7) A solid electrolyte battery according to a second aspect includes a solid electrolyte battery negative electrode according to the above aspect, a positive electrode, and a solid electrolyte layer containing a solid electrolyte between the solid electrolyte battery negative electrode and the positive electrode. , provided.

(8) In the solid electrolyte battery according to the above aspect, the solid electrolyte may be the same as the first compound.

The negative electrode for a solid electrolyte battery and the solid electrolyte battery according to the above aspect are excellent in initial charge/discharge efficiency.

It is a cross-sectional schematic diagram of the solid electrolyte battery concerning this embodiment. 1 is a schematic diagram of a negative electrode mixture according to an embodiment; FIG. FIG. 2 is a schematic diagram of a characterizing portion of the negative electrode mixture according to the present embodiment; FIG. 2 is an image diagram of an organic substance supported on a negative electrode active material when the negative electrode active material is graphite in the negative electrode mixture according to the present embodiment. FIG. 3 is an image diagram of the vicinity of the negative electrode active material after initial charging and discharging. It is a schematic diagram of a characterizing portion of a negative electrode mixture according to a modification of the present embodiment.

Hereinafter, this embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, there are cases where characteristic portions are enlarged for convenience in order to make it easier to understand the features of the present invention, and the dimensional ratios of each component may differ from the actual ones. be. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be implemented with appropriate modifications without changing the gist of the invention.

[Solid electrolyte battery]
FIG. 1 is a schematic cross-sectional view of a solid electrolyte battery 100 according to this embodiment. A solid electrolyte battery 100 shown in FIG. 1 includes a power generation element 40 and an exterior body 50 . The exterior body 50 covers the periphery of the power generation element 40 . The power generation element 40 is connected to the outside by a pair of connected terminals 60 and 62 . In FIG. 1, a laminated battery is shown, but a wound battery may also be used. The solid electrolyte battery 100 is used, for example, as a laminate battery, a prismatic battery, a cylindrical battery, a coin battery, a button battery, and the like.

<Power generation element>
The power generation 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 transferring ions between the positive electrode 20 and the negative electrode 30 via the solid electrolyte layer 10 and transferring electrons via an external circuit.

"Solid electrolyte layer"
Solid electrolyte layer 10 is sandwiched between positive electrode 20 and negative electrode 30 . The solid electrolyte layer 10 includes a solid electrolyte capable of moving ions by an externally applied voltage. For example, solid electrolytes conduct lithium ions and impede the movement of electrons.

The solid electrolyte contains lithium, for example. The solid electrolyte may be, for example, an oxide-based material, a sulfide-based material, or a halide-based material.

The solid electrolyte is _, for example, a _halide - _based solid electrolyte represented by _AaEbGcXd (1). The solid electrolyte may be in the state of powder (particles), or may be in the state of a sintered body obtained by sintering powder. Solid electrolytes are produced by compressing and molding powder, by molding a mixture of powder and binder, by applying paint containing powder, binder and solvent, and then heating to remove the solvent. A formed coating film may be used.

A is Li, or at least one of Na and Ca and Li. When A contains Na or Ca, the ratio of Li to Na or Ca is preferably 1.00:0.03 to 1.00:0.20 in terms of molar ratio (Li:Na or Ca), It is more preferably 1.00:0.04 to 1.00:0.10. Within this range, the potential window on the reduction side of the solid electrolyte layer 10 is widened.

a satisfies 0.5≦a<6, preferably 2.0≦a≦4.0, more preferably 2.5≦a≦3.5. When E is Zr or Hf, a is preferably 1.0≤a≤3.0, more preferably 1.5≤a≤2.5. In the compound represented by the formula (1), when a is 0.5≦a<6, the content of Li contained in the compound becomes appropriate, and the ion conductivity of the solid electrolyte layer 10 increases.

E is an essential component, Al, Sc, Y, Zr, Hf, lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu ) is at least one element selected from the group consisting of E preferably contains Al, Sc, Y, Zr, Hf and La, more preferably Zr and Y. E improves the ionic conductivity of the solid electrolyte layer 10 . b is 0<b<2. Since the effect of including E can be obtained more effectively, b preferably satisfies 0.6≦b. E is an element that forms the skeleton of the solid electrolyte layer 10 . More preferably, b satisfies b≦1.

G is, _for example, OH _{, BO2 , BO3} , BO4, _B3O6 , _B4O7 , CO3, _NO3 , _AlO2 , _{SiO3 , SiO4 , Si2O7 , Si3O9} , _{Si4O11 , Si6O18 , PO3 , PO4} , _P2O7 , _{P3O10 , SO3} , _SO4 , _{SO5 , S2O3 , S2O4 , S2O5} , 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-( _CH2 ) ₂ -COO, OOC-CH2 _- COO, OOC- _CH (OH ₎ -CH(OH)-COO, OOC-CH(OH)-CH2 _- COO, _C6H5SO3 , OOC-CH =CH-COO, _OOC -CH=CH-COO, C(OH)( _CH2COOH ) _2COO , AsO4, _BiO4 , _CrO4 , _{MnO4 , PtF6} , PtCl6, _PtBr6 , _PtI6 , SbO ₄ , SeO ₄ , TeO ₄ and HCOO. G is preferably at least one group selected from the group consisting of OH, SO ₄ , CH ₃ COO, CF ₃ COO, HCOO and O, particularly preferably SO ₄ . When G is included, the potential window on the reduction side of the solid electrolyte layer 10 is widened, making reduction difficult.

c satisfies 0≦c≦6. c is preferably 0.5≦c, since the effect of widening the potential window on the reduction side due to the inclusion of G becomes more pronounced. c is preferably c≦3 so that the ionic conductivity of the solid electrolyte does not decrease due to excessive G content.

X is at least one selected from the group consisting of F, Cl, Br and I; X is preferably at least one selected from the group consisting of Cl, Br, and I, and preferably contains Br and/or I, particularly I, in order to increase the ionic conductivity of the solid electrolyte. preferably included. When X contains F, it preferably contains F and two or more selected from the group consisting of Cl, Br, and I because X forms a solid electrolyte with high ionic conductivity.

When X is F, the solid electrolyte has sufficiently high ionic conductivity and excellent oxidation resistance. When X is Cl, the solid electrolyte has high ionic conductivity and well-balanced oxidation resistance and reduction resistance. When X is Br, the solid electrolyte has sufficiently high ionic conductivity and a good balance between oxidation resistance and reduction resistance. When X is I, the solid electrolyte has high ionic conductivity.

d satisfies 0<d≦6.1. d is preferably 1≤d. When d is 1≦d, the strength of the pellet increases when the solid electrolyte is press-molded into a pellet. Further, when d is 1≦d, the ionic conductivity of the solid electrolyte increases. Further, d is preferably d≦5 so that the potential window of the solid electrolyte is not narrowed due to insufficient G due to excessive X content.

_The solid electrolyte _is , for _example , _Li2ZrSO4Cl4 , _Li2ZrCO3Cl4 , _{Li2Zr (} (COO) _{2 ) 0.5Cl5 , Li2Zr} ( _CH3COO ) _{0.2Cl5.8 , Li2Zr ( CF3COO ) 0.2Cl5.8 , Li2Zr} (HCOO _{) 0.4Cl5.6 , Li2ZrBO2Cl5} , _{Li2ZrBF4Cl5 , Li3YSO4Cl 4 , Li3YCO3Cl4 , Li3YBO2Cl5 , Li3YBF4Cl5 . _ _}

"positive electrode"
As shown in FIG. 1 , the positive electrode 20 has a plate-like (foil-like) positive electrode current collector 22 and a positive electrode mixture layer 24 . The positive electrode mixture layer 24 is in contact with at least one surface of the positive electrode current collector 22 .

(Positive electrode current collector)
The positive electrode current collector 22 may be made of an electronically conductive material that resists oxidation during charging and does not easily corrode. The positive electrode current collector 22 is, for example, a metal such as aluminum, stainless steel, nickel, or titanium, a conductive resin, or the like. The positive electrode current collector 22 may be in the form of powder, foil, punched, or expanded.

(Positive electrode mixture layer)
The positive electrode mixture layer 24 contains a positive electrode active material and, if necessary, a solid electrolyte, a binder and a conductive aid.

(Positive electrode active material)
The positive electrode active material is not particularly limited as long as it is capable of reversibly occluding/releasing, inserting/deintercalating lithium ions (intercalation/deintercalation), and is used in known solid electrolyte batteries. can be used. Examples of positive electrode active materials include lithium-containing metal oxides and lithium-containing metal phosphates.

Lithium- _containing metal oxides _{include ,} for example, lithium cobaltate ( _LiCoO2 ), lithium nickelate ( _LiNiO2 ), _lithium manganese spinel ( _LiMn2O4 ), and general formula: _{LiNixCoyMnzO2} (x+y+z = 1), lithium vanadium compounds ( _LiVOPO4 , _Li3V2 ( _PO4 ) ₃ ), _olivine -type _LiMPO4 (wherein M is selected from Co, Ni, Mn, Fe, at least one of which is shown), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), and the like.

Moreover, the positive electrode active material may not contain lithium. Such positive electrode active materials include lithium-free metal oxides ( _MnO2 , _{V2O5 ,} etc.), lithium-free metal sulfides ( _MoS2, etc.), lithium-free fluorides ( _FeF3 , VF3 _, etc.). ) and the like. When using a positive electrode active material that does not contain lithium, the negative electrode is previously doped with lithium ions, or a negative electrode containing lithium ions is used.

(binder)
The binder binds the positive electrode active material, the solid electrolyte, and the conductive aid to each other in the positive electrode mixture layer 24 and firmly bonds the positive electrode mixture layer 24 and the positive electrode current collector 22 together. The positive electrode mixture layer 24 preferably contains a binder. The binder preferably has oxidation resistance and good adhesion.

Binders used in the positive electrode mixture layer 24 include polyvinylidene fluoride (PVDF) or its copolymer, polytetrafluoroethylene (PTFE), polyamide (PA), polyimide (PI), polyamideimide (PAI), polybenzimidazole ( PBI), polyethersulfone (PES), polyacrylic acid (PA) and its copolymer, metal ion cross-linked polyacrylic acid (PA) and its copolymer, maleic anhydride-grafted polypropylene (PP) , maleic anhydride-grafted polyethylene (PE), or mixtures thereof. Among these, it is particularly preferable to use PVDF as the binder.

The content of the solid electrolyte in the positive electrode mixture layer 24 is not particularly limited, but is preferably 1% by mass to 50% by mass based on the total mass of the positive electrode active material, the solid electrolyte, the conductive aid, and the binder. Preferably, it is 5% by mass to 30% by mass.

The content of the binder in the positive electrode mixture layer 24 is not particularly limited, but is preferably 1% by mass to 15% by mass based on the total mass of the positive electrode active material, the solid electrolyte, the conductive aid and the binder. , 3% by mass to 5% by mass. If the amount of binder is too small, there is a tendency that the positive electrode 20 with sufficient adhesive strength cannot be formed. Conversely, if the amount of binder is too large, it tends to be difficult to obtain a sufficient volume or mass energy density because general binders are electrochemically inactive and do not contribute to discharge capacity.

(Conductivity aid)
The conductive aid improves the electron conductivity of the positive electrode mixture layer 24 . A well-known thing can be used for a conductive support agent. Examples of conductive aids 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. be. The conductive aid may be in the form of powder or fiber.

The content of the conductive aid in the positive electrode mixture layer 24 is not particularly limited. When adding a conductive aid, the mass ratio of the conductive aid is usually 0.5% by mass to 20% by mass based on the total mass of the positive electrode active material, the solid electrolyte, the conductive aid, and the binder. It is preferably 1% by mass to 5% by mass.

"negative electrode"
As shown in FIG. 1 , the negative electrode 30 has a negative electrode current collector 32 and a negative electrode mixture layer 34 . The negative electrode mixture layer 34 is in contact with the negative electrode current collector 32 .

(Negative electrode current collector)
The negative electrode current collector 32 may have electronic conductivity. The negative electrode current collector 32 is, 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 powder, foil, punched, or expanded form.

(Negative electrode mixture layer)
The negative electrode mixture layer 34 includes a negative electrode active material 34A, a first compound 34B, and an organic substance 34C. FIG. 2 is an enlarged schematic diagram of a characterizing portion of the negative electrode mixture layer 34 . The negative electrode mixture layer 34 may contain a binder and a conductive aid 34D. A known material can be used for the binder and the conductive aid 34D. The conductive aid 34D is, for example, carbon black. FIG. 3 is an enlarged schematic view of the vicinity of one negative electrode active material 34A of the negative electrode mixture layer 34. As shown in FIG.

The negative electrode active material 34A is not particularly limited as long as it can reversibly absorb and desorb lithium ions and insert and desorb lithium ions. A negative electrode active material used in known solid electrolyte batteries can be used for the negative electrode active material 34A.

The negative electrode active material 34A includes, for example, carbon materials such as natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fibers (MCF), cokes, vitreous carbon, and baked organic compounds, Si, SiO _x , Sn, and aluminum. metals that can be combined with lithium, alloys thereof, composite materials of these metals and carbon materials, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), oxides such as SnO ₂ , metallic lithium, and the like. The negative electrode active material 34A is preferably natural graphite.

_The first compound 34B is _{AaEbGcXd (} 1) _. The first compound 34B is the same material as the halide-based solid electrolyte described above. The first compound 34B and the solid electrolyte used for the solid electrolyte layer 10 may be different or the same.

The organic matter 34C is carried on the negative electrode active material 34A. FIG. 4 is an image diagram of an organic substance 34C supported on the negative electrode active material when the negative electrode active material 34A is graphite. The organic substance 34C is, for example, scattered and carried at a plurality of locations of the negative electrode active material 34A. FIG. 4 shows the state in the vicinity of the negative electrode active material 34A before the initial charging and discharging are repeated.

The organic substance 34C is an organic substance that forms an SEI film that protects the negative electrode active material 34A at the interface with the negative electrode active material 34A during the initial charging process. The SEI (Solid electrolyte interphase) film is a layer formed on the surface of the negative electrode active material of the battery during charging and discharging processes. Lithium ions can pass through the SEI coating, while large molecular weight molecules that migrate with the lithium ions cannot pass through the SEI coating. Therefore, the formation of the SEI coating protects the negative electrode active material from side reactions. The SEI coating is a protective layer that protects the negative electrode active material.

A part of the organic substance 34C is decomposed during the initial charge/discharge process to form an SEI coating. A part of the organic matter 34C remains in the negative electrode mixture layer 34 unreacted. An example of the initial charge-discharge process is, in half-cell measurement of the negative electrode, after charging to 5 mV (vs. Li/Li ⁺ ) at a current of 0.01 C, 3.0 V (vs. Li/Li ⁺ ) at a current of 0.01 C. This is the process of discharging up to In other words, the organic matter 34C is charged to 5 mV (vs. Li/Li ⁺ ) at a current of 0.01 C and then discharged to 3.0 V (vs. Li/Li ⁺ ) at a current of 0.01 C. is an organic substance that decomposes and forms an SEI film.

Organic substance 34C specifically includes ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylene carbonate (VC), propane sultone, divinyl adipate, vinyl acetate, ethylene sulfide, chloroethylene carbonate, catechol carbonate, methanesulfone. The group consisting of propynyl acid, lithium bis[1,2-oxalato(2)-O,O']borate (LiBOB), lithium difluoromono[1,2-dioxalato(2)-O,O']borate (LiDFOB) or a polymer thereof.

Organic matter 34C is preferably solid at room temperature. Room temperature is, for example, 25°C. Ethylene carbonate, propane sultone, and divinyl adipate are solids at room temperature.

FIG. 5 is an image diagram of the state in the vicinity of the negative electrode active material 34A after the initial charging and discharging. An SEI coating 35 is formed around the negative electrode active material 34A. Lithium ions can pass through the SEI coating 35 . A mixed salt 37 of the organic substance 34C and the first compound 34B may also be present around the SEI coating 35 . Although not shown, the unreacted organic matter 34C may remain supported on the negative electrode active material 34A.

The SEI coating 35 has an organic SEI coating and an inorganic SEI coating. The SEI coating 35 has, for example, a portion dominated by an organic SEI coating and a portion dominated by an inorganic SEI coating. A predominant portion means that 50% or more in a specific region is dominated by a specific structure.

The organic SEI coating is formed by decomposition of the organic matter 34C. At the interface between the first compound 34B and the organic substance 34C contained in the negative electrode mixture layer 34, lithium ions are coordinated with the organic substance to form a coordination structure. At the interface between the portion where this coordination structure is formed and the negative electrode active material 34A, an SEI film that is stable at room temperature is formed during the initial charge. This reaction is presumed to occur due to the property of the first compound 34A to easily liberate lithium ions. An organic SEI coating is formed on the interface between the organic substance 34C and the negative electrode active material 34A. As shown in FIG. 4, the organic substance 34C is scattered and carried at a plurality of locations of the negative electrode active material 34A, so that the SEI coating 35 has a portion dominated by the organic SEI coating.

The inorganic SEI coating is formed by decomposition of the first compound 34B. An inorganic SEI coating is formed between the first compound 34B and the negative electrode active material 34A.

Organic SEI coatings are thinner than inorganic SEI coatings. For example, the organic SEI coating has a thickness of several nm to several tens of nm, and the inorganic SEI coating has a thickness of several tens of nm to several hundreds of nm.

The mixed salt 37 of the organic substance 34C and the first compound 34B is formed by liberating the lithium ions of the first compound 34B and coordinating with the organic substance.

Moreover, the negative electrode mixture layer 34 may further include a second compound 34E. FIG. 6 is an enlarged view of a characterizing portion of the negative electrode mixture layer according to the modification. The second compound 34E is different from the first compound 34B. _The second compound 34E _is represented by _LiaEbXd (2). In formula (2), the definitions of X, E, a, b, and d are the same as in formula (1) above.

In the compound represented by formula (2), for example, E is at least one element selected from the group consisting of Al, Zr, and Hf, and 0.5≦a<3, 0<b<0.05 , 0<d≦3. The compound represented by the formula (2) preferably contains at least one of Zr as E, Cl, and I as X.

The second compound 34E is, for example, between the negative electrode active material 34A and the first compound 34B. The second compound 34E prevents the reaction between the negative electrode active material 34A and the first compound 34B and suppresses decomposition of the first compound 34B.

The second compound 34E, for example, covers at least part of the circumference of the negative electrode active material 34A. The second compound 34E preferably covers 30% or more of the peripheral length of the negative electrode active material 34A in a cross section of the negative electrode mixture layer 34 cut along the stacking direction. A cross-sectional image can be confirmed with, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The compound represented by formula (2) is easily deformed by physical force and is chemically compatible. Therefore, the second compound 34E receives a physical force and coats the surface of the negative electrode active material 34A. Further, the second compound 34E has high compatibility with the first compound 34B, so that it bonds between the negative electrode active material 34A and the first compound 34B at the molecular level.

The mass % of the first compound 34B contained in the negative electrode mixture layer 34 is, for example, greater than the mass % of the organic matter 34C. Also, the mass % of the first compound 34B contained in the negative electrode mixture layer 34 is, for example, greater than the mass % of the second compound 34E. The mass % of the organic matter 34C contained in the negative electrode mixture layer 34 is, for example, greater than the mass % of the second compound 34E.

The mass % of the negative electrode active material 34A contained in the negative electrode mixture layer 34 is, for example, 50 mass % or more, preferably 60 mass % or more. The mass % of the first compound 34B contained in the negative electrode mixture layer 34 is, for example, 20 mass % or more and 30 mass % or less. The mass % of the organic substance 34C contained in the negative electrode mixture layer 34 is, for example, 10 mass % or less. The mass % of the second compound 34E is, for example, 10 mass % or less.

The average particle size of the negative electrode active material 34A is larger than, for example, the average particle size of the organic substance 34C or the second compound 34E. When the conditions are satisfied, the organic substance 34C and the second compound 34E are easily formed between the negative electrode active material 34A and the first compound 34B.

The average particle size is obtained from a cross-sectional image of the negative electrode mixture layer 34 cut along the stacking direction. A cross-sectional image can be confirmed with, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM). 10 negative electrode active materials 34A, 10 first compounds 34B, 10 organic substances 34C, and 10 second compounds 34E, which can be confirmed in cross-sectional images, are extracted, and their average is determined to obtain the average particle diameter. Each substance can be cut out from the contrast of the image and extracted respectively. When the negative electrode active material 34A, the first compound 34B, the organic substance 34C, and the second compound 34E are amorphous, the diameter in the major axis direction is taken as the particle size.

Moreover, the negative electrode mixture layer 34 may further contain a lithium salt having a molecular weight smaller than that of the first compound 34B. By mixing lithium salts with different molecular weights, formation of a lithium ion coordination structure at the interface between the first compound 34B and the organic substance 34C is promoted, and the irreversible capacity of the solid electrolyte battery 100 is reduced. Lithium _salts include, for example, LiF, LiCl, LiBr, LiI, _LiPF6 , _lithium borofluoride ( _LiBF4 ), _LiClO4 , _{LiCF3SO3 , LiCF3CF2SO3 ,} LiC( _CF3SO2 ) ₃ , LiN ( _SO2F ) ₂ , LiN( _{CF3SO2 ) 2} , _LiN ( _{CF3CF2SO2 ) 2 ,} LiN( _{CF3SO2 )} ( _{C4F9SO2 )} , _LiN ( _CF3CF2CO ) ₂ , LiBOB, LiN(FSO ₂ ) ₂ and the like.

<Exterior body>
The exterior body 50 accommodates the power generating element 40 therein. The exterior body 50 prevents intrusion of water or the like from the outside to the inside. The exterior body 50 has a metal foil 52 and a resin layer 54 laminated on each surface of the metal foil 52, as shown in FIG. 1, for example. The exterior body 50 is a metal laminate film in which a metal foil 52 is coated with a resin layer 54 from both sides.

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

<Terminal>
Terminals 60 and 62 are connected to positive electrode 20 and negative electrode 30, respectively. A terminal 60 connected to the positive electrode 20 is a positive terminal, and a terminal 62 connected to the negative electrode 30 is a negative terminal. Terminals 60 and 62 are responsible for electrical connection with the outside. Terminals 60, 62 are made of a conductive material such as aluminum, nickel, or copper. The connection method may be welding or screwing. Terminals 60, 62 are preferably protected with insulating tape to prevent short circuits.

[Method for producing solid electrolyte battery]
Next, a method for manufacturing the solid electrolyte battery according to this embodiment will be described. First, a solid electrolyte is prepared. A solid electrolyte can be produced, for example, by mixing raw material powders containing predetermined elements in a predetermined molar ratio and causing a mechanochemical reaction. Alternatively, a solid electrolyte of a sintered body may be formed by mixing raw material powders containing a predetermined element in a predetermined molar ratio, molding, and sintering in a vacuum or in an inert gas atmosphere.

When the raw material powder contains a halide raw material, the halide raw material tends to evaporate when the temperature is raised. Therefore, a halogen gas may coexist in the atmosphere during sintering to compensate for the halogen. Moreover, when the raw material powder contains a halide raw material, it may be sintered by a hot press method using a highly airtight mold. In this case, since the mold is highly sealed, evaporation of the halide raw material due to sintering can be suppressed. By sintering in this manner, a solid electrolyte in the form of a sintered body made of a compound having a predetermined composition is obtained.

Moreover, when manufacturing a solid electrolyte, you may heat-process as needed. By performing heat treatment, the crystallite size of the solid electrolyte can be adjusted. The heat treatment is preferably carried out at 130° C. to 650° C. for 0.5 to 60 hours, more preferably at 140° C. to 600° C. for 1 to 30 hours, in an argon gas atmosphere. A solid electrolyte having a crystallite size of 5 nm to 500 nm can be obtained by carrying out in an argon gas atmosphere at 150 to 550° C. for 5 to 24 hours.

Next, the positive electrode 20 is prepared. The positive electrode is manufactured by applying a paste containing a positive electrode active material on the positive electrode current collector 22 and drying it to form the positive electrode mixture layer 24 .

Next, the negative electrode 30 is prepared. First, the negative electrode active material 34A is made to support the organic matter 34C. The organic substance 34C is supported on the surface of the negative electrode active material 34A by, for example, dry-mixing the negative electrode active material 34A and the organic substance 34C. Alternatively, the organic substance 34C may be supported on the surface of the negative electrode active material 34A by a wet mixing method in which the organic substance 34C is added to a solvent and then mixed with the negative electrode active material 34A. Lithium salts may also be added during dry mixing or wet mixing. Next, a paste obtained by mixing the negative electrode active material 34 supported by the organic substance 34C and the first compound 34B is applied to the negative electrode current collector 32 . Then, the coating film is dried to form the negative electrode mixture layer 34 . A second compound 34E may be added to the paste if necessary.

The power generation element 40 can be produced using, for example, a powder molding method. A guide having a hole is placed on the positive electrode 20, and the guide is filled with a solid electrolyte. After that, the surface of the solid electrolyte is smoothed, and the negative electrode 30 is placed on top of the solid electrolyte. Thereby, the solid electrolyte is sandwiched between the positive electrode 20 and the negative electrode 30 . After that, pressure is applied to the positive electrode 20 and the negative electrode 30 to pressure-mold the solid electrolyte. A laminated body in which the positive electrode 20, the solid electrolyte layer 10, and the negative electrode 30 are laminated in this order is obtained by pressure molding.

Next, external terminals are welded by a known method to the positive electrode current collector 22 of the positive electrode 20 and the negative electrode current collector 32 of the negative electrode 30 forming the laminate, respectively, and the positive electrode current collector 22 or the negative electrode current collector is 32 and an external terminal are electrically connected. After that, the laminate connected to the external terminals is housed in the exterior body 50, and the opening of the exterior body 50 is heat-sealed to seal. Solid electrolyte battery 100 of the present embodiment is obtained through the above steps.

In the solid electrolyte battery 100 according to the present embodiment, the negative electrode mixture layer 34 includes the organic substance 34C, so that a stable SEI coating can be formed on the surface of the negative electrode active material 34A. The SEI coating resulting from decomposition of the organic substance 34C is formed thinner than the SEI coating resulting from decomposition of the first compound 34B. That is, the SEI coating accompanying decomposition of the organic matter 34C consumes less chemical capacity than the SEI coating accompanying decomposition of the first compound 34B. By decomposing the organic matter 34C instead of the first compound 34B and suppressing the decomposition of the first compound 34B, the irreversible capacity of the solid electrolyte battery 100 is reduced and the initial charge/discharge efficiency is improved.

As described above, the embodiments of the present invention have been described in detail with reference to the drawings. , substitutions, and other modifications are possible.

"Example 1"
(Preparation of solid electrolyte)
In a glove box with a dew point of about −70° C., raw material powders of zirconium chloride (ZrCl ₄ ) and lithium sulfate (Li ₂ SO ₄ ) were weighed out in a molar ratio of 1:1. The raw material powder was charged into a zirconia airtight container for a planetary ball mill containing zirconia balls in advance. Next, the sealed container was covered with a lid, the lid was screwed to the container body, and the gap between the lid and the container was sealed with polyimide tape. Polyimide tape has the effect of blocking moisture. Next, the zirconia airtight container was set in a planetary ball mill. A rotation speed of 500 rpm and a rotation speed of 500 rpm were set, and the rotation direction of rotation and the rotation direction of revolution were reversed, and mechanochemical reaction was carried out for 24 hours to generate a solid electrolyte (Li ₂ ZrSO ₄ Cl ₄ ).

The obtained solid electrolyte had an average primary particle size of 0.1 μm. The planetary ball mill is usually installed in the atmosphere (atmosphere). The sealed zirconia container for the planetary ball mill is screwed and sealed with polyimide tape. Even so, it is considered that the zirconia sealed container hardly contains moisture from the atmosphere.

(Preparation of negative electrode mixture)
A negative electrode mixture was also prepared in a glove box with a dew point of about -70°C. Graphite (Gr) having an average particle size of 11.0 μm was used as the negative electrode active material 34A. The nominal capacity of this graphite is 342 mAhg ⁻¹ . Also, the same solid electrolyte as described above was used as the first compound 34B. Ethylene carbonate (EC) was used as the organic substance 34C. The negative electrode active material 34A, the first compound 34B, and the insulator 34C were weighed so that the mass ratio was 70: _29.25 : _0.75 (=Gr: _Li2ZrSO4Cl4 :EC), A negative electrode mixture was obtained by mixing for 15 minutes using an agate pestle and mortar. A method of preparing a negative electrode mixture by mixing in this way is called dry mixing.

(Fabrication of half-cell)
A half-cell was also fabricated in a glove box with a dew point of about -70°C. A half cell was produced using a pellet production jig. The pellet production jig has a PEEK (polyetheretherketone) holder with an inner diameter of 10 mm and upper and lower punches with a diameter of 9.99 mm. The material of the upper and lower punches is die steel (SKD11 material).

A lower punch was inserted into the PEEK holder of the pellet production jig, and 110 mg of the solid electrolyte was put on the lower punch. Next, after the resin holder was vibrated to level the surface of the solid electrolyte, an upper punch was inserted onto the solid electrolyte and pressed with a load of about 4 KN using a pressing machine.

Next, the upper punch was pulled out, and 10 mg of the negative electrode mixture was put on the solid electrolyte. Next, after the PEEK holder was vibrated to level the surface of the negative electrode mixture, an upper punch was inserted onto the negative electrode mixture and pressed with a load of 3 KN using a pressing machine. Next, the lower punch was removed, a Li foil with a diameter of 10 mm was put on the solid electrolyte layer, and the lower punch was inserted. In this way, a half cell was produced in which the negative electrode mixture layer, the solid electrolyte layer, and the Li foil were laminated in this order.

Also, two stainless steel plates with a diameter of 50 mm and a thickness of 5 mm and two Bakelite (registered trademark) plates with a diameter of 50 mm and a thickness of 2 mm were prepared. Next, two stainless steel plates and two Bakelite (registered trademark) plates were each provided with four holes for passing screws. When the electrochemical cell, two stainless steel plates, and two Bakelite (registered trademark) plates are stacked, the holes for the screws are formed between the two stainless steel plates and the two Bakelite (registered trademark) plates. It was provided at a position that overlaps with the electrochemical cell in plan view and does not overlap with the electrochemical cell in plan view.

Thereafter, a stainless steel plate, a Bakelite (registered trademark) plate, a half cell, a Bakelite (registered trademark) plate, and a stainless steel plate were laminated in this order, and screws were inserted into the screw holes and tightened with a torque of 1 N·m. Thus, a half cell was obtained in which the upper and lower punches of the electrochemical cell were insulated by Bakelite® plates. Next, the half cell was placed in a constant temperature bath at 25° C. for 48 hours to stabilize the open circuit voltage.

Electrochemical characteristics of the negative electrode were evaluated using the half cell thus produced. The measurement was carried out by leaving the half cell in a constant temperature bath at 25°C. The C (see) rate was used for the notation of the charge/discharge current. nC (mA) is the current that can charge and discharge the nominal capacity (mAh) at 1/n (h). Since the nominal discharge capacity of the above graphite is 342 mAhg ⁻¹ , the nominal capacity of the half cell is “negative electrode mixture mass (mg)” / 1000 × “ratio of graphite in negative electrode mixture” × “nominal capacity of graphite (mAhg ⁻¹ )”=10/1000×0.67×342=2.29 mAh. Therefore, the current of 0.01C is 2.29mA*0.01*1000=22.9uA. It was charged to 5 mV (vs. Li/Li ⁺ ) at a current of 0.01 C and discharged to 3.0 V (vs. Li/Li ⁺ ) at a current of 0.01 C. The initial charge/discharge efficiency of the cell of Example 1 was 65%.

The initial charge/discharge efficiency was obtained by the following formula.
Initial charge/discharge efficiency (%) = discharge capacity (mAh) / charge capacity (mAh) x 100

Next, in a glove box, the half cell after charging and discharging was disassembled, the negative electrode mixture was taken out and cut, and the cross section was measured with a scanning electron microscope. Then, it was confirmed that an insulator was present between the negative electrode active material and the first compound. Also, the particle diameters of the negative electrode active material and the insulator were measured.

"Example 2 to Example 12"
Examples 2 to 12 are different from Example 1 in that the material used as the organic substance was changed. Some of Examples 2 to 12 employ wet mixing as a method for supporting organic matter on the negative electrode active material 34A (see Table 1). A half cell was produced in the same manner as for other configurations, and the initial charge/discharge efficiency was obtained under the same charge/discharge conditions as in Example 1.
In Example 2, fluoroethylene carbonate (FEC) was used as the organic substance.
In Example 3, vinylene carbonate (VC) was used as the organic substance.
In Example 4, propane sultone was used as the organic matter.
In Example 5, divinyl adipate was used as the organic substance.
In Example 6, vinyl acetate was used as the organic matter.
In Example 7, ethylene sulfide was used as the organic substance.
In Example 8, chloroethylene carbonate (CLEC) was used as the organic matter.
In Example 9, catechol carbonate was used as the organic matter.
In Example 10, propynyl methanesulfonate was used as the organic matter.
In Example 11, lithium bis[1,2-oxalato(2)-O,O']borate (LiBOB) was used as the organic material.
In Example 12, lithium difluoromono[1,2-dioxalato(2)-O,O']borate (LiDFOB) was used as the organic substance.

"Example 13"
Example 13 differs from Example 2 in that LiCl was added as a lithium salt to the negative electrode mixture. The mass ratio of the negative electrode active material 34A, the first compound 34B, the insulator 34C, and the lithium salt is 70 _: 29.25:0.68: _0.07 (=Gr: _Li2ZrSO4Cl4 :FEC:LiCl). did. A half cell was produced with the other configurations being the same, and the initial charge/discharge efficiency was determined under the same charge/discharge conditions as in Example 2.

"Example 14"
Example 14 differs from Example 2 in that Li _1.96 Zr _0.01 Cl ₂ was added as the second compound to the negative electrode mixture. The mass ratio of the negative electrode active material 34A, the first compound 34B, the organic substance 34C, and the second compound _34E is 70:29:0.75: _0.25 (= _Gr : _Li2ZrSO4Cl4 :FEC: _{Li2Zr0 .01} Cl ₂ ). A half cell was produced with the other configurations being the same, and the initial charge/discharge efficiency was determined under the same charge/discharge conditions as in Example 2.

"Examples 15-17"
Examples 15-17 differ from Example 2 in that the first compound and the solid electrolyte were changed. A half cell was produced with the other configurations being the same, and the initial charge/discharge efficiency was determined under the same charge/discharge conditions as in Example 2.
Example 15 used Li ₂ Zr(HCOO)Cl ₅ as the first compound.
Example 16 used Li ₂ Zr((COO) ₂ ) _0.5 Cl ₅ as the first compound.
Example 17 used Li ₂ Zr(CH ₃ COO)Cl ₅ as the first compound.

"Example 18"
Example 18 differs from Example 2 in that the negative electrode active material is changed to silicon, carbon black is added as a conductive agent, and LiPF ₆ is added as a lithium salt. The mass ratio of the negative electrode active material 34A, the conductive aid 34D, the first compound 34B, the organic substance 34C, and the lithium salt is 67:3:29.25:0.7: _0.05 (=Gr:CB: _Li2ZrSO4 Cl ₄ :FEC:LiPF ₆ ). A half cell was produced with the other configurations being the same, and the initial charge/discharge efficiency was determined under the same charge/discharge conditions as in Example 2.

"Comparative Example 1"
Comparative Example 1 differs from Example 1 in that the organic substance 34C was not added when the negative electrode mixture was produced. The mass ratio of the negative electrode active material 34A and the first compound 34B in the negative electrode mixture was 70:30. A half cell was produced in the same manner as for other configurations, and the initial charge/discharge efficiency was obtained under the same charge/discharge conditions as in Example 1.

The results of Examples 1 to 20 and Comparative Example 1 are summarized in Table 1 below. Gr in Table 1 represents graphite, and CB represents carbon black.

All of the cells using the negative electrodes of Examples 1 to 20 had higher initial charge-discharge efficiencies than the cells using the negative electrode of Comparative Example 1. That is, the initial charge/discharge efficiency was improved by adding an organic substance to the negative electrode mixture.

DESCRIPTION OF SYMBOLS 10... Solid electrolyte layer 20... Positive electrode 22... Positive electrode collector 24... Positive electrode mixture layer 30... Negative electrode 32... Negative electrode collector 34... Negative electrode mixture layer 34A... Negative electrode active material 34B... 1st compound, 34C... organic substance, 34D... conductive aid, 34E... second compound, 40... power generation element, 50... exterior body, 52... metal foil, 54... resin layer, 60, 62... terminal, 100... solid electrolyte battery

Claims (8)

a negative electrode active material, a first compound, and an organic material that forms an SEI film that protects the negative electrode active material at the interface with the negative electrode active material during an initial charging process, and that is supported by the negative electrode active material;
The first compound is A _a E _b G _c X _d (1),
In formula (1),
A is Li or at least one of Na and Ca and Li;
E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanides;
G is _{OH, BO2, BO3, BO4, B3O6 , B4O7 , CO3 , NO3 , AlO2 , SiO3} , _{SiO4 , Si2O7 , Si3O9} , _{Si4 O11} , _{Si6O18 ,} PO3 _{, PO4, P2O7 , P3O10 , SO3 , SO4 , SO5} , _{S2O3 , S2O4 , S2O5 , S2 O6} , _S2O7 , _S2O8 , _BF4 , _PF6 , BOB _, (COO) ₂ , N, _AlCl4 , _CF3SO3 , _{CH3COO , CF3COO} , _OOC- ( _CH2 ) ₂ -COO, OOC-CH2 _- COO, OOC-CH(OH)-CH(OH)-COO, OOC-CH ₍ OH)-CH2 _- COO, _{C6H5SO3 ,} OOC-CH=CH- COO _, OOC-CH=CH-COO, C(OH)( _CH2COOH ) _2COO , AsO4, _BiO4 , _CrO4 , _MnO4 , _PtF6 , PtCl6, _PtBr6 , _PtI6 , _{SbO4 ,} SeO ₄ , TeO ₄ , HCOO, and at least one group selected from the group consisting of O;
X is at least one element selected from the group consisting of F, Cl, Br, and I;
A negative electrode for a solid electrolyte battery that satisfies 0.5≦a<6, 0<b<2, 0≦<c≦6, and 0<d≦6.1. further comprising a second compound;
The second compound is Li _a E _b X _d (2), unlike the first compound,
In formula (2),
E is at least one element selected from the group consisting of Al, Sc, Y, Zr, Hf, and lanthanides;
X is at least one element selected from the group consisting of F, Cl, Br, and I;
2. The negative electrode for a solid electrolyte battery according to claim 1, which satisfies 0.5≦a<6, 0<b<2, and 0<d≦6.1. The organic substances include ethylene carbonate, fluoroethylene carbonate, vinylene carbonate, propane sultone, divinyl adipate, vinyl acetate, ethylene sulfide, chloroethylene carbonate, catechol carbonate, propynyl methanesulfonate, lithium bis[1,2-oxalato (2) -O,O']borate, lithium difluoromono[1,2-dioxalato(2)-O,O']borate, or a polymer thereof, claim 1 3. The negative electrode for a solid electrolyte battery according to 2 above. 4. The negative electrode for a solid electrolyte battery according to claim 1, further comprising a lithium salt having a molecular weight smaller than that of said first compound. 5. The negative electrode for a solid electrolyte battery according to claim 1, wherein said organic matter is solid at room temperature. Further comprising the SEI coating covering the negative electrode active material,
The SEI coating includes an organic SEI coating formed at the interface between the organic substance and the negative electrode active material, and an inorganic SEI coating formed between the first compound and the negative electrode active material, The negative electrode for a solid electrolyte battery according to any one of claims 1 to 5. A solid comprising a solid electrolyte battery negative electrode according to any one of claims 1 to 6, a positive electrode, and a solid electrolyte layer between the solid electrolyte battery negative electrode and the positive electrode and containing a solid electrolyte electrolyte battery. 8. The solid electrolyte battery according to claim 7, wherein said solid electrolyte is the same as said first compound.

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